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 null-separated strings, with a further null byte ('\0') 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).

       /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.

       /proc/[pid]/oom_score (since Linux 2.6.11)
              This file displays the current score that the  kernel  gives  to
              this process for the purpose of selecting a process for the OOM-
              killer.  A higher score means that the process is more likely to
              be  selected by the OOM-killer.  The basis for this score is the
              amount of memory used by the  process,  with  increases  (+)  or
              decreases (-) for factors including:

              * whether  the  process  creates a lot of children using fork(2)

              * whether the process has been running a long time, or has  used
                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

              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.
                          This is visible whether or  not  the  executable  is
                          swapped out.

              state %c    One  character  from  the string "RSDZTW" where R is
                          running, S is sleeping in an interruptible  wait,  D
                          is  waiting in uninterruptible disk sleep, Z is zom-
                          bie, T is traced or stopped (on a signal), and W  is

              ppid %d     The PID of the parent.

              pgrp %d     The process group ID of the process.

              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 t0 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.

              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
                          real-time  scheduling  policy  (policy  below;   see
                          sched_setscheduler(2)), this is the negated schedul-
                          ing priority, minus one; that is, a  number  in  the
                          range -2 to -100, corresponding to real-time priori-
                          ties 1 to 99.  For processes running  under  a  non-
                          real-time  scheduling  policy,  this is the raw nice
                          value (setpriority(2)) as represented in the kernel.
                          The  kernel  stores  nice  values  as numbers in the
                          range 0 (high) to 39  (low),  corresponding  to  the
                          user-visible nice range of -20 to 19.

                          Before  Linux  2.6, this was a scaled value based on
                          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
                          towards  text,  data, or stack space.  This does not
                          include pages which have not been demand-loaded  in,
                          or which are swapped out.

              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.

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

              sigcatch %lu
                          The bitmap of caught signals, displayed as a decimal
                          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.
                          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
                  dt         dirty pages (unused in Linux 2.6)

              Provides   much  of  the  information  in  /proc/[pid]/stat  and
              /proc/[pid]/statm in a format that's easier for humans to parse.
              Here's an example:

                  $ cat /proc/$$/status
                  Name:   bash
                  State:  S (sleeping)
                  Tgid:   3515
                  Pid:    3515
                  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

                stop)", "Z (zombie)", or "X (dead)".

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

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

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

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

              * FDSize: Number of file descriptor slots currently allocated.

              * Groups: Supplementary group list.

              * VmPeak: Peak virtual memory size.

              * VmSize: Virtual memory size.

              * VmLck: Locked memory size.

              * VmHWM: Peak resident set size ("high water mark").

              * 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.

              * 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
              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
              will  be  the  same  as  in the corresponding file in the parent
              /proc/[pid] directory (e.g., in a multithreaded process, all  of
              the  task/[tid]/cwd  files  will  have  the  same  value  as the
              /proc/[pid]/cwd file in the parent directory, since all  of  the
              threads in a process share a working directory).  For attributes
              that are distinct for each thread, the corresponding files under
              task/[tid]  may  have  different values (e.g., various fields in
              each of the task/[tid]/status files may be  different  for  each

              In a multithreaded process, the contents of the /proc/[pid]/task
              directory are not available if the main thread has already  ter-
              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 :

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

       /proc/diskstats (since Linux 2.5.69)
              This file contains disk I/O statistics  for  each  disk  device.
              See the kernel source file Documentation/iostats.txt for further

              This is a list of the registered ISA DMA (direct memory  access)
              channels in use.

              Empty subdirectory.

              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

              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 is a list of currently registered Input-Output port regions
              that are in use.

       /proc/kallsyms (since Linux 2.5.71)
              This  holds  the  kernel exported symbol definitions used by the
              modules(X) tools to dynamically link and bind loadable  modules.
              In  Linux  2.5.47 and earlier, a similar file with slightly dif-
              ferent syntax was named ksyms.

