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JAIL(2)			  FreeBSD System Calls Manual		       JAIL(2)

     jail -- Imprison current process and future decendants.

     #include <sys/types.h>
     #include <sys/jail.h>

     jail(struct jail *jail);

     The jail system call sets up a jail and locks the current process in it.

     The argument is a pointer to a structure describing the prison:

	   struct jail {
		   u_int32_t	   version;
		   char		   *path;
		   char		   *hostname;
		   u_int32_t	   ip_number;

     ``version'' defines the version of	the API	in use.	 It should be set to
     zero at this time.

     The ``path'' pointer should be set	to the directory which is to be	the
     root of the prison.

     The ``hostname'' pointer can be set to the	hostname of the	prison.	 This
     can be changed from the inside of the prison.

     The ``ip_number'' can be set to the IP number assigned to the prison.

     Once a process has	been put in a prison, it and its decendants cannot
     escape the	prison.	 It is not possible to add a process to	a preexisting

     Inside the	prison,	the concept of "superuser" is very diluted.  In	gen-
     eral, it can be assumed that nothing can be mangled from inside a prison
     which does	not exist entirely inside that prison.	For instance the
     directory tree below ``path'' can be manipulated all the ways a root can
     normally do it, including ``rm -rf	/*'' but new device special nodes can-
     not be created because they reference shared resources (the device	driv-
     ers in the	kernel).

     All IP activity will be forced to happen to/from the IP number specified,
     which should be an	alias on one of	the network interfaces.

     It	is possible to identify	a process as jailed by examining
     ``/proc/<pid>/status'': it	will show a field near the end of the line,
     either as a single	hyphen for a process at	large, or the hostname cur-
     rently set	for the	prison for jailed processes.

     jail() will fail if:

     [EINVAL]	  The version number of	the argument is	not correct.

     Further Jail() calls chroot(2) internally,	so the it can fail for all the
     same reasons.  Please consult the chroot(2) manual	page for details.

     chdir(2), chroot(2)

     The jail()	function call appeared in FreeBSD 4.0.

     The jail feature was written by Poul-Henning Kamp for R&D Associates
     ``'' who contributed it to FreeBSD.

FreeBSD	4.0			April 28, 1999			   FreeBSD 4.0


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