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
                             prevailing bounding set. The capabilites are a
                             comma separated list of capabilities as
                             recognized by the cap_from_name(3) function. Use
                             of this feature requires that the capsh program
                             is operating with CAP_SETPCAP in its effective

       --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
                             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 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
                             effective 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)