CAPSH(1) User Commands CAPSH(1)

NAME capsh - capability shell wrapper


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 provided. They are as follows:

--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 prevail- ing bounding set. The capabilites are a comma separated list of capabilities as recognized by the cap_from_name(3) function. Use of this fea- ture 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.

--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 pro- vides liberal privilege to the super-user. How- ever, 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 argu- ment. 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 effec- tive set is 0x0100. By running:

capsh --decode=0x0100

we observe that the missing capability is: cap_setpcap.

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 <>.

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)