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

     jail, jail_attach - imprison current process and future descendants

     Standard C Library (libc, -lc)

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

     jail(struct jail *jail);

     jail_attach(int jid);

     The jail() system call sets up a jail and locks the current process in

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

           struct jail {
                   u_int32_t       version;
                   char            *path;
                   char            *hostname;
                   char            *jailname;
                   unsigned int    ip4s;
                   unsigned int    ip6s;
                   struct in_addr  *ip4;
                   struct in6_addr *ip6;

     ``version'' defines the version of the API in use.  JAIL_API_VERSION is
     defined for the current version.

     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 ``jailname'' pointer is an optional name that can be assigned to the
     jail for example for managment purposes.

     The ``ip4s'' and ``ip6s'' give the numbers of IPv4 and IPv6 addresses
     that will be passed via their respective pointers.

     The ``ip4'' and ``ip6'' pointers can be set to an arrays of IPv4 and IPv6
     addresses to be assigned to the prison, or NULL if none.  IPv4 addresses
     must be in network byte order.

     The jail_attach() system call attaches the current process to an existing
     jail, identified by jid.

     If successful, jail() returns a non-negative integer, termed the jail
     identifier (JID).  It returns -1 on failure, and sets errno to indicate
     the error.

     The jail_attach() function returns the value 0 if successful; otherwise
     the value -1 is returned and the global variable errno is set to indicate
     the error.

     Once a process has been put in a prison, it and its descendants cannot
     escape the prison.

     Inside the prison, the concept of ``superuser'' is very diluted.  In
     general, 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
     cannot be created because they reference shared resources (the device
     drivers in the kernel).  The effective ``securelevel'' for a process is
     the greater of the global ``securelevel'' or, if present, the per-jail

     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.  All
     connections to/from the loopback address ( for IPv4, ::1 for
     IPv6) will be changed to be to/from the primary address of the jail for
     the given address family.

     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
     currently set for the prison for jailed processes.

     The jail() system call 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.

     chdir(2), chroot(2)

     The jail() system call appeared in FreeBSD 4.0.  The jail_attach() system
     call appeared in FreeBSD 5.1.

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

FreeBSD 11.0-PRERELEASE         January 6, 2009        FreeBSD 11.0-PRERELEASE


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