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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 pro‐
       vided. 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 commands.

       ==                    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 cap_from_text(3).

       --drop=cap-list       Remove the listed capabilities from the prevailing bounding set. The
                             capabilities  are  a  comma separated list of capabilities as recog‐
                             nized by the cap_from_name(3) function. Use of this feature requires
                             that  the  capsh program is operating with CAP_SETPCAP in its effec‐
                             tive 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  get‐
                             grouplist(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 setgid(2) system call.

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

       --keep=<0|1>          In a non-pure capability mode, the kernel provides liberal privilege
                             to  the  super-user.  However, 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 argument. 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 deac‐
                             tivated  when an exec() is performed. See --secbits for ways to dis‐
                             able 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



       --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 rep‐
                             resented in this form. For example, the missing capability from this
                             effective set is 0x0100. By running:

                              capsh --decode=0x0100

                             we observe that the missing capability is: cap_setpcap.

       --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 <morgan AT kernel.org>.

       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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