chcontext(8) System Administration chcontext(8)
NAME
chcontext - chcontext allocates a new security context and executes a
command in that context.
SYNTAX
chcontext [options] <command arguments>
DESCRIPTION
chcontext allocates a new security context and executes a command in
that context. By default, a new/unused context is allocated
OPTIONS
--cap CAP_NAME
Add a capability from the command. This option may be repeated
several time. See /usr/include/linux/capability.h In general,
this option is used with the --secure option. --secure removes
most critical capabilities and --cap adds specific ones.
--cap !CAP_NAME
Remove a capability from the command. This option may be
repeated several time. See /usr/include/linux/capability.h
--ctx num
Select the context. Only root in context 0 is allowed to select
a specific context. Context number 1 is special. It can see all
processes in any contexts, but can’t kill them though.
--disconnect
Start the command in background and make the process a child of
process 1.
--domainname new_domainname
Set the domainname (NIS) in the new security context. Use
"none" to unset the domainname.
--flag Set one flag in the new or current security context. The follow-
ing flags are supported. The option may be used several time.
lock: The new process is trapped and can’t use
chcontext anymore.
sched: The new process and its children will
share a common execution priority.
nproc: Limit the number of process in the
vserver according to ulimit setting.
Normally, ulimit is a per user thing.
With this flag, it becomes a per vserver
thing.
private: No one can join this security context
once created.
--hostname new_hostname
Set the hostname in the new security context. This is needed
because if you create a less privileged security context, it may
be unable to change its hostname.
--secure
Remove all the capabilities to make a virtual server trustable.
--silent
Do not print the allocated context number.
Information about context is found in /proc/self/status
FILES
/usr/sbin/chcontext
EXAMPLES
# You must be root, running X. # We start an xterm in another security
context /usr/sbin/chcontext xterm &
# We check, there is no xterm running, yet we can # see it. ps ax |
grep xterm
# Are we running in security context 0 # We check the s_context line in
/proc/self/status cat /proc/self/status
# Ok we in security context 0 # Try the security context 1
/usr/sbin/chcontext --ctx 1 ps ax | grep xterm
# Ok, we see the xterm, we try to kill it /usr/sbin/chcontext --ctx 1
killall xterm
# No, security context 1 can see, but can’t kill # let’s find out in
which security context this # xterm is running /usr/sbin/chcontext
--ctx 1 ps ax | grep xterm
# Ok, this is PID XX. We need the security context /usr/sbin/chcontext
--ctx 1 cat /proc/XX/status
# We see the s_context, this is SS. # We want to kill this process
/usr/sbin/chcontext --ctx SS killall xterm
Please contribute some, if you feel it’s important.
AUTHORS
This Man page was written by Klavs Klavsen <kl@vsen.dk> and based upon
the helpful output from the program itself and the documentation on the
Virtual Server site <http://www.solucorp.qc.ca/miscprj/s_con-
text.hc?prjstate=1&nodoc=0>
SEE ALSO
chbind(8) rebootmgr(8) reducecap(8) vps(8) vpstree(8) vrpm(8)
vserver(8) vserver-stat(8) vtop(8)
Klavs Klavsen <kl@vsen.dk> 0.1.0 chcontext(8)
