Linux Containers (LXC) provide a Free Software virtualization system for computers running GNU/Linux. This is accomplished through kernel level isolation. It allows one to run multiple virtual units simultaneously. Those units, similar to chroots, are sufficiently isolated to guarantee the required security, but utilize available resources efficiently, as they run on the same kernel.
For all related information visit : http://lxc.sourceforge.net/
Full support for LXC (including userspace tools) is available since the Debian 6.0 "Squeeze" release.
Current issues in Debian 7 "Wheezy":
LXC may not provide sufficient isolation at this time, allowing guest systems to compromise the host system under certain conditions
Apparently this is progressing in 3.12/lxc-beta2: https://www.stgraber.org/2014/01/17/lxc-1-0-unprivileged-containers/
lxc-halt times-out (see Start and stop containers below)
You can also read some sub pages :
- Install required packages
aptitude install lxc
- Install optional packages
aptitude install bridge-utils libvirt-bin debootstrap
Prepare the host
Add this line to /etc/fstab
cgroup /sys/fs/cgroup cgroup defaults 0 0
Try to mount it (a reboot solves an eventual "resource busy problem" in any case)
Optional: Enable memory cgroup support (534964) (CONFIG_CGROUP_MEM_RES_CTLR) - Since 2.6.39-bpo60-2 for Squeeze the memory cgroup support is built in, so lxc-checkconfig will give you a green result about this point. At the same time, it is deactivated by default. You need to activate memory cgroup support with a kernel parameter. When using grub2, this can be easily done by adding GRUB_CMDLINE_LINUX="cgroup_enable=memory" in /etc/default/grub and running update-grub2. Same for CONFIG_CGROUP_MEM_RES_CTLR_SWAP - see http://lists.debian.org/debian-kernel/2012/01/msg00804.html .
Check kernel configuration :
# lxc-checkconfig Kernel config /proc/config.gz not found, looking in other places... Found kernel config file /boot/config-2.6.32-5-amd64 --- Namespaces --- Namespaces: enabled Utsname namespace: enabled Ipc namespace: enabled Pid namespace: enabled User namespace: enabled Network namespace: enabled Multiple /dev/pts instances: enabled --- Control groups --- Cgroup: enabled Cgroup namespace: enabled Cgroup device: enabled Cgroup sched: enabled Cgroup cpu account: enabled Cgroup memory controller: missing Cgroup cpuset: enabled --- Misc --- Veth pair device: enabled Macvlan: enabled Vlan: enabled File capabilities: enabled Note : Before booting a new kernel, you can check its configuration usage : CONFIG=/path/to/config /usr/bin/lxc-checkconfig
Here, I've Cgroup memory controller: missing. If you want memory control via cgroups then the Kernel recompilation is needed.
Debian 8 "Jessie"/testing
Same as Debian 7 (see below), though if you want to specify the suite or mirror, use environment variables:
SUITE=wheezy MIRROR=http://ftp.fr.debian.org/debian lxc-create -n myvm -t debian
Debian 7 "Wheezy"
LXC installs correctly on Wheezy (including a working Debian template since 7.4).
lxc-create -n myvm -t debian
which will prompt you on what distribution to install.
Then adapt network configuration in /var/lib/lxc/myvm/config, e.g. to plug it on libvirt's bridge:
lxc.utsname = myvm lxc.network.type = veth lxc.network.flags = up lxc.network.link = virbr0 lxc.network.ipv4 = 0.0.0.0/24 lxc.network.hwaddr = 00:1E:62:CH:NG:ME
Other templates can be downloaded, before 7.4 we recommended the one referenced on the LXC container mailing list:
lxc-create -n myvm -t debian-wheezy # or for a 32-bit container: linux32 lxc-create -n myvm -t debian-wheezy
Debian 6.0 "Squeeze"
- In theory you may use any tool to create a rootfs (debootstrap, multistrap, rootstock) as long as you are sure, that the result will run inside a container.
- For the first time and as an example, use the provided creation script of the lxc package.
cp -a /usr/lib/lxc/templates/lxc-debian /usr/lib/lxc/templates/lxc-squeeze
- (lxc-debian is designed to install lenny, which is no longer accessible from the specified archive.) Edit lxc-squeeze, replacing "lenny" with "squeeze" and "dhcp-client" with "isc-dhcp-client"
lxc-create -n myvm -t squeeze -f /usr/share/doc/lxc/examples/lxc-veth.conf
Here, we use lxc-veth.conf config file
Setup networked containers
Create a bridge on the host (natted/routed), /SimpleBridge
VLAN + bridge setup description, see /VlanNetworking
Use libvirt package for easy network setup (/LibVirtDefaultNetwork)
Start and stop containers
Notes/warnings on starting and stopping containers:
When you connect to a container console, lxc will let you know how to quit it. The first time you log in however, getty will clear the screen, so you'll probably miss this bit of information:
Type <Ctrl+a q> to exit the console, <Ctrl+a Ctrl+a> to enter Ctrl+a itself
If you're using screen and also use the Ctrl+a command prefix, type <Ctrl+a a q> to exit the console.
When you start the container in foreground mode (without -d), there's apparently no way to quit the terminal (<Ctrl+a q> doesn't work). Make sure you start the containers in background mode with -d, unless you need to debug why a container didn't start.
lxc-halt yields telinit: timeout opening/writing control channel /run/initctl - instead, do a 'poweroff' inside the container, (this is bad advice - it powers off the HOST) and finish it off with lxc-stop. Alternative work-around: use lxc.cap.drop = sys_admin in the container config file.
To start a container in the background and attached to the console at any time later run (by default, login/password is root/root):
lxc-start -n myvm -d lxc-console -n myvm
To start a container in foregroup mode and stay attached to the console run (see warning above):
lxc-start -n myvm
To halt a container cleanly by the containers initv-system (see timeout note above):
lxc-halt -n myvm
To stop a container without proper halt inside the container:
lxc-stop -n myvm
To have containers automatically started on booting the host, link their config file in /etc/lxc/auto/:
ln -s /var/lib/lxc/mycontainer/config /etc/lxc/auto/mycontainer
Bind mounts inside the container
By default only the container's filesystem is mounted inside the container (even if on the host, /var/lib/lxc/mycontainer/rootfs has other mount points).
To mount another filesystem in the container, add to /var/lib/lxc/mycontainer/config:
lxc.mount.entry=/path/in/host/mount_point /var/lib/lxc/mycontainer/rootfs/mount_moint none bind 0 0
and restart the container. The mount point will now be visible inside the container as well.
Both paths can be identical if necessary.
LXC on Debian Squeeze (Published on 2010-05-01)
Setting up LXC on Debian squeeze (Published on 06/11/2011)
See also :
http://blog.rot13.org/2010/03/lxc-watchdog_missing_bits_for_openvz_-_linux_containers_migration.html which describes a tool that allows controlling the guest's startup/shutdown through power signals, and also some more setup for consoles.
Known bugs and "got to know issues"
600466 - "Respawning too fast" messages and can't connect to console due to missing tty(1234) nodes in generated container rootfs. Workaround: remove from container's /etc/inittab or start container in interactive mode and mknod -m 660 dev/tty1 c 5 1 for each required tty.
Some bugs that might apply to non-official containers - read the follow-ups for solutions.
- "telinit: /run/initctl: No such file or directory" running lxc-halt?
mknod -m 600 /var/lib/lxc/myvm/rootfs/run/initctl p
and add "sys_admin" to the lxc.cap.drop line in /var/lib/lxc/myvm/config ?