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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

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 following 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

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AUTHORS

This Man page was written by Klavs Klavsen <kl [AT] 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_context.hc?prjstate=1&nodoc=0>;

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