The proc file system is a pseudo-file system which is used as an inter-
       face to kernel data structures.  It is commonly mounted at /proc.  Most
       of  it  is  read-only,  but  some  files  allow  kernel variables to be

       The following outline gives a quick tour through the /proc hierarchy.

              There is a numerical subdirectory for each running process;  the
              subdirectory is named by the process ID.  Each such subdirectory
              contains the following pseudo-files and directories.

       /proc/[pid]/auxv (since 2.6.0-test7)
              This contains the contents of the  ELF  interpreter  information
              passed  to the process at exec time.  The format is one unsigned
              long ID plus one unsigned long value for each entry.   The  last
              entry contains two zeros.

              This holds the complete command line for the process, unless the
              process is a zombie.  In the latter case, there  is  nothing  in
              this  file:  that  is, a read on this file will return 0 charac-
              ters.  The command-line arguments appear in this file as  a  set
              of  strings  separated by null bytes ('\0'), with a further null
              byte after the last string.

       /proc/[pid]/coredump_filter (since kernel 2.6.23)
              See core(5).

       /proc/[pid]/cpuset (since kernel 2.6.12)
              See cpuset(7).

              This is a symbolic link to the current working directory of  the
              process.   To  find out the current working directory of process
              20, for instance, you can do this:

                  $ cd /proc/20/cwd; /bin/pwd

              Note that the pwd command is often a shell built-in,  and  might
              not work properly.  In bash(1), you may use pwd -P.

              In  a  multithreaded process, the contents of this symbolic link
              are not available if the  main  thread  has  already  terminated
              (typically by calling pthread_exit(3)).

              This file contains the environment for the process.  The entries
              are separated by null bytes ('\0'), and there may be a null byte
              at  the  end.   Thus, to print out the environment of process 1,
              you would do:

              Under  Linux 2.0 and earlier /proc/[pid]/exe is a pointer to the
              binary which was executed, and appears as a  symbolic  link.   A
              readlink(2)  call  on this file under Linux 2.0 returns a string
              in the format:


              For example, [0301]:1502 would be inode 1502 on device major  03
              (IDE,  MFM,  etc. drives) minor 01 (first partition on the first

              find(1) with the -inum option can be used to locate the file.

              This is a subdirectory containing one entry for each file  which
              the process has open, named by its file descriptor, and which is
              a symbolic link to the actual file.  Thus, 0 is standard  input,
              1 standard output, 2 standard error, etc.

              In  a  multithreaded process, the contents of this directory are
              not available if the main thread has already  terminated  (typi-
              cally by calling pthread_exit(3)).

              Programs  that  will take a filename as a command-line argument,
              but will not take input from standard input if  no  argument  is
              supplied,  or that write to a file named as a command-line argu-
              ment, but will not send their output to standard  output  if  no
              argument  is  supplied, can nevertheless be made to use standard
              input or standard out using /proc/[pid]/fd.  For example, assum-
              ing  that -i is the flag designating an input file and -o is the
              flag designating an output file:

                  $ foobar -i /proc/self/fd/0 -o /proc/self/fd/1 ...

              and you have a working filter.

              /proc/self/fd/N is approximately the same as /dev/fd/N  in  some
              UNIX and UNIX-like systems.  Most Linux MAKEDEV scripts symboli-
              cally link /dev/fd to /proc/self/fd, in fact.

              Most systems provide symbolic links /dev/stdin, /dev/stdout, and
              /dev/stderr, which respectively link to the files 0, 1, and 2 in
              /proc/self/fd.  Thus the example command above could be  written

                  $ foobar -i /dev/stdin -o /dev/stdout ...

       /proc/[pid]/fdinfo/ (since kernel 2.6.22)
              This  is a subdirectory containing one entry for each file which
              the process has open, named by its file  descriptor.   The  con-
              tents  of  each file can be read to obtain information about the
              corresponding file descriptor, for example:

                  $ cat /proc/12015/fdinfo/4

              surement for each of the process's resource  limits  (see  getr-
              limit(2)).   The  file is protected to only allow reading by the
              real UID of the process.

              A file containing the currently mapped memory regions and  their
              access permissions.

              The format is:

              address           perms offset  dev   inode   pathname
              08048000-08056000 r-xp 00000000 03:0c 64593   /usr/sbin/gpm
              08056000-08058000 rw-p 0000d000 03:0c 64593   /usr/sbin/gpm
              08058000-0805b000 rwxp 00000000 00:00 0
              40000000-40013000 r-xp 00000000 03:0c 4165    /lib/
              40013000-40015000 rw-p 00012000 03:0c 4165    /lib/
              4001f000-40135000 r-xp 00000000 03:0c 45494   /lib/
              40135000-4013e000 rw-p 00115000 03:0c 45494   /lib/
              4013e000-40142000 rw-p 00000000 00:00 0
              bffff000-c0000000 rwxp 00000000 00:00 0

              where  "address"  is  the  address  space in the process that it
              occupies, "perms" is a set of permissions:

                   r = read
                   w = write
                   x = execute
                   s = shared
                   p = private (copy on write)

              "offset" is the offset into  the  file/whatever,  "dev"  is  the
              device  (major:minor),  and "inode" is the inode on that device.
              0 indicates that no inode is associated with the memory  region,
              as the case would be with BSS (uninitialized data).

              Under Linux 2.0 there is no field giving pathname.

              This  file can be used to access the pages of a process's memory
              through open(2), read(2), and lseek(2).

       /proc/[pid]/mountinfo (since Linux 2.6.26)
              This file contains information about mount points.  It  contains
              lines of the form:

              36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
              (1)(2)(3)   (4)   (5)      (6)      (7)   (8) (9)   (10)         (11)

              The  numbers  in  parentheses  are  labels  for the descriptions

              (1)  mount ID: unique identifier of the  mount  (may  be  reused
                   after umount(2)).

              (7)  optional   fields:   zero   or  more  fields  of  the  form

              (8)  separator: marks the end of the optional fields.

              (9)  file  system  type:  name  of  file  system  in  the   form

              (10) mount source: file system-specific information or "none".

              (11) super options: per-super block options.

              Parsers  should  ignore  all unrecognized optional fields.  Cur-
              rently the possible optional fields are:

                   shared:X          mount is shared in peer group X

                   master:X          mount is slave to peer group X

                   propagate_from:X  mount is slave and  receives  propagation
                                     from peer group X (*)

                   unbindable        mount is unbindable

              (*)  X  is  the  closest dominant peer group under the process's
              root.  If X is the immediate master of the mount, or if there is
              no  dominant peer group under the same root, then only the "mas-
              ter:X" field is present and not the "propagate_from:X" field.

              For  more  information  on  mount  propagation  see:  Documenta-
              tion/filesystems/sharedsubtree.txt in the kernel source tree.

       /proc/[pid]/mounts (since Linux 2.4.19)
              This  is a list of all the file systems currently mounted in the
              process's mount namespace.  The format of  this  file  is  docu-
              mented  in  fstab(5).  Since kernel version 2.6.15, this file is
              pollable: after opening the file for reading, a change  in  this
              file  (i.e., a file system mount or unmount) causes select(2) to
              mark  the  file  descriptor  as  readable,   and   poll(2)   and
              epoll_wait(2) mark the file as having an error condition.

