Packages

Creating a root image

Create a big empty file:

# dd if=/dev/zero of=root_fs bs=1M count=1000

Format it:

# mke2fs -F -j root_fs

Mount it:

# mkdir uml
# mount root_fs -o loop uml
# cd uml

Install base and openssh:

# mkdir -p var/log tmp
# pacman-g2 -Sy base openssh -r ./

Create etc/fstab with the following contents:

none             /proc            proc        defaults         0   0
none             /sys             sysfs       defaults         0   0
devpts           /dev/pts         devpts      gid=5,mode=620   0   0
/dev/ubda        /                ext3        defaults         1   1

Create etc/sysconfig/keymap with the following contents:

keymap=us

Create etc/profile.d/lang.sh with the following contents:

export LANG=en_US
export LC_ALL=$LANG

We want networking, put the followings to etc/sysconfig/network/default:

[eth0]
options = 192.168.0.1
gateway = default gw 192.168.0.254

If you want to use multiple virtual machines, use 192.168.0.2, 192.168.0.3 and so on instead.

Let's copy in the terminal device and change our root:

# cp -a /dev/tty dev/
# chroot ./

Create a regular user:

# adduser

Remove unnecessary services and enable ssh:

# service keymap del
# service time del
# rm /etc/rc.d/rcS.d/S18rc.time
# service sshd add

Remove unnecessary packages:

# pacman-g2 -R gpm kernel

Change /etc/inittab so that ctrl-alt-del will halt (and not reboot the system). Change the line

ca::ctrlaltdel:/sbin/shutdown -t5 -r now

to

ca::ctrlaltdel:/sbin/shutdown -t5 -h now

Exit from the chroot and umount:

# exit
# cd ..
# umount uml

You're ready, let's register it!

Configuration file

You should edit /etc/sysconfig/uml. Each item in the machines array defines a virtual machine. Here is an example:

machines=('ubd0=/home/uml/root_fs_0 eth0=tuntap,,,192.168.0.254 mem=128MB con0=null,fd:1 con=null')

This does the following:

• root fs will be /home/uml/root_fs_0

• the IP of the host will be 192.168.0.254

• allocate 128MB of memory

• disable console input, console output will be stdout (that'll be logged to /var/log)

• disable other consoles (we don't need them, we can use ssh)

Configuring the host network

First you need the tun kernel module:

# modprobe tun
# echo tun >> /etc/sysconfig/module

Second, you need NAT. Let's assume you access the external network via the eth0 interface, then edit /etc/sysconfig/network/default and search the end of the [eth0] section. Just append

post_up = iptables -t nat -A POSTROUTING -j MASQUERADE

to the section. After a

# netconfig restart

NAT will be enabled.

Now you can easily start/stop your machines using the usual service uml start/stop command.