FreeBSD: Jails (1)

Here is the simplest way that I found to create a jail:



- Define a root directory for the jail (e.g. /usr/jails/lighttpd);

mkdir -p /usr/jails/lighttpd
cd /usr/src
make buildworld (OPTIONAL)
make installworld DESTDIR=/usr/jails/lighttpd
make distribution DESTDIR=/usr/jails/lighttpd
mount -t devfs devfs /usr/jails/lighttpd/dev (OPTIONAL)

Note that if the userland has already been rebuilt using make buildworld, then skip this step and install the existing userland into the new jail.

- Copy over the host's /etc/resolv.conf to the jail:

cp /etc/resolv.conf /usr/jails/lighttpd/etc/

- Start the jail for basic configuration (e.g. set root password). By exiting from the shell, the jail will be shut down:

jail -c path=/usr/jails/lighttpd command=bin/sh


- Edit /etc/freebsd-update.conf inside jail in order to avoid errors during FreeBSD update:

from
Components src world kernel
to
Components world kernel

Reason: there are no kernel or kernel sources inside the jail.


- Edit the host's /etc/rc.conf:

#Jails
jail_enable="YES"
jail_list="lighttpd" #(LIST SEPARATED BY SPACE)
ifconfig_vmx3f0_alias0="inet 192.168.0.150/24"


- Create an entry for the jail on the host's /etc/jail.conf:

lighttpd {
  path = /usr/jails/lighttpd;
  mount.devfs;
  devfs_ruleset = 4;
  host.hostname = lighttpd1.wb.lan;
  ip4.addr = 192.168.0.150;
  allow.chflags = 1;
  exec.start = "/bin/sh /etc/rc";
  exec.stop = "/bin/sh /etc/rc.shutdown";
}

At last, restart the the host. The jail will be started automatically in the next boot.
To list the active jails use:

jls

and to access the jail e.g. JID 1:

jexec 1 /bin/tcsh


References:
- https://www.freebsd.org/doc/handbook/jails-build.html
- https://www.freebsd.org/cgi/man.cgi?query=jail&sektion=8&manpath=freebsd-release-ports
- https://srobb.net/freebsdjail.html
- https://www.digitalocean.com/community/questions/freebsd-update-install-command-fails-on-freebsd-10-1-release