Provided by: libcap2-bin_2.32-1ubuntu0.1_amd64 bug


       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:

       --help                Display the list of commands supported by capsh.

       --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
                             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
                             getgrouplist(3)   and   set   them   all   using  cap_setuid(3)  and
                             cap_setgroups(3).    Following   this   command,    the    effective
                             capabilities  will  be cleared, but the permitted set will not be so
                             the running program is still privileged.

       --modes               Lists all of the libcap modes supported by --mode.

       --mode=<mode>         Force the program into a cap_set_mode(3) security mode.  This  is  a
                             set  of securebits and prevailing capability arrangement recommended
                             for its pre-determined security stance.

       --inmode=<mode>       Confirm that the prevailing mode is so named, or exit with a  status

       --uid=id              Force  all  uid  values to equal id using the setuid(2) system call.
                             This argument may require explicit preparation of the effective set.

       --cap-uid=<uid>       use the cap_setuid(3)  function  to  set  the  uid  of  the  current
                             process.  This  performs  all prepations for setting the uid without
                             dropping capabilities in the process.  Following  this  command  the
                             prevailing effective capabilities will be lowered.

       --is-uid=<id>         Exit with status 1 unless the current uid equals <id>.

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

       --is-gid=<id>         Exit with status 1 unless the current gid equals <id>.

       --groups=<gid-list>   Set  the  supplementary  groups  to the numerical list provided. The
                             groups are set with the setgroups(2) system call. See --user  for  a
                             more convenient way of doing this.

       --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
                             program  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           Set  the  security-bits  for  the  program,  this  is  via prctl(2),
                             PR_SET_SECUREBITS API, and the list  of  supported  bits  and  their
                             meaning can be found in the <sys/secbits.h> header file. The program
                             will list these bits via the --print command.

       --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

       --forkfor=sec         This command causes the program to fork a child process for so  many
                             seconds. The child will sleep that long and then exit with status 0.
                             The purpose  of  this  command  is  to  support  exploring  the  way
                             processes  are  killable  in the face of capability changes. See the
                             --killit command. Only one fork can be active at a time.

       --killit=sig          This commands causes a --forkfor  child  to  be  kill(2)d  with  the
                             specified  signal. The command then waits for the child to exit.  If
                             the exit status does not match the signal being used to kill it, the
                             capsh program exits with status 1.

       --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.

       --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.

       --has-p=xxx           Exit with status 1 unless the permitted vector  has  capability  xxx

       --has-ambient         Performs  a  check  to  see  if  the running kernel supports ambient
                             capabilities. If not, the capsh command exits with status 1.

       --has-a=xxx           Exit with status 1 unless the  ambient  vector  has  capability  xxx

       --addamb=xxx          Adds the specificed ambient capability to the running process.

       --delamb=xxx          Removes the specified ambient capability from the running process.

       --noamb               Drops all ambient capabilities from the running process.

              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 via:


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