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CAPSH(1)				  User Commands 				 CAPSH(1)

NAME
       capsh - capability shell wrapper

SYNOPSIS
       capsh [OPTION]...

DESCRIPTION
       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.

OPTIONS
       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
			     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 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
			     effect.

       --forkfor=sec

       --killit=sig

       --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.

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

AUTHOR
       Written by Andrew G. Morgan <morgan@kernel.org>.

REPORTING BUGS
       Please report bugs to the author.

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

libcap 2				    2011-04-24					 CAPSH(1)
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