       /proc/[pid]/mountstats (since Linux 2.6.17)
              This  file exports information (statistics, configuration infor-
              mation) about the mount points  in  the  process's  name  space.
              Lines in this file have the form:

              device /dev/sda7 mounted on /home with fstype ext3 [statistics]
              (       1      )            ( 2 )             (3 ) (4)

              The fields in each line are:

              (1)  The  name  of the mounted device (or "nodevice" if there is
                   no corresponding device).

              that  supports  being  manipulated by setns(2).  For information
              about namespaces, see clone(2).

       /proc/[pid]/ns/ipc (since Linux 3.0)
              Bind mounting this file (see mount(2)) to somewhere else in  the
              filesystem  keeps  the IPC namespace of the process specified by
              pid alive even if all processes currently in the namespace  ter-

              Opening this file returns a file handle for the IPC namespace of
              the process specified by pid.  As long as this  file  descriptor
              remains  open,  the IPC namespace will remain alive, even if all
              processes in the namespace terminate.  The file  descriptor  can
              be passed to setns(2).

       /proc/[pid]/ns/net (since Linux 3.0)
              Bind  mounting this file (see mount(2)) to somewhere else in the
              filesystem keeps the network namespace of the process  specified
              by pid alive even if all processes in the namespace terminate.

              Opening  this  file returns a file handle for the network names-
              pace of the process specified by pid.   As  long  as  this  file
              descriptor  remains  open,  the  network  namespace  will remain
              alive, even if all processes in the  namespace  terminate.   The
              file descriptor can be passed to setns(2).

       /proc/[pid]/ns/uts (since Linux 3.0)
              Bind  mounting this file (see mount(2)) to somewhere else in the
              filesystem keeps the UTS namespace of the process  specified  by
              pid  alive even if all processes currently in the namespace ter-

              Opening this file returns a file handle for the UTS namespace of
              the  process  specified by pid.  As long as this file descriptor
              remains open, the UTS namespace will remain alive, even  if  all
              processes  in  the namespace terminate.  The file descriptor can
              be passed to setns(2).

       /proc/[pid]/numa_maps (since Linux 2.6.14)
              See numa(7).

       /proc/[pid]/oom_adj (since Linux 2.6.11)
              This file can be used to adjust the score used to  select  which
              process  should  be  killed in an out-of-memory (OOM) situation.
              The kernel uses this value for  a  bit-shift  operation  of  the
              process's  oom_score value: valid values are in the range -16 to
              +15, plus the special  value  -17,  which  disables  OOM-killing
              altogether  for  this  process.   A positive score increases the
              likelihood of this process being killed  by  the  OOM-killer;  a
              negative  score decreases the likelihood.  The default value for
              this file is 0; a new process inherits its parent's oom_adj set-
              ting.  A process must be privileged (CAP_SYS_RESOURCE) to update
              this file.

                a lot of CPU time (-);

              * whether the process has a low nice value (i.e., > 0) (+);

              * whether the process is privileged (-); and

              * whether the process is making direct hardware access (-).

              The  oom_score  also reflects the bit-shift adjustment specified
              by the oom_adj setting for the process.

              UNIX and Linux support the idea of a  per-process  root  of  the
              file  system,  set by the chroot(2) system call.  This file is a
              symbolic link that points to the process's root  directory,  and
              behaves as exe, fd/*, etc. do.

              In  a  multithreaded process, the contents of this symbolic link
              are not available if the  main  thread  has  already  terminated
              (typically by calling pthread_exit(3)).

       /proc/[pid]/smaps (since Linux 2.6.14)
              This  file  shows  memory  consumption for each of the process's
              mappings.  For each of mappings there is a series of lines  such
              as the following:

                  08048000-080bc000 r-xp 00000000 03:02 13130      /bin/bash
                  Size:               464 kB
                  Rss:                424 kB
                  Shared_Clean:       424 kB
                  Shared_Dirty:         0 kB
                  Private_Clean:        0 kB
                  Private_Dirty:        0 kB

              The  first  of these lines shows the same information as is dis-
              played for the mapping in /proc/[pid]/maps.  The remaining lines
              show  the size of the mapping, the amount of the mapping that is
              currently resident in RAM, the number of clean and dirty  shared
              pages  in the mapping, and the number of clean and dirty private
              pages in the mapping.

              This file is only present if the CONFIG_MMU kernel configuration
              option is enabled.

              Status  information  about  the process.  This is used by ps(1).
              It is defined in /usr/src/linux/fs/proc/array.c.

              The fields, in order, with their proper scanf(3)  format  speci-
              fiers, are:

              pid %d      The process ID.

              comm %s     The  filename  of  the  executable,  in parentheses.

              session %d  The session ID of the process.

              tty_nr %d   The controlling terminal of the process.  (The minor
                          device number is contained  in  the  combination  of
                          bits 31 to 20 and 7 to 0; the major device number is
                          in bits 15 to 8.)

              tpgid %d    The ID of the foreground process group of  the  con-
                          trolling terminal of the process.

              flags %u (%lu before Linux 2.6.22)
                          The kernel flags word of the process.  For bit mean-
                          ings,  see  the  PF_*  defines  in  <linux/sched.h>.
                          Details depend on the kernel version.

              minflt %lu  The  number  of  minor  faults  the process has made
                          which have not required loading a memory  page  from

              cminflt %lu The  number  of  minor  faults  that  the  process's
                          waited-for children have made.

              majflt %lu  The number of major  faults  the  process  has  made
                          which have required loading a memory page from disk.

              cmajflt %lu The  number  of  major  faults  that  the  process's
                          waited-for children have made.

              utime %lu   Amount of time that this process has been  scheduled
                          in  user  mode,  measured  in clock ticks (divide by
                          sysconf(_SC_CLK_TCK).   This  includes  guest  time,
                          guest_time  (time  spent  running a virtual CPU, see
                          below), so that applications that are not  aware  of
                          the  guest  time  field  do  not lose that time from
                          their calculations.

              stime %lu   Amount of time that this process has been  scheduled
                          in  kernel  mode, measured in clock ticks (divide by

              cutime %ld  Amount of time that this process's waited-for  chil-
                          dren  have  been scheduled in user mode, measured in
                          clock ticks (divide by  sysconf(_SC_CLK_TCK).   (See
                          also   times(2).)    This   includes   guest   time,
                          cguest_time (time spent running a virtual  CPU,  see

              cstime %ld  Amount  of time that this process's waited-for chil-
                          dren have been scheduled in kernel mode, measured in
                          clock ticks (divide by sysconf(_SC_CLK_TCK).

              priority %ld
                          (Explanation  for Linux 2.6) For processes running a
                          the scheduler weighting given to this process.

              nice %ld    The nice value (see setpriority(2)), a value in  the
                          range 19 (low priority) to -20 (high priority).

