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

NAME
     jail -- imprison current process and future decendants

LIBRARY
     Standard C Library (libc, -lc)

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

     int
     jail(struct jail *jail);

DESCRIPTION
     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.

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
     prison.

     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.

ERRORS
     jail() will fail if:

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

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

SEE ALSO
     chdir(2), chroot(2)

HISTORY
     The jail() function call appeared in FreeBSD 4.0.

AUTHORS
     The jail feature was written by Poul-Henning Kamp for R&D Associates
     ``http://www.rndassociates.com/'' who contributed it to FreeBSD.

FreeBSD 4.10                    April 28, 1999                    FreeBSD 4.10

NAME | LIBRARY | SYNOPSIS | DESCRIPTION | PRISON? | ERRORS | SEE ALSO | HISTORY | AUTHORS

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