Setting up LXC on Debian squeeze

Andrius Šutas — Sun, 06 Nov 2011 18:46:23 +0000

This is a step-by-step tutorial on how to install LXC on Debian Squeeze (and possibly other versions). I wrote this down as a reminder to myself because I was unable to find one consistent example source that worked for me. I will not talk what LXC is or why is it good, it has been already done in numerous places.

Installation

Installing required packages:

# apt-get install bridge-utils debootstrap

Setting up a bridge interface:

As I already had bridge set up for OpenVPN, so I skipped this step.
For the most basic bridge add following configuration to /etc/network/interfaces:

# Bridge setup
iface br0 inet static
        bridge_ports eth0 eth1
        address 192.168.0.2
        broadcast 192.168.0.255
        netmask 255.255.255.0
        gateway 192.168.0.1

bridge_ports – specify physical interfaces to be added to br0. You should not put any lines to configure the interfaces that will be used by the bridge, as this will be setup automatically by the scripts when bringing the bridge up.

Installing LXC:
Assuming you’re running Debian Stable (squeeze (v6.0) at the time of writing), then the candidate LXC version should be <0.7.3:
```
apt-cache policy lxc | grep -i candidate
```
All versions up to 0.7.3 (see: bug #601422) by default uses debian lenny distribution for the VM containers. If you are ok with that, go directly to “Using lenny for the container”, otherwise, see below “Using squeeze for the container”.
- Using squeeze for the container:
- Using lenny for the container:
After isntalling LXC tools, it is time to set up cgroups:
```
# echo "cgroup /sys/fs/cgroup cgroup defaults 0 0" >> /etc/fstab
# mount cgroup
```
And a quick check to ensure everything is ok so far:
```
# lxc-checkconfig
```
In output you should see everything enabled apart “Cgroup memory controller”. If you want memory control via cgroups then the Kernel recompilation is needed, which is beyond the scope of this tutorial.

Creating your first VM

Creating root filesystem:
Create directory for VM and install Debian base system using lxc template:
```
# mkdir -p /lxc/vm0
# /usr/lib/lxc/templates/lxc-debian -p /lxc/vm0/
```
This will take longer to complete only the first time you run it, as the subsequent template creations will use debootstrap’s cache.
- Error “Failed getting release file”
  If you get this error during first install, simply change mirror in /usr/lib/lxc/templates/lxc-debian file and repeat steps, e.g.:
```
MIRROR=${MIRROR:-ftp://ftp.lt.debian.org/debian/}
```
Configuring VM:
We are nearly done. The last step is to configure our VM container. Edit the file /lxc/vm0/config while taking special attention to parameters:
```
lxc.network.ipv4 = 192.168.0.123/24
lxc.network.hwaddr = 4a:59:43:49:79:bf
lxc.network.link = br0
lxc.network.type = veth
lxc.network.veth.pair = veth_vm0
```
Notes:
1. IP (in lxc.network.ipv4) must end with CIDR notation of subnet. “/24″ means subnet mask of “255.255.255.0″
2. MAC (in lxc.network.hwaddr) address must not be multicast
3. Name of interface (in lxc.network.veth.pair) can be anything, but I prefer convention “veth_VM-NAME”
Do not forget to configure VM’s interface in file /lxc/vm0/rootfs/etc/network/interfaces to something like:
```
auto eth0
iface eth0 inet static
        address 192.168.0.123
        netmask 255.255.255.0
        gateway 192.168.0.1
```
Starting VM:
Now the final step is to power on and start using your VM:
```
lxc-start -n vm0 -f /lxc/vm0/config
```
You will be attached to a VM console where you can login with user root:root. Do not forget to change the root’s password or disable the account altogether!

Other:

Stopping VM:

lxc-stop -n vm0

Attaching to VM’s console:

lxc-console -n vm0

Auto-starting VMs when host starts:
- LXC <0.7.5:
  Create config symlink:
```
# ln -s /lxc/vm0/conf /etc/lxc/vm0.conf
```
  Then edit file /etc/default/lxc and include something like:
```
RUN=yes
CONF_DIR=/etc/lxc
CONTAINERS="vm0"
```
- LXC >=0.7.5:
```
# ln -s /lxc/vm0/config /etc/lxc/auto/vm0.conf
```
Cloning VM:
This can be achieved by simply copying VM’s directory with:
```
# cp -r /lxc/vm0 /lxc/new_vm
```
After that do not forget to change /lxc/new_vm/config and /lxc/new_vm/rootfs/etc/network/interfaces files to reflect new changes of name, IP/MAC address and rootfs location.
Sharing (binding) host’s directory in VM:
In VM’s config include lxc.mount.entry, e.g. for VM running Apache:
```
lxc.mount.entry = /var/www /lxc/vm0/rootfs/var/www none defaults,bind 0 0
```

References

Detexify – LaTeX symbol classifier

Andrius Šutas — Wed, 09 Mar 2011 03:32:33 +0000

Quick post of something useful I found recently:
Anyone who works with LaTeX knows how time-consuming it can be to find a symbol in symbols-a4.pdf that you just can’t memorize. Detexify is an attempt to simplify this search.