              num_threads %ld
                          Number of threads in this process (since Linux 2.6).
                          Before kernel 2.6, this field was hard coded to 0 as
                          a placeholder for an earlier removed field.

              itrealvalue %ld
                          The  time in jiffies before the next SIGALRM is sent
                          to the process due to an interval timer.  Since ker-
                          nel  2.6.17, this field is no longer maintained, and
                          is hard coded as 0.

              starttime %llu (was %lu before Linux 2.6)
                          The time in jiffies the process started after system

              vsize %lu   Virtual memory size in bytes.

              rss %ld     Resident  Set  Size: number of pages the process has
                          in real memory.  This is just the pages which  count
                          toward  text,  data,  or stack space.  This does not
                          include pages which have not been demand-loaded  in,
                          or which are swapped out.

              rsslim %lu  Current  soft  limit  in  bytes  on  the  rss of the
                          process; see the description of RLIMIT_RSS  in  get-

              startcode %lu
                          The address above which program text can run.

              endcode %lu The address below which program text can run.

              startstack %lu
                          The  address  of  the  start  (i.e.,  bottom) of the

              kstkesp %lu The current value of ESP (stack pointer),  as  found
                          in the kernel stack page for the process.

              kstkeip %lu The current EIP (instruction pointer).

              signal %lu  The  bitmap of pending signals, displayed as a deci-
                          mal number.  Obsolete, because it does  not  provide
                          information     on     real-time     signals;    use
                          /proc/[pid]/status instead.

              blocked %lu The bitmap of blocked signals, displayed as a  deci-
                          mal  number.   Obsolete, because it does not provide
                          information    on     real-time     signals;     use
                          /proc/[pid]/status instead.

              wchan %lu   This  is the "channel" in which the process is wait-
                          ing.  It is the address of a system call, and can be
                          looked  up in a namelist if you need a textual name.
                          (If you have an up-to-date /etc/psdatabase, then try
                          ps -l to see the WCHAN field in action.)

              nswap %lu   Number of pages swapped (not maintained).

              cnswap %lu  Cumulative  nswap  for  child  processes  (not main-

              exit_signal %d (since Linux 2.1.22)
                          Signal to be sent to parent when we die.

              processor %d (since Linux 2.2.8)
                          CPU number last executed on.

              rt_priority %u (since Linux 2.5.19; was %lu before Linux 2.6.22)
                          Real-time scheduling priority, a number in the range
                          1  to  99  for processes scheduled under a real-time
                          policy,  or  0,  for  non-real-time  processes  (see

              policy %u (since Linux 2.5.19; was %lu before Linux 2.6.22)
                          Scheduling   policy   (see   sched_setscheduler(2)).
                          Decode using the SCHED_* constants in linux/sched.h.

              delayacct_blkio_ticks %llu (since Linux 2.6.18)
                          Aggregated block I/O delays, measured in clock ticks

              guest_time %lu (since Linux 2.6.24)
                          Guest time of the process (time spent running a vir-
                          tual CPU for a guest operating system), measured  in
                          clock ticks (divide by sysconf(_SC_CLK_TCK).

              cguest_time %ld (since Linux 2.6.24)
                          Guest  time  of  the process's children, measured in
                          clock ticks (divide by sysconf(_SC_CLK_TCK).

              Provides information about memory usage, measured in pages.  The
              columns are:

                  size       total program size
                             (same as VmSize in /proc/[pid]/status)
                  resident   resident set size
                             (same as VmRSS in /proc/[pid]/status)
                  share      shared pages (from shared mappings)
                  text       text (code)
                  lib        library (unused in Linux 2.6)
                  data       data + stack
                  PPid:   3452
                  TracerPid:      0
                  Uid:    1000    1000    1000    1000
                  Gid:    100     100     100     100
                  FDSize: 256
                  Groups: 16 33 100
                  VmPeak:     9136 kB
                  VmSize:     7896 kB
                  VmLck:         0 kB
                  VmHWM:      7572 kB
                  VmRSS:      6316 kB
                  VmData:     5224 kB
                  VmStk:        88 kB
                  VmExe:       572 kB
                  VmLib:      1708 kB
                  VmPTE:        20 kB
                  Threads:        1
                  SigQ:   0/3067
                  SigPnd: 0000000000000000
                  ShdPnd: 0000000000000000
                  SigBlk: 0000000000010000
                  SigIgn: 0000000000384004
                  SigCgt: 000000004b813efb
                  CapInh: 0000000000000000
                  CapPrm: 0000000000000000
                  CapEff: 0000000000000000
                  CapBnd: ffffffffffffffff
                  Cpus_allowed:   00000001
                  Cpus_allowed_list:      0
                  Mems_allowed:   1
                  Mems_allowed_list:      0
                  voluntary_ctxt_switches:        150
                  nonvoluntary_ctxt_switches:     545

              The fields are as follows:

              * Name: Command run by this process.

              * State: Current state of the process.  One of "R (running)", "S
                (sleeping)", "D (disk  sleep)",  "T  (stopped)",  "T  (tracing
                stop)", "Z (zombie)", or "X (dead)".

              * Tgid: Thread group ID (i.e., Process ID).

              * Pid: Thread ID (see gettid(2)).

              * PPid: PID of parent process.

              * TracerPid: PID of process tracing this process (0 if not being

              * Uid, Gid: Real, effective, saved set,  and  file  system  UIDs

              * VmRSS: Resident set size.

              * VmData, VmStk, VmExe: Size of data, stack, and text segments.

              * VmLib: Shared library code size.

              * VmPTE: Page table entries size (since Linux 2.6.10).

              * Threads: Number of threads in process containing this thread.

              * SigQ:  This  field  contains  two slash-separated numbers that
                relate to queued signals for the real user ID of this process.
                The  first  of these is the number of currently queued signals
                for this real user ID, and the second is the resource limit on
                the  number  of  queued  signals  for  this  process  (see the
                description of RLIMIT_SIGPENDING in getrlimit(2)).

              * SigPnd, ShdPnd: Number of signals pending for thread  and  for
                process as a whole (see pthreads(7) and signal(7)).

              * SigBlk,   SigIgn,   SigCgt:  Masks  indicating  signals  being
                blocked, ignored, and caught (see signal(7)).

              * CapInh, CapPrm,  CapEff:  Masks  of  capabilities  enabled  in
                inheritable,  permitted,  and  effective  sets  (see capabili-

              * CapBnd: Capability Bounding  set  (since  kernel  2.6.26,  see

              * Cpus_allowed:  Mask  of  CPUs  on  which  this process may run
                (since Linux 2.6.24, see cpuset(7)).

              * Cpus_allowed_list: Same as  previous,  but  in  "list  format"
                (since Linux 2.6.26, see cpuset(7)).

              * Mems_allowed:  Mask  of  memory  nodes allowed to this process
                (since Linux 2.6.24, see cpuset(7)).

              * Mems_allowed_list: Same as  previous,  but  in  "list  format"
                (since Linux 2.6.26, see cpuset(7)).

              * voluntary_context_switches,     nonvoluntary_context_switches:
                Number of voluntary and involuntary  context  switches  (since
                Linux 2.6.23).