              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

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

              Before kernel 2.4.19, this file was a list of all the file  sys-
              tems  currently mounted on the system.  With the introduction of
              per-process mount namespaces in Linux 2.4.19, this file became a
              link  to  /proc/self/mounts, which lists the mount points of the
              process's own mount namespace.  The format of this file is docu-
              mented in fstab(5).

              Memory  Type  Range Registers.  See the kernel source file Docu-
              mentation/mtrr.txt for details.

              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 pre-programmed 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

              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.

              Holds a dump of the RAW 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  protocol number pair.  "St" is the internal 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 RAW.  The
              "uid"  field  holds  the  effective  UID  of  the creator of the

              This file holds the ASCII data needed for the IP, ICMP, TCP, and
              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

              number of blocks and partition name.

              This is a listing of all PCI devices found  during  kernel  ini-
              tialization and their configuration.

              This  file has been deprecated in favor of a new /proc interface
              for PCI  (/proc/bus/pci).   It  became  optional  in  Linux  2.2
              (available  with CONFIG_PCI_OLD_PROC set at kernel compilation).
              It became once more non-optionally enabled in Linux 2.4.   Next,
              it  was  deprecated  in  Linux  2.6  (still  available with CON-
              FIG_PCI_LEGACY_PROC set), and finally removed  altogether  since
              Linux 2.6.17.

              A directory with the scsi mid-level pseudo-file and various SCSI
              low-level driver directories, which contain a file for each SCSI
              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

              See slabinfo(5) for details.

              kernel/system statistics.   Varies  with  architecture.   Common
              entries include:

              cpu  3357 0 4313 1362393
                     The   amount  of  time,  measured  in  units  of  USER_HZ
                     (1/100ths  of  a  second  on  most   architectures,   use
                     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)
                     Number  of  processes  in  runnable state.  (Linux 2.5.45

              procs_blocked 2
                     Number of processes blocked waiting for I/O to  complete.
                     (Linux 2.5.45 onwards.)

              Swap areas in use.  See also swapon(8).

              This directory (present since 1.3.57) contains a number of files
              and subdirectories corresponding  to  kernel  variables.   These
              variables  can  be  read  and sometimes modified using the /proc
              file  system,  and  the  (deprecated)  sysctl(2)  system   call.
              Presently, there are subdirectories abi, debug, dev, fs, kernel,
              net, proc, rxrpc, sunrpc and vm that each contain more files and

       /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 contains the subdirectories  binfmt_misc,  epoll,  inotify,
              and mqueue, and files dentry-state, dir-notify-enable, dquot-nr,
              file-max,  file-nr,  inode-max,  inode-nr,  inode-state,  lease-
              break-time,     leases-enable,     overflowgid,     overflowuid,
              suid_dumpable, super-max, and super-nr.

              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
              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)
              This directory contains the file max_user_watches, which can  be
              used  to limit the amount of kernel memory consumed by the epoll
              interface.  For further details, see epoll(7).

              This file defines a system-wide limit  on  the  number  of  open
              files  for  all processes.  (See also setrlimit(2), which can be
              used by a process to set the per-process  limit,  RLIMIT_NOFILE,
              on  the  number of files it may open.)  If you get lots of error
              messages about running out of file handles, try increasing  this

              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,

              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.

              This  file  can  be  used  to  enable  or  disable  file  leases
              (fcntl(2))  on  a  system-wide basis.  If this file contains the
              value 0, leases are disabled.  A non-zero value enables leases.

       /proc/sys/fs/mqueue (since Linux 2.6.6)
              This  directory  contains  files   msg_max,   msgsize_max,   and
              queues_max,  controlling  the  resources  used  by POSIX message
              queues.  See mq_overview(7) for details.

       /proc/sys/fs/overflowgid and /proc/sys/fs/overflowuid
              These files allow you to change the value of the fixed  UID  and
              GID.   The  default  is  65534.   Some file systems only support
              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/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.
              quency.  If BSD-style process accounting is enabled these values
              control its behavior.  If free space on file  system  where  the
              log  lives  goes below lowwater percent accounting suspends.  If
              free space gets  above  highwater  percent  accounting  resumes.
              frequency  determines  how often the kernel checks the amount of
              free space (value is in seconds).  Default values are 4,  2  and
              30.   That  is,  suspend accounting if 2% or less space is free;
              resume it if 4% or more  space  is  free;  consider  information
              about amount of free space valid for 30 seconds.

