CAPSH(1)                         User Commands                        CAPSH(1)

       capsh - capability shell wrapper

       capsh [OPTION]...

       Linux  capability  support and use can be explored and constrained with
       this tool. This tool provides a handy  wrapper  for  certain  types  of
       capability  testing  and  environment  creation.  It also provides some
       debugging features useful for summarizing capability state.

       The tool takes a number of optional arguments, acting on  them  in  the
       order they are provided. They are as follows:

       --print               Display prevailing capability and related state.

       -- [args]             Execute  /bin/bash with trailing arguments. Note,
                             you can use -c 'command to execute' for  specific

       ==                    Execute  capsh  again  with  remaining arguments.
                             Useful for testing exec() behavior.

       --caps=cap-set        Set the prevailing process capabilities to  those
                             specified  by  cap-set.  Where cap-set is a text-
                             representation  of  capability   state   as   per

       --drop=cap-list       Remove  the listed capabilities from the prevail-
                             ing bounding set. The capabilities  are  a  comma
                             separated  list  of capabilities as recognized by
                             the cap_from_name(3) function. Use of  this  fea-
                             ture requires that the capsh program is operating
                             with CAP_SETPCAP in its effective set.

       --inh=cap-list        Set the inheritable set of capabilities  for  the
                             current  process  to  equal those provided in the
                             comma separated list. For this action to succeed,
                             the  prevailing  process should already have each
                             of these capabilities in the union of the current
                             inheritable and permitted capability sets, or the
                             capsh program is operating  with  CAP_SETPCAP  in
                             its effective set.

       --user=username       Assume  the  identity of the named user. That is,
                             look up the user's uid and gid  with  getpwuid(3)
                             and  their group memberships with getgrouplist(3)
                             and set them all.

       --uid=id              Force all  uid  values  to  equal  id  using  the
                             setuid(2) system call.

       --gid=<id>            Force  all  gid values to equal id using the set-
                             gid(2) system call.

       --groups=<id-list>    Set the supplementary  groups  to  the  numerical
                             list  provided.  The groups are set with the set-
                             groups(2) system call.

       --keep=<0|1>          In a non-pure capability mode,  the  kernel  pro-
                             vides  liberal  privilege to the super-user. How-
                             ever, it is  normally  the  case  that  when  the
                             super-user  changes uid to some lesser user, then
                             capabilities are dropped. For  these  situations,
                             the  kernel  can permit the process to retain its
                             capabilities after a setuid(2) system call.  This
                             feature is known as keep-caps support. The way to
                             activate it using this script is with this  argu-
                             ment. Setting the value to 1 will cause keep-caps
                             to be active. Setting it to 0  will  cause  keep-
                             caps  to  deactivate  for the current process. In
                             all  cases,  keep-caps  is  deactivated  when  an
                             exec()  is  performed.  See --secbits for ways to
                             disable this feature.

       --secbits=N           XXX - need to document this feature.

       --chroot=path         Execute the chroot(2) system call  with  the  new
                             root-directory (/) equal to path.  This operation
                             requires CAP_SYS_CHROOT to be in effect.



       --decode=N            This is a convenience feature.  If  you  look  at
                             /proc/1/status  there are some capability related
                             fields of the following form:

                              CapInh:  0000000000000000
                              CapPrm:  ffffffffffffffff
                              CapEff:  fffffffffffffeff
                              CapBnd:  ffffffffffffffff

                             This option provides a  quick  way  to  decode  a
                             capability  vector  represented in this form. For
                             example, the missing capability from this  effec-
                             tive set is 0x0100. By running:

                              capsh --decode=0x0100

                             we   observe  that  the  missing  capability  is:

       --supports=xxx        As the  kernel  evolves,  more  capabilities  are
                             added.  This  option  can  be  used to verify the
                             existence of a  capability  on  the  system.  For
                             example,  --supports=cap_syslog  will cause capsh
                             to promptly exit with a status of 1 when  run  on
                             kernel  2.6.27.   However,  when  run  on  kernel
                             2.6.38 it will silently succeed.

              Following successful execution the tool  exits  with  status  0.
              Following an error, the tool immediately exits with status 1.

       Written by Andrew G. Morgan <>.

       Please report bugs to the author.

       libcap(3), getcap(8),setcap(8) and capabilities(7).

libcap 2                          2011-04-24                          CAPSH(1)
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