       /proc/[pid]/task (since Linux 2.6.0-test6)
              This  is  a  directory  that  contains one subdirectory for each
              thread in the process.  The name of  each  subdirectory  is  the
              numerical  thread  ID  ([tid])  of  the  thread (see gettid(2)).
              Within each of these subdirectories, there is  a  set  of  files
              with the same names and contents as under the /proc/[pid] direc-
              tories.  For attributes that are shared by all threads, the con-
              tents  for each of the files under the task/[tid] subdirectories
              minated (typically by calling pthread_exit(3)).

              Advanced power management version and battery  information  when
              CONFIG_APM is defined at kernel compilation time.

              Contains subdirectories for installed busses.

              Subdirectory  for  PCMCIA  devices  when CONFIG_PCMCIA is set at
              kernel compilation time.


              Contains various bus subdirectories and pseudo-files  containing
              information  about  PCI  busses,  installed  devices, and device
              drivers.  Some of these files are not ASCII.

              Information about PCI devices.  They  may  be  accessed  through
              lspci(8) and setpci(8).

              Arguments  passed  to the Linux kernel at boot time.  Often done
              via a boot manager such as lilo(8) or grub(8).

       /proc/config.gz (since Linux 2.6)
              This file exposes the configuration options that  were  used  to
              build  the  currently running kernel, in the same format as they
              would be shown in the .config file that resulted when  configur-
              ing  the  kernel  (using make xconfig, make config, or similar).
              The file contents are compressed;  view  or  search  them  using
              zcat(1), zgrep(1), etc.  As long as no changes have been made to
              the following file, the contents of /proc/config.gz are the same
              as those provided by :

                  cat /lib/modules/$(uname -r)/build/.config

              /proc/config.gz  is  only  provided  if the kernel is configured
              with CONFIG_IKCONFIG_PROC.

              This is a collection of CPU and  system  architecture  dependent
              items,  for  each  supported architecture a different list.  Two
              common  entries  are  processor  which  gives  CPU  number   and
              bogomips;  a  system  constant  that is calculated during kernel
              initialization.  SMP machines have information for each CPU.

              Text listing of major numbers and device groups.   This  can  be
              used by MAKEDEV scripts for consistency with the kernel.

              List of the execution domains (ABI personalities).

              Frame buffer information when CONFIG_FB is defined during kernel

              A  text  listing  of the file systems which are supported by the
              kernel, namely file systems which were compiled into the  kernel
              or  whose  kernel  modules  are  currently  loaded.   (See  also
              filesystems(5).)  If a file system is marked with "nodev",  this
              means  that  it  does  not  require a block device to be mounted
              (e.g., virtual file system, network file system).

              Incidentally, this file may be used by  mount(8)  when  no  file
              system  is  specified and it didn't manage to determine the file
              system type.  Then file systems contained in this file are tried
              (excepted those that are marked with "nodev").

              Empty subdirectory.

              This  directory  exists  on systems with the IDE bus.  There are
              directories for each IDE channel  and  attached  device.   Files

                  cache              buffer size in KB
                  capacity           number of sectors
                  driver             driver version
                  geometry           physical and logical geometry
                  identify           in hexadecimal
                  media              media type
                  model              manufacturer's model number
                  settings           drive settings
                  smart_thresholds   in hexadecimal
                  smart_values       in hexadecimal

              The  hdparm(8)  utility provides access to this information in a
              friendly format.

              This is used to record the number of interrupts per CPU  per  IO
              device.   Since  Linux 2.6.24, for the i386 and x86_64 architec-
              tures, at least, this also includes interrupts internal  to  the
              system  (that is, not associated with a device as such), such as
              NMI (nonmaskable interrupt), LOC (local  timer  interrupt),  and
              for  SMP  systems,  TLB (TLB flush interrupt), RES (rescheduling
              interrupt), CAL (remote function call interrupt),  and  possibly
              others.  Very easy to read formatting, done in ASCII.

              I/O memory map in Linux 2.4.
              This  file  represents  the physical memory of the system and is
              stored in the ELF core file format.  With this pseudo-file,  and
              an unstripped kernel (/usr/src/linux/vmlinux) binary, GDB can be
              used to examine the current state of any kernel data structures.

              The total length of the file is  the  size  of  physical  memory
              (RAM) plus 4KB.

              This  file  can  be used instead of the syslog(2) system call to
              read kernel messages.  A process must have superuser  privileges
              to  read  this file, and only one process should read this file.
              This file should not be read if  a  syslog  process  is  running
              which uses the syslog(2) system call facility to log kernel mes-

              Information in this file is retrieved with the dmesg(1) program.

       /proc/ksyms (Linux 1.1.23-2.5.47)
              See /proc/kallsyms.

              The first three fields in this file  are  load  average  figures
              giving  the number of jobs in the run queue (state R) or waiting
              for disk I/O (state D) averaged over 1, 5, and 15 minutes.  They
              are  the same as the load average numbers given by uptime(1) and
              other programs.  The fourth field consists of two numbers  sepa-
              rated  by a slash (/).  The first of these is the number of cur-
              rently  executing   kernel   scheduling   entities   (processes,
              threads); this will be less than or equal to the number of CPUs.
              The value after the slash is the  number  of  kernel  scheduling
              entities that currently exist on the system.  The fifth field is
              the PID of the process that was most  recently  created  on  the

              This  file  shows current file locks (flock(2) and fcntl(2)) and
              leases (fcntl(2)).

       /proc/malloc (only up to and including Linux 2.2)
              This file is only present  if  CONFIG_DEBUG_MALLOC  was  defined
              during compilation.

              This  file  reports statistics about memory usage on the system.
              It is used by free(1) to report the amount of free and used mem-
              ory (both physical and swap) on the system as well as the shared
              memory and buffers used by the kernel.

              A text list of the modules that have been loaded by the  system.
              See also lsmod(8).

              various  net  pseudo-files, all of which give the status of some
              part of the networking layer.  These files contain ASCII  struc-
              tures  and  are,  therefore, readable with cat(1).  However, the
              standard netstat(8) suite provides much cleaner access to  these

              This  holds  an ASCII readable dump of the kernel ARP table used
              for address resolutions.  It will show both dynamically  learned
              and preprogrammed ARP entries.  The format is:

        IP address     HW type   Flags     HW address          Mask   Device   0x1       0x2       00:50:BF:25:68:F3   *      eth0  0x1       0xc       00:00:00:00:00:00   *      eth0

              Here "IP address" is the IPv4 address of the machine and the "HW
              type" is the hardware type of the  address  from  RFC 826.   The
              flags are the internal flags of the ARP structure (as defined in
              /usr/include/linux/if_arp.h) and the "HW address"  is  the  data
              link layer mapping for that IP address if it is known.

