This Implements the mumbled about "Jail" feature.

This is a seriously beefed up chroot kind of thing.  The process
is jailed along the same lines as a chroot does it, but with
additional tough restrictions imposed on what the superuser can do.

For all I know, it is safe to hand over the root bit inside a
prison to the customer living in that prison, this is what
it was developed for in fact:  "real virtual servers".

Each prison has an ip number associated with it, which all IP
communications will be coerced to use and each prison has its own
hostname.

Needless to say, you need more RAM this way, but the advantage is
that each customer can run their own particular version of apache
and not stomp on the toes of their neighbors.

It generally does what one would expect, but setting up a jail
still takes a little knowledge.

A few notes:

   I have no scripts for setting up a jail, don't ask me for them.

   The IP number should be an alias on one of the interfaces.

   mount a /proc in each jail, it will make ps more useable.

   /proc/<pid>/status tells the hostname of the prison for
   jailed processes.

   Quotas are only sensible if you have a mountpoint per prison.

   There are no privisions for stopping resource-hogging.

   Some "#ifdef INET" and similar may be missing (send patches!)

If somebody wants to take it from here and develop it into
more of a "virtual machine" they should be most welcome!

Tools, comments, patches & documentation most welcome.

Have fun...

Sponsored by:   http://www.rndassociates.com/
Run for almost a year by:       http://www.servetheweb.com/

3 files changed, 68 insertions, 0 deletions

diff --git a/usr.sbin/jail/Makefile b/usr.sbin/jail/Makefile
new file mode 100644
index 0000000..f90553d
--- /dev/null
+++ b/usr.sbin/jail/Makefile
@@ -0,0 +1,4 @@
+PROG=	jail
+MAN8=	jail.8
+
+.include	<bsd.prog.mk>
diff --git a/usr.sbin/jail/jail.8 b/usr.sbin/jail/jail.8
new file mode 100644
index 0000000..e1108fa
--- /dev/null
+++ b/usr.sbin/jail/jail.8
@@ -0,0 +1,32 @@
+.Dd April 28, 1999
+.Dt JAIL 8
+.Os FreeBSD 4.0
+.Sh NAME
+.Nm jail
+.Nd imprison process and decendants.
+.Sh SYNOPSIS
+.Nm jail
+.Ar path
+.Ar hostname
+.Ar ip-number
+.Sh DESCRIPTION
+The
+.Nm
+command imprisons a process and all future decendants.
+.Pp
+Please see the
+.Xr jail 2
+Manual page for further details.
+.Sh SEE ALSO
+.Xr chroot 2 ,
+.Xr jail 2
+.Sh HISTORY
+The
+.Fn jail
+function call appeared in
+.Fx 4.0 .
+.Pp
+The jail feature was written by Poul-Henning Kamp for
+R&D Associates
+.Dq Li http://www.rndassociates.com/
+who contributed it to FreeBSD.
diff --git a/usr.sbin/jail/jail.c b/usr.sbin/jail/jail.c
new file mode 100644
index 0000000..938c50b
--- /dev/null
+++ b/usr.sbin/jail/jail.c
@@ -0,0 +1,32 @@
+#include <stdio.h>
+#include <err.h>
+#include <sys/types.h>
+#include <sys/jail.h>
+#include <netinet/in.h>
+
+int
+main(int argc, char **argv)
+{
+	struct jail j;
+	int i;
+	struct in_addr in;
+
+	if (argc < 5) 
+		errx(1, "Usage: %s path hostname ip command ...\n", argv[0]);
+	i = chdir(argv[1]);
+	if (i)
+		err(1, "chdir %s", argv[1]);
+	j.path = argv[1];
+	j.hostname = argv[2];
+	i = inet_aton(argv[3], &in);
+	if (!i)
+		errx(1, "Couldn't make sense if ip number\n");
+	j.ip_number = in.s_addr;
+	i = jail(&j);
+	if (i)
+		err(1, "Imprisonment failed");
+	i = execv(argv[4], argv + 4);
+	if (i)
+		err(1, "execv(%s)", argv[4]);
+	exit (0);
+}