       /proc/sys/kernel/cap-bound (from Linux 2.2 to 2.6.24)
              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
              cache  of  G3  processor  boards.   If 0, the cache is disabled.
              Enabled if non-zero.

              This file contains the path for the kernel module  loader.   The
              default  value  is  /sbin/modprobe.  The file is only present if
              the kernel is built with the CONFIG_KMOD option enabled.  It  is
              described by the kernel source file Documentation/kmod.txt (only
              present in kernel 2.4 and earlier).

              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 non-zero it indicates that the kernel  should  autore-
              boot  after  this  number of seconds.  When you use the software
              watchdog 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  non-
              zero 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
              on the different loglevels.  Messages  with  a  higher  priority
              than  console_loglevel will be printed to the console.  Messages
              without an explicit  priority  will  be  printed  with  priority
              default_message_level.   minimum_console_loglevel is the minimum
              (highest)  value  to  which   console_loglevel   can   be   set.
              default_console_loglevel   is   the   default   value  for  con-

       /proc/sys/kernel/pty (since Linux 2.6.4)
              This directory contains two files relating to the number of Unix
              98 pseudo-terminals (see pts(4)) on the system.

              This file defines the maximum number of pseudo-terminals.

              This read-only file indicates how many pseudo-terminals 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.

              pages of System V shared memory.

              This file can be used to query and set the run-time limit on the
              maximum (System V IPC) shared memory segment size  that  can  be
              created.   Shared memory segments up to 1GB are now supported in
              the kernel.  This value defaults to SHMMAX.

              (available in Linux 2.4 and onwards)  This  file  specifies  the
              system-wide  maximum  number  of System V shared memory segments
              that 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_MAGIG_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 (non-zero), Linux-PPC
              will pre-zero pages in  the  idle  loop,  possibly  speeding  up
              This directory may be empty.

              This directory supports Sun remote procedure  call  for  network
              file system (NFS).  On some systems, it is not present.

              This directory contains files for memory management tuning, buf-
              fer and cache management.

       /proc/sys/vm/drop_caches (since Linux 2.6.16)
              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 non-destructive operation and dirty objects
              are not freeable, the user should run sync(8) first.

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

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

       /proc/sys/vm/oom_dump_tasks (since Linux 2.6.25)
              Enables a system-wide task dump (excluding kernel threads) to be
              produced when the kernel  performs  an  OOM-killing.   The  dump
              includes  the  following  information  for  each  task  (thread,
              process): thread ID, real user ID, thread group ID (process ID),
              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 non-zero, this information is shown whenever
              the OOM-killer actually kills a memory-hogging task.

              The default value is 0.

              If /proc/sys/vm/panic_on_oom is non-zero,  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 non-zero 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.

              See the description of /proc/sys/vm/overcommit_memory.

       /proc/sys/vm/panic_on_oom (since Linux 2.6.18)
              This enables or disables a kernel panic in an out-of-memory sit-

              If this file is set to the value 0, the kernel's OOM-killer will
              kill some rogue process.  Usually, the  OOM-killer  is  able  to
              kill a rogue process and the system will survive.

              If  this  file  is  set to the value 1, then the kernel normally
              panics when out-of-memory happens.  However, if a process limits
              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.

       /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

              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)
              This file display information about memory zones.  This is  use-
              ful for analyzing virtual memory behavior.

       Many strings (i.e., the environment and command line) are in the inter-
       nal format, with sub-fields terminated by null bytes ('\0'), so you may
       find  that  things are more readable if you use od -c or tr "\000" "\n"
       to read them.  Alternatively, echo `cat <file>` works well.

       This manual page is incomplete, possibly inaccurate, and is the kind of
       thing that needs to be updated very often.

       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 3.23 of the Linux man-pages project.  A
       description of the project, and information about reporting  bugs,  can
       be found at

Linux                             2009-09-30                           PROC(5)
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