              The  dev pseudo-file contains network device status information.
              This gives the number of received and sent packets,  the  number
              of  errors and collisions and other basic statistics.  These are
              used by the ifconfig(8) program to report  device  status.   The
              format is:

 Inter-|   Receive                                                |  Transmit
  face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
     lo: 2776770   11307    0    0    0     0          0         0  2776770   11307    0    0    0     0       0          0
   eth0: 1215645    2751    0    0    0     0          0         0  1782404    4324    0    0    0   427       0          0
   ppp0: 1622270    5552    1    0    0     0          0         0   354130    5669    0    0    0     0       0          0
   tap0:    7714      81    0    0    0     0          0         0     7714      81    0    0    0     0       0          0

              Defined in /usr/src/linux/net/core/dev_mcast.c:
                   indx interface_name  dmi_u dmi_g dmi_address
                   2    eth0            1     0     01005e000001
                   3    eth1            1     0     01005e000001
                   4    eth2            1     0     01005e000001

              Internet     Group     Management    Protocol.     Defined    in

              This file uses the same format as the arp file and contains  the
              current reverse mapping database used to provide rarp(8) reverse
              address lookup services.  If RARP is  not  configured  into  the
              kernel, this file will not be present.

              UDP management information bases for an SNMP agent.

              Holds a dump of the TCP socket table.  Much of  the  information
              is  not of use apart from debugging.  The "sl" value is the ker-
              nel hash slot for the socket, the "local_address" is  the  local
              address  and  port number pair.  The "rem_address" is the remote
              address and port number pair (if connected).  "St" is the inter-
              nal status of the socket.  The "tx_queue" and "rx_queue" are the
              outgoing and incoming data  queue  in  terms  of  kernel  memory
              usage.  The "tr", "tm->when", and "rexmits" fields hold internal
              information of the kernel socket state and are only  useful  for
              debugging.   The "uid" field holds the effective UID of the cre-
              ator of the socket.

              Holds a dump of the UDP socket table.  Much of  the  information
              is  not of use apart from debugging.  The "sl" value is the ker-
              nel hash slot for the socket, the "local_address" is  the  local
              address  and  port number pair.  The "rem_address" is the remote
              address and port number pair (if connected). "St" is the  inter-
              nal status of the socket.  The "tx_queue" and "rx_queue" are the
              outgoing and incoming data  queue  in  terms  of  kernel  memory
              usage.   The "tr", "tm->when", and "rexmits" fields are not used
              by UDP.  The "uid" field holds the effective UID of the  creator
              of the socket.  The format is:

 sl  local_address rem_address   st tx_queue rx_queue tr rexmits  tm->when uid
  1: 01642C89:0201 0C642C89:03FF 01 00000000:00000001 01:000071BA 00000000 0
  1: 00000000:0801 00000000:0000 0A 00000000:00000000 00:00000000 6F000100 0
  1: 00000000:0201 00000000:0000 0A 00000000:00000000 00:00000000 00000000 0

              Lists  the  UNIX  domain  sockets  present within the system and
              their status.  The format is:
              Num RefCount Protocol Flags    Type St Path
               0: 00000002 00000000 00000000 0001 03
               1: 00000001 00000000 00010000 0001 01 /dev/printer

              Here "Num" is the kernel table slot number,  "RefCount"  is  the
              number of users of the socket, "Protocol" is currently always 0,
              "Flags" represent the internal kernel flags holding  the  status
              of the socket.  Currently, type is always "1" (UNIX domain data-
              gram sockets are not yet supported in the kernel).  "St" is  the
              internal state of the socket and Path is the bound path (if any)
              of the socket.

              Contains major and minor numbers of each partition  as  well  as
              number of blocks and partition name.

              This  is  a  listing of all PCI devices found during kernel ini-
              tialization and their configuration.
              host in this system, all of which give the status of  some  part
              of  the SCSI IO subsystem.  These files contain ASCII structures
              and are, therefore, readable with cat(1).

              You can also write to some of the files to reconfigure the  sub-
              system or switch certain features on or off.

              This  is a listing of all SCSI devices known to the kernel.  The
              listing is similar to the one seen  during  bootup.   scsi  cur-
              rently  supports only the add-single-device command which allows
              root to add a hotplugged device to the list of known devices.

              The command

                  echo 'scsi add-single-device 1 0 5 0' > /proc/scsi/scsi

              will cause host scsi1 to scan on SCSI channel 0 for a device  on
              ID  5 LUN 0.  If there is already a device known on this address
              or the address is invalid, an error will be returned.

              [drivername]  can  currently  be  NCR53c7xx,  aha152x,  aha1542,
              aha1740, aic7xxx, buslogic, eata_dma, eata_pio, fdomain, in2000,
              pas16, qlogic, scsi_debug, seagate, t128,  u15-24f,  ultrastore,
              or  wd7000.  These directories show up for all drivers that reg-
              istered at least one SCSI HBA.   Every  directory  contains  one
              file  per  registered  host.  Every host-file is named after the
              number the host was assigned during initialization.

              Reading these files will usually show driver and host configura-
              tion, statistics, etc.

              Writing  to  these  files  allows  different things on different
              hosts.  For example, with the latency  and  nolatency  commands,
              root  can  switch on and off command latency measurement code in
              the eata_dma driver.  With the lockup and unlock commands,  root
              can control bus lockups simulated by the scsi_debug driver.

              This  directory  refers  to the process accessing the /proc file
              system, and is identical to the /proc  directory  named  by  the
              process ID of the same process.

              Information  about  kernel caches.  Since Linux 2.6.16 this file
              is only present if the CONFIG_SLAB kernel  configuration  option
              is enabled.  The columns in /proc/slabinfo are:

                     sysconf(_SC_CLK_TCK) to obtain the right value), that the
                     system  spent  in  user mode, user mode with low priority
                     (nice), system mode, and  the  idle  task,  respectively.
                     The  last  value should be USER_HZ times the second entry
                     in the uptime pseudo-file.

                     In Linux 2.6 this line includes three additional columns:
                     iowait - time waiting for I/O to complete (since 2.5.41);
                     irq -  time  servicing  interrupts  (since  2.6.0-test4);
                     softirq - time servicing softirqs (since 2.6.0-test4).

                     Since  Linux  2.6.11,  there is an eighth column, steal -
                     stolen time, which is the time spent in  other  operating
                     systems when running in a virtualized environment

                     Since Linux 2.6.24, there is a ninth column, guest, which
                     is the time spent running a virtual CPU for guest operat-
                     ing systems under the control of the Linux kernel.

              page 5741 1808
                     The  number  of  pages the system paged in and the number
                     that were paged out (from disk).

              swap 1 0
                     The number of swap pages that have been  brought  in  and

              intr 1462898
                     This  line shows counts of interrupts serviced since boot
                     time, for each of the possible  system  interrupts.   The
                     first  column  is  the  total of all interrupts serviced;
                     each subsequent column is  the  total  for  a  particular

              disk_io: (2,0):(31,30,5764,1,2) (3,0):...
                     (major,disk_idx):(noinfo,     read_io_ops,     blks_read,
                     write_io_ops, blks_written)
                     (Linux 2.4 only)

              ctxt 115315
                     The number of context switches that the system underwent.

              btime 769041601
                     boot  time,  in  seconds  since  the  Epoch,   1970-01-01
                     00:00:00 +0000 (UTC).

              processes 86031
                     Number of forks since boot.

              procs_running 6
                     Number  of  processes  in  runnable state.  (Linux 2.5.45

              procs_blocked 2

       /proc/sys/abi (since Linux 2.4.10)
              This directory may contain files with application binary  infor-
              mation.  See the kernel source file Documentation/sysctl/abi.txt
              for more information.

