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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  fea-
       tures 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 fol-

       --print               Display prevailing capability and related state.

       -- [args]             Execute /bin/bash with trailing arguments.

       ==                    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 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 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  per-
                             mitted  capability sets, or the capsh program is operating with CAP_SETPCAP in its effec-
                             tive set.

       --uid=id              Force all uid values to equal id using the setuid(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 pro-
                             cess  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.  Set-
                             ting  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: cap_setpcap.

              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)