Tag Archives: HowTo

VNET Jail HowTo

So Dan has been tweeting that there’s no good example to get started with VNET Jails with jail.conf, I thought it’s time to write one.

In this example I’ve used FreeBSD 12.1-RELEASE

root@jail-host:~ # freebsd-version
root@jail-host:~ # uname -a
FreeBSD jail-host 12.1-RELEASE FreeBSD 12.1-RELEASE r354233 GENERIC  amd64
root@jail-host:~ #

First thing first, let’s setup a bridge on our host

root@jail-host:~ # sysrc cloned_interfaces="bridge0"
cloned_interfaces:  -> bridge0
root@jail-host:~ # sysrc ifconfig_bridge0="inet netmask 0xffffff00 descr jails-bridge"
ifconfig_bridge0:  -> inet netmask 0xffffff00 descr jails-bridge

Start the bridge0 interface without restarting the other interfaces

root@jail-host:~ # service netif start bridge0

Good! let’s setup a ZFS dataset for Jails πŸ˜‰

root@jail-host:~ # zfs create -o mountpoint=/usr/local/jails zroot/jails

Good! now let’s fetch the base.txz file. I will be using my closest mirror, you should use yours.

root@jail-host:~ # mkdir /usr/local/jails/.dist-files
root@jail-host:~ # fetch -o /usr/local/jails/.dist-files/FreeBSD-12.1-RELEASE-base.txz http://mirror.yandex.ru/freebsd/releases/amd64/12.1-RELEASE/base.txz


Now, we will extract the base into the jail.

root@jail-host:~ # zfs create zroot/jails/www
root@jail-host:~ # tar xf /usr/local/jails/.dist-files/FreeBSD-12.1-RELEASE-base.txz -C /usr/local/jails/www/

Nicely done! Now let’s setup our /etc/jail.conf πŸ™‚

Here’s my configuration.

# vim: set syntax=sh:
exec.stop  = "/bin/sh /etc/rc.shutdown";

www {
    $id     = "10";
    $ipaddr = "10.0.0.${id}";
    $mask   = "";
    $gw     = "";
    vnet.interface = "epair${id}b";

    exec.prestart   = "ifconfig epair${id} create up";
    exec.prestart  += "ifconfig epair${id}a up descr vnet-${name}";
    exec.prestart  += "ifconfig bridge0 addm epair${id}a up";

    exec.start      = "/sbin/ifconfig lo0 up";
    exec.start     += "/sbin/ifconfig epair${id}b ${ipaddr} netmask ${mask} up";
    exec.start     += "/sbin/route add default ${gw}";
    exec.start     += "/bin/sh /etc/rc";

    exec.prestop    = "ifconfig epair${id}b -vnet ${name}";

    exec.poststop   = "ifconfig bridge0 deletem epair${id}a";
    exec.poststop  += "ifconfig epair${id}a destroy";

    host.hostname = "${name}.jail-host";
    path = "/usr/local/jails/${name}";
    exec.consolelog = "/var/log/jail-${name}.log";

Now let’s start our Jail!

root@jail-host:~ # service jail enable
jail enabled in /etc/rc.conf
root@jail-host:~ # service jail start www
Starting jails: www.
root@jail-host:~ # jls
   JID  IP Address      Hostname                      Path
     1                  www.jail-host                 /usr/local/jails/www

Let’s check the networking πŸ™‚

root@jail-host:~ # ping -c 1
PING ( 56 data bytes
64 bytes from icmp_seq=0 ttl=64 time=0.164 ms

--- ping statistics ---
1 packets transmitted, 1 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.164/0.164/0.164/0.000 ms

We can do the same from the jail.

root@jail-host:~ # jexec www
root@www:/ # ping -c 1
PING ( 56 data bytes
64 bytes from icmp_seq=0 ttl=64 time=0.087 ms

--- ping statistics ---
1 packets transmitted, 1 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 0.087/0.087/0.087/0.000 ms

We can also stop all the jails.

root@jail-host:~ # service jail stop
Stopping jails: www.

Okay! Couple of notes πŸ™‚

You can have jail.conf at /etc/jail.conf or /etc/something.jail.conf. The problem with the latter is that if you have jail_enable="YES" in rc.conf without defining jail_list then it will run only the jails in /etc/jail.conf

There are more ways to configure VNET Jails, either with jib or jng, an example is here.

Ideally, it would be nice to have /etc/jail.d/myjail.conf, and I wrote a patch for that (D24570), if you are a FreeBSD developer, please have a look πŸ™‚

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FreeBSD ZFS on Root Migration

My home server (running this blog) got old, it has only 2G of RAM and a very old hard drive.

I usually like to use laptops as home server, they get the job done! I know I can’t have fancy things like RAID1, but I usually keep my backups on a separate disk/machine anyway.

So, I got my Dell Latitude E5470 next to my 11 years old Dell Inspiron to start the migration process.

Here’s a simple how-to guide for migrating a FreeBSD system from one machine to another.

Snapshotting The Pool

Okay, on the old host let snapshot the pool.

zfs snap -r zroot@migrate

Let’s save that snapshot in a file.

zfs send -R zroot@migrate | gzip > /usr/local/zroot.zfs.gz

This might take a while, grab some coffee πŸ™‚

Now let’s save the ZFS Boot Environment (bootfs) property

# zpool get bootfs zroot
zroot  bootfs    zroot/ROOT/default  local

Perfect! now let’s go to the new host! πŸ™‚

Installing FreeBSD

Well, this is simple πŸ™‚ first, install FreeBSD on the new machine. DON’T forget to use ZFS! πŸ™‚

The reason why we are doing this so the FreeBSD installer will handle all the boot loader installation process. If you know how to do this manually, then be my guest (and blog about it).

“Reset” ZFS

Okay, now let’s “reset” that pool

zpool destroy zroot
zpool create -R /mnt zroot /dev/ada0p3 # please check the partition index thought
zpool export zroot # so we can import again with -N
zpool import -N -R /mnt zroot

Restore Old Snapshot

Here we go.

ssh antranigv@pingvinashen "gzcat /usr/local/zroot.zfs.gz" | zfs receive -v -u -F zroot

Aaand we wait again.

So, check you restored all the datasets with zfs list -r zroot

Set the bootfs property.

zpool set bootfs=zroot/ROOT/default zroot

Fingers Crossed and reboot

well, now it’s the time.

shutdown -r now


Hope this helps πŸ™‚

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Setting route interface in FreeBSD

I usually blog for myself, so I don’t forget stuff when I need them πŸ˜›

I’m usually connected via WiFi to a network, however, FreeBSD’s WiFi drivers are not very… good. I mean they do work and do essential stuff, but it’s slow πŸ™‚ anyways.

That’s why I’m always connected to the network using a wire as well.

The problem that I always encounter and want to solve is to change the default route’s interface after wiring up πŸ™‚

Here’s how you can do that.

# netstat -4rn | grep default
default        UGS       wlan0
# route change default -ifp em0
change net default: gateway fib 0
# netstat -4rn | grep default
default        UGS         em0

and so on…

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