              This directory may be empty.

              This  directory  contains  device-specific  information   (e.g.,
              dev/cdrom/info).  On some systems, it may be empty.

              This  directory contains the files and subdirectories for kernel
              variables related to file systems.

              Documentation for files in this directory can be  found  in  the
              kernel sources in Documentation/binfmt_misc.txt.

       /proc/sys/fs/dentry-state (since Linux 2.2)
              This file contains information about the status of the directory
              cache (dcache).   The  file  contains  six  numbers,  nr_dentry,
              nr_unused,   age_limit   (age  in  seconds),  want_pages  (pages
              requested by system) and two dummy values.

              * nr_dentry  is  the  number  of  allocated   dentries   (dcache
                entries).  This field is unused in Linux 2.2.

              * nr_unused is the number of unused dentries.

              * age_limit is the age in seconds after which dcache entries can
                be reclaimed when memory is short.

              * want_pages   is   nonzero   when   the   kernel   has   called
                shrink_dcache_pages() and the dcache isn't pruned yet.

              This file can be used to disable or enable the dnotify interface
              described in fcntl(2) on a system-wide basis.  A value of  0  in
              this file disables the interface, and a value of 1 enables it.

              This file shows the maximum number of cached disk quota entries.
              On some (2.4) systems, it is not present.  If the number of free
              cached  disk quota entries is very low and you have some awesome
              number of simultaneous system users, you might want to raise the

              This  file  shows the number of allocated disk quota entries and
              the number of free disk quota entries.

       /proc/sys/fs/epoll (since Linux 2.6.28)
              echo 100000 > /proc/sys/fs/file-max

              The  kernel constant NR_OPEN imposes an upper limit on the value
              that may be placed in file-max.

              If you  increase  /proc/sys/fs/file-max,  be  sure  to  increase
              /proc/sys/fs/inode-max   to   3-4   times   the   new  value  of
              /proc/sys/fs/file-max, or you will run out of inodes.

              This (read-only)  file  gives  the  number  of  files  presently
              opened.  It contains three numbers: the number of allocated file
              handles; the number of free file handles; and the maximum number
              of file handles.  The kernel allocates file handles dynamically,
              but it doesn't free them again.   If  the  number  of  allocated
              files  is  close  to the maximum, you should consider increasing
              the maximum.  When the number of free  file  handles  is  large,
              you've  encountered a peak in your usage of file handles and you
              probably don't need to increase the maximum.

              This file contains the maximum number of in-memory  inodes.   On
              some (2.4) systems, it may not be present.  This value should be
              3-4 times larger than the value in file-max, since stdin, stdout
              and network sockets also need an inode to handle them.  When you
              regularly run out of inodes, you need to increase this value.

              This file contains the first two values from inode-state.

              This file contains  seven  numbers:  nr_inodes,  nr_free_inodes,
              preshrink,  and  four  dummy values.  nr_inodes is the number of
              inodes the system has allocated.  This can be slightly more than
              inode-max  because Linux allocates them one page full at a time.
              nr_free_inodes represents the number of free inodes.   preshrink
              is  nonzero  when the nr_inodes > inode-max and the system needs
              to prune the inode list instead of allocating more.

       /proc/sys/fs/inotify (since Linux 2.6.13)
              This     directory     contains     files     max_queued_events,
              max_user_instances,  and  max_user_watches,  that can be used to
              limit the amount of kernel memory consumed by the inotify inter-
              face.  For further details, see inotify(7).

              This file specifies the grace period that the kernel grants to a
              process holding a file lease (fcntl(2)) after it has sent a sig-
              nal to that process notifying it that another process is waiting
              to open the file.  If the lease holder does not remove or  down-
              grade  the  lease  within this grace period, the kernel forcibly
              breaks the lease.

              16-bit UIDs and GIDs, although in Linux UIDs  and  GIDs  are  32
              bits.   When  one  of  these file systems is mounted with writes
              enabled, any UID or GID that would exceed 65535 is translated to
              the overflow value before being written to disk.

       /proc/sys/fs/pipe-max-size (since Linux 2.6.35)
              The  value  in  this file defines an upper limit for raising the
              capacity of a pipe using the  fcntl(2)  F_SETPIPE_SZ  operation.
              This  limit applies only to unprivileged processes.  The default
              value for this file is 1,048,576.  The value  assigned  to  this
              file  may  be  rounded  upward,  to  reflect  the value actually
              employed for a  convenient  implementation.   To  determine  the
              rounded-up  value,  display  the  contents  of  this  file after
              assigning a value to it.  The minimum value that can be assigned
              to this file is the system page size.

       /proc/sys/fs/suid_dumpable (since Linux 2.6.13)
              The  value  in  this file determines whether core dump files are
              produced for set-user-ID or  otherwise  protected/tainted  bina-
              ries.  Three different integer values can be specified:

              0 (default)  This  provides  the  traditional (pre-Linux 2.6.13)
              behavior.  A core dump will not be produced for a process  which
              has  changed  credentials  (by calling seteuid(2), setgid(2), or
              similar, or by executing a set-user-ID or set-group-ID  program)
              or whose binary does not have read permission enabled.

              1 ("debug")  All  processes  dump  core when possible.  The core
              dump is owned by the file system user ID of the dumping  process
              and  no security is applied.  This is intended for system debug-
              ging situations only.  Ptrace is unchecked.

              2 ("suidsafe") Any binary which normally  would  not  be  dumped
              (see  "0"  above)  is dumped readable by root only.  This allows
              the user to remove the core dump file but not to read  it.   For
              security  reasons core dumps in this mode will not overwrite one
              another or other files.  This mode is appropriate when  adminis-
              trators  are  attempting  to debug problems in a normal environ-

              This file controls the maximum number of superblocks,  and  thus
              the  maximum number of mounted file systems the kernel can have.
              You only need to increase super-max if you need  to  mount  more
              file systems than the current value in super-max allows you to.

              This file contains the number of file systems currently mounted.

              This  directory  contains  files  controlling  a range of kernel
              parameters, as described below.

              This  file holds the value of the kernel capability bounding set
              (expressed as a signed  decimal  number).   This  set  is  ANDed
              against   the   capabilities   permitted  to  a  process  during
              execve(2).  Starting with Linux 2.6.25, the system-wide capabil-
              ity  bounding  set disappeared, and was replaced by a per-thread
              bounding set; see capabilities(7).

              See core(5).

              See core(5).

              This file controls the handling of Ctrl-Alt-Del  from  the  key-
              board.   When  the  value  in  this  file  is 0, Ctrl-Alt-Del is
              trapped and sent to the init(8) program  to  handle  a  graceful
              restart.   When the value is greater than zero, Linux's reaction
              to a Vulcan Nerve Pinch (tm) will be an immediate reboot,  with-
              out  even syncing its dirty buffers.  Note: when a program (like
              dosemu) has the keyboard in  "raw"  mode,  the  ctrl-alt-del  is
              intercepted by the program before it ever reaches the kernel tty
              layer, and it's up to the program to decide what to do with it.

              This file contains the path for the hotplug policy  agent.   The
              default value in this file is /sbin/hotplug.

       /proc/sys/kernel/domainname and /proc/sys/kernel/hostname
              can  be  used  to  set the NIS/YP domainname and the hostname of
              your box in exactly the same way as the  commands  domainname(1)
              and hostname(1), that is:

                  # echo 'darkstar' > /proc/sys/kernel/hostname
                  # echo 'mydomain' > /proc/sys/kernel/domainname

              has the same effect as

                  # hostname 'darkstar'
                  # domainname 'mydomain'

              Note,  however, that the classic has the host-
              name "darkstar" and DNS (Internet Domain Name Server) domainname
              "", not to be confused with the NIS (Network Information
              Service) or YP (Yellow  Pages)  domainname.   These  two  domain
              names  are  in general different.  For a detailed discussion see
              the hostname(1) man page.

              (PowerPC only) If this file is set to a nonzero value, the  Pow-
              erPC  htab  (see kernel file Documentation/powerpc/ppc_htab.txt)
              is pruned each time the system hits the idle loop.

              This file defines a system-wide  limit  specifying  the  maximum
              number  of  bytes in a single message written on a System V mes-
              sage queue.

              This file defines the system-wide limit on the number of message
              queue  identifiers.   (This  file  is  only present in Linux 2.4

              This file defines a system-wide parameter used to initialize the
              msg_qbytes setting for subsequently created message queues.  The
              msg_qbytes setting specifies the maximum number  of  bytes  that
              may be written to the message queue.

       /proc/sys/kernel/ostype and /proc/sys/kernel/osrelease
              These files give substrings of /proc/version.

       /proc/sys/kernel/overflowgid and /proc/sys/kernel/overflowuid
              These  files  duplicate  the  files /proc/sys/fs/overflowgid and

              This  file  gives  read/write  access  to  the  kernel  variable
              panic_timeout.   If  this  is  zero,  the  kernel will loop on a
              panic; if nonzero it indicates that the kernel should autoreboot
              after  this number of seconds.  When you use the software watch-
              dog device driver, the recommended setting is 60.

       /proc/sys/kernel/panic_on_oops (since Linux 2.5.68)
              This file controls the kernel's behavior when an oops or BUG  is
              encountered.   If this file contains 0, then the system tries to
              continue operation.  If it contains 1, then the system delays  a
              few  seconds  (to give klogd time to record the oops output) and
              then panics.  If the /proc/sys/kernel/panic file is also nonzero
              then the machine will be rebooted.

       /proc/sys/kernel/pid_max (since Linux 2.5.34)
              This  file  specifies the value at which PIDs wrap around (i.e.,
              the value in this file is one greater  than  the  maximum  PID).
              The  default  value  for  this  file, 32768, results in the same
              range of PIDs as on earlier kernels.  On 32-bit platforms, 32768
              is  the  maximum  value for pid_max.  On 64-bit systems, pid_max
              can be set to any value up to 2^22 (PID_MAX_LIMIT, approximately
              4 million).

       /proc/sys/kernel/powersave-nap (PowerPC only)
              This file contains a flag.  If set, Linux-PPC will use the "nap"
              mode of powersaving, otherwise the "doze" mode will be used.

              The four values in this file are console_loglevel,  default_mes-
              sage_loglevel,     minimum_console_level,    and    default_con-
              sole_loglevel.  These values influence  printk()  behavior  when

              This file defines the maximum number of pseudoterminals.

              This  read-only file indicates how many pseudoterminals are cur-
              rently in use.

              This directory contains various parameters controlling the oper-
              ation of the file /dev/random.  See random(4) for further infor-

              This file is documented in the  kernel  source  file  Documenta-

       /proc/sys/kernel/reboot-cmd (Sparc only)
              This  file  seems  to  be a way to give an argument to the SPARC
              ROM/Flash boot loader.  Maybe  to  tell  it  what  to  do  after

              (Only  in  kernels  up to and including 2.6.7; see setrlimit(2))
              This file can be used to tune the maximum number of POSIX  real-
              time (queued) signals that can be outstanding in the system.

              (Only  in  kernels  up to and including 2.6.7.)  This file shows
              the number POSIX real-time signals currently queued.

       /proc/sys/kernel/sem (since Linux 2.4)
              This file contains 4 numbers defining limits for  System  V  IPC
              semaphores.  These fields are, in order:

              SEMMSL  The maximum semaphores per semaphore set.

              SEMMNS  A  system-wide  limit on the number of semaphores in all
                      semaphore sets.

              SEMOPM  The maximum number of operations that may  be  specified
                      in a semop(2) call.

              SEMMNI  A  system-wide  limit on the maximum number of semaphore

              This file shows the size of the generic SCSI device (sg) buffer.
              You  can't  tune it just yet, but you could change it at compile
              time by editing include/scsi/sg.h  and  changing  the  value  of
              SG_BIG_BUFF.   However,  there shouldn't be any reason to change
              this value.

              can be created.

              This file controls the functions allowed to be  invoked  by  the
              SysRq  key.   By default, the file contains 1 meaning that every
              possible SysRq request is allowed  (in  older  kernel  versions,
              SysRq was disabled by default, and you were required to specifi-
              cally enable it at run-time, but this is not the case any more).
              Possible values in this file are:

                 0 - disable sysrq completely
                 1 - enable all functions of sysrq
                >1 - bitmask of allowed sysrq functions, as follows:
                        2 - enable control of console logging level
                        4 - enable control of keyboard (SAK, unraw)
                        8 - enable debugging dumps of processes etc.
                       16 - enable sync command
                       32 - enable remount read-only
                       64  -  enable signalling of processes (term, kill, oom-
                      128 - allow reboot/poweroff
                      256 - allow nicing of all real-time tasks

              This file is only present if the CONFIG_MAGIC_SYSRQ kernel  con-
              figuration  option is enabled.  For further details see the ker-
              nel source file Documentation/sysrq.txt.

              This file contains a string like:

                  #5 Wed Feb 25 21:49:24 MET 1998

              The "#5" means that this is the fifth  kernel  built  from  this
              source base and the date behind it indicates the time the kernel
              was built.

       /proc/sys/kernel/threads-max (since Linux 2.3.11)
              This file specifies the  system-wide  limit  on  the  number  of
              threads (tasks) that can be created on the system.

       /proc/sys/kernel/zero-paged (PowerPC only)
              This  file  contains  a flag.  When enabled (nonzero), Linux-PPC
              will pre-zero pages in  the  idle  loop,  possibly  speeding  up

              This directory contains networking stuff.  Explanations for some
              of the files under this directory can be  found  in  tcp(7)  and

              This  file  defines  a ceiling value for the backlog argument of
              listen(2); see the listen(2) manual page for details.

              Writing to this file causes the kernel  to  drop  clean  caches,
              dentries  and  inodes from memory, causing that memory to become

              To free pagecache, use echo  1  >  /proc/sys/vm/drop_caches;  to
              free dentries and inodes, use echo 2 > /proc/sys/vm/drop_caches;
              to  free  pagecache,  dentries  and  inodes,  use   echo   3   >

              Because this is a nondestructive operation and dirty objects are
              not freeable, the user should run sync(8) first.

       /proc/sys/vm/legacy_va_layout (since Linux 2.6.9)
              If nonzero, this disables the new 32-bit memory-mapping  layout;
              the kernel will use the legacy (2.4) layout for all processes.

       /proc/sys/vm/memory_failure_early_kill (since Linux 2.6.32)
              Control  how  to kill processes when an uncorrected memory error
              (typically a 2-bit error in a memory module) that cannot be han-
              dled  by  the  kernel is detected in the background by hardware.
              In some cases (like the page still having a valid copy on disk),
              the kernel will handle the failure transparently without affect-
              ing any applications.  But if there is no other up-to-date  copy
              of  the data, it will kill processes to prevent any data corrup-
              tions from propagating.

              The file has one of the following values:

              1:  Kill all processes that have  the  corrupted-and-not-reload-
                  able  page  mapped  as  soon  as the corruption is detected.
                  Note this is not supported for a few types  of  pages,  like
                  kernel  internally  allocated  data  or  the swap cache, but
                  works for the majority of user pages.

              0:  Only unmap the corrupted page from all  processes  and  only
                  kill a process who tries to access it.

              The  kill is performed using a SIGBUS signal with si_code set to
              BUS_MCEERR_AO.  Processes can handle this if they want  to;  see
              sigaction(2) for more details.

              This  feature  is  only  active  on architectures/platforms with
              advanced machine check handling  and  depends  on  the  hardware

              Applications  can override the memory_failure_early_kill setting
              individually with the prctl(2) PR_MCE_KILL operation.

              Only present if  the  kernel  was  configured  with  CONFIG_MEM-

       /proc/sys/vm/memory_failure_recovery (since Linux 2.6.32)
              Enable memory failure recovery (when supported by the platform)

              virtual memory size, resident set size, the CPU that the task is
              scheduled   on,   oom_adj   score   (see   the   description  of
              /proc/[pid]/oom_adj), and command  name.   This  is  helpful  to
              determine  why  the  OOM-killer  was invoked and to identify the
              rogue task that caused it.

              If this contains the value zero, this information is suppressed.
              On  very  large  systems  with thousands of tasks, it may not be
              feasible to dump the memory  state  information  for  each  one.
              Such systems should not be forced to incur a performance penalty
              in OOM situations when the information may not be desired.

              If this is set to nonzero, this information  is  shown  whenever
              the OOM-killer actually kills a memory-hogging task.

              The default value is 0.

       /proc/sys/vm/oom_kill_allocating_task (since Linux 2.6.24)
              This enables or disables killing the OOM-triggering task in out-
              of-memory situations.

              If this is set to zero, the OOM-killer  will  scan  through  the
              entire  tasklist  and select a task based on heuristics to kill.
              This normally selects a rogue memory-hogging task that frees  up
              a large amount of memory when killed.

              If  this is set to nonzero, the OOM-killer simply kills the task
              that triggered the out-of-memory condition.  This avoids a  pos-
              sibly expensive tasklist scan.

              If  /proc/sys/vm/panic_on_oom  is  nonzero,  it takes precedence
              over whatever value is  used  in  /proc/sys/vm/oom_kill_allocat-

              The default value is 0.

              This  file  contains  the kernel virtual memory accounting mode.
              Values are:

                     0: heuristic overcommit (this is the default)
                     1: always overcommit, never check
                     2: always check, never overcommit

              In mode 0, calls of mmap(2) with MAP_NORESERVE are not  checked,
              and  the default check is very weak, leading to the risk of get-
              ting a process "OOM-killed".  Under Linux 2.4 any nonzero  value
              implies  mode  1.   In  mode  2 (available since Linux 2.6), the
              total virtual address space on the system is limited  to  (SS  +
              RAM*(r/100)), where SS is the size of the swap space, and RAM is
              the size of the physical memory, and r is the  contents  of  the
              file /proc/sys/vm/overcommit_ratio.

              allocations to certain nodes  using  memory  policies  (mbind(2)
              MPOL_BIND)  or  cpusets (cpuset(7)) and those nodes reach memory
              exhaustion status, one process may be killed by the  OOM-killer.
              No panic occurs in this case: because other nodes' memory may be
              free, this means the system as a whole may not have  reached  an
              out-of-memory situation yet.

              If  this  file  is  set to the value 2, the kernel always panics
              when an out-of-memory condition occurs.

              The default value is 0.  1 and 2 are for failover of clustering.
              Select either according to your policy of failover.

              The value in this file controls how aggressively the kernel will
              swap memory pages.  Higher values increase aggressiveness, lower
              values decrease aggressiveness.  The default value is 60.

       /proc/sysrq-trigger (since Linux 2.4.21)
              Writing  a  character to this file triggers the same SysRq func-
              tion as typing ALT-SysRq-<character>  (see  the  description  of
              /proc/sys/kernel/sysrq).  This file is normally only writable by
              root.  For further details see the kernel source file Documenta-

              Subdirectory  containing  the  pseudo-files  msg,  sem  and shm.
              These files list the System V Interprocess  Communication  (IPC)
              objects  (respectively:  message  queues, semaphores, and shared
              memory) that currently exist on the  system,  providing  similar
              information  to  that  available  via ipcs(1).  These files have
              headers and are formatted (one IPC object  per  line)  for  easy
              understanding.   svipc(7)  provides  further  background  on the
              information shown by these files.

              Subdirectory containing the pseudo-files and subdirectories  for
              tty drivers and line disciplines.

              This  file  contains two numbers: the uptime of the system (sec-
              onds), and the amount of time spent in idle process (seconds).

              This string identifies the kernel version that is currently run-
              ning.   It  includes  the  contents  of /proc/sys/kernel/ostype,
              /proc/sys/kernel/osrelease  and  /proc/sys/kernel/version.   For
            Linux version 1.0.9 (quinlan@phaze) #1 Sat May 14 01:51:54 EDT 1994

       /proc/vmstat (since Linux 2.6)
              This file displays various virtual memory statistics.

       /proc/zoneinfo (since Linux 2.6.13)

       cat(1), dmesg(1), find(1), free(1), ps(1), tr(1), uptime(1), chroot(2),
       mmap(2), readlink(2), syslog(2), slabinfo(5), hier(7), time(7), arp(8),
       hdparm(8), ifconfig(8), init(8),  lsmod(8),  lspci(8),  mount(8),  net-
       stat(8), procinfo(8), route(8)
       The kernel source files: Documentation/filesystems/proc.txt, Documenta-

       This page is part of release 3.35 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at

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