Containerization with LXC
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Installing LXC

At the time of writing this book, there are two long-term support versions of LXC: 1.0 and 2.0. The userspace tools that they provide have some minor differences in command-line flags and deprecations, which I'll be pointing out as we use them.

Installing LXC on Ubuntu with apt

Let's start by installing LXC 1.0 on Ubuntu 14.04.5 (Trusty Tahr):

  1. Install the main LXC package, tooling, and dependencies: 
    root@ubuntu:~# lsb_release -dc
Description: Ubuntu 14.04.5 LTS
Codename: trusty 
root@ubuntu:~# apt-get -y install -y lxc bridge-utils debootstrap libcap-dev cgroup-bin libpam-systemdbridge-utils
root@ubuntu:~#
  2. The package version that Trusty Tahr provides at this time is 1.0.8: 
    root@ubuntu:~# dpkg --list | grep lxc | awk '{print $2,$3}'
liblxc1 1.0.8-0ubuntu0.3
lxc 1.0.8-0ubuntu0.3
lxc-templates 1.0.8-0ubuntu0.3
python3-lxc 1.0.8-0ubuntu0.3
root@ubuntu:~#

To install LXC 2.0, we'll need the Backports repository:

  1. Add the following two lines in the apt sources file: 
    root@ubuntu:~# vim /etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu trusty-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu trusty-backports main restricted universe multiverse
  2. Resynchronize the package index files from their sources: 
    root@ubuntu:~# apt-get update
  3. Install the main LXC package, tooling, and dependencies: 
    root@ubuntu:~# apt-get -y install -y lxc=2.0.3-0ubuntu1~ubuntu14.04.1 lxc1=2.0.3-0ubuntu1~ubuntu14.04.1 liblxc1=2.0.3-0ubuntu1~ubuntu14.04.1 python3- lxc=2.0.3-0ubuntu1~ubuntu14.04.1 cgroup- lite=1.11~ubuntu14.04.2 lxc-templates=2.0.3-0ubuntu1~ubuntu14.04.1bridge-utils
root@ubuntu:~#
  4. Ensure the package versions are on the 2.x branch, in this case 2.0.3: 
    root@ubuntu:~# dpkg --list | grep lxc | awk '{print $2,$3}'
liblxc1 2.0.3-0ubuntu1~ubuntu14.04.1
lxc2.0.3-0ubuntu1~ubuntu14.04.1
lxc-common 2.0.3-0ubuntu1~ubuntu14.04.1
lxc-templates 2.0.3-0ubuntu1~ubuntu14.04.1
lxc1 2.0.3-0ubuntu1~ubuntu14.04.1
lxcfs 2.0.2-0ubuntu1~ubuntu14.04.1
python3-lxc 2.0.3-0ubuntu1~ubuntu14.04.1
root@ubuntu:~#

Installing LXC on Ubuntu from source

To use the latest version of LXC, you can download the source code from the upstream GitHub repository and compile it:

  1. First, let's install git and clone the repository: 
    root@ubuntu:~# apt-get install git
root@ubuntu:~# cd /usr/src
root@ubuntu:/usr/src# git clone https://github.com/lxc/lxc.git
Cloning into 'lxc'...
remote: Counting objects: 29252, done.
remote: Compressing objects: 100% (156/156), done.
remote: Total 29252 (delta 101), reused 0 (delta 0), pack-reused 29096
Receiving objects: 100% (29252/29252), 11.96 MiB | 12.62 MiB/s, done.
Resolving deltas: 100% (21389/21389), done.
root@ubuntu:/usr/src#
  2. Next, let's install the build tools and various dependencies: 
    root@ubuntu:/usr/src# apt-get install -y dev-utils build-essential aclocal automake pkg-config git bridge-utils libcap-dev libcgmanager-dev cgmanager
root@ubuntu:/usr/src#
  3. Now, generate the configure shell script, which will attempt to guess correct values for different system-dependent variables used during compilation: 
    root@ubuntu:/usr/src# cd lxc
root@ubuntu:/usr/src/lxc#./autogen.sh
  4. The configure script provides options that can be enabled or disabled based on what features you would like to be compiled. To learn what options are available and for a short description of each, run the following: 
    root@ubuntu:/usr/src/lxc# ./configure -help
  5. Its time now to run configure. In this example, I'll enable Linux capabilities and cgmanager, which will manage the cgroups for each container: 
    root@ubuntu:/usr/src/lxc# ./configure --enable-capabilities --enable-cgmanager
...
----------------------------
Environment:
 - compiler: gcc
 - distribution: ubuntu
 - init script type(s): upstart,systemd
 - rpath: no
 - GnuTLS: no
 - Bash integration: yes
Security features:
 - Apparmor: no
 - Linux capabilities: yes
 - seccomp: no
 - SELinux: no
 - cgmanager: yes
Bindings:
 - lua: no
 - python3: no
Documentation:
 - examples: yes
 - API documentation: no
 - user documentation: no
Debugging:
 - tests: no
 - mutex debugging: no
Paths:
Logs in configpath: no
root@ubuntu:/usr/src/lxc#

    From the preceding abbreviated output we can see what options are going to be available after compilation. Notice that we are not enabling any of the security features for now, such as Apparmor.

  6. Next, compile with make: 
    root@ubuntu:/usr/src/lxc# make
  7. Finally, install the binaries, libraries, and templates: 
    root@ubuntu:/usr/src/lxc# make install

    As of this writing, the LXC binaries look for their libraries in a different path than where they were installed. To fix this just copy them to the correct location:

    root@ubuntu:/usr/src/lxc# cp /usr/local/lib/liblxc.so* /usr/lib/x86_64-linux-gnu/
  8. To check the version that was compiled and installed, execute the following code: 
    root@ubuntu:/usr/src/lxc# lxc-create --version
2.0.0
root@ubuntu:/usr/src/lxc#

Installing LXC on CentOS with yum

CentOS 7 currently provides LXC version 1.0.8 in their upstream repositories. The following instructions should work on RHEL 7 and CentOS 7:

  1. Install the main package and distribution templates: 
    root@centos:~# cat /etc/redhat-release
CentOS Linux release 7.2.1511 (Core)
root@centos:~# yum install -y lxc lxc-templates
root@centos:~#
  2. Check the installed package versions: 
    root@centos:~# rpm -qa | grep lxc
lua-lxc-1.0.8-1.el7.x86_64
lxc-templates-1.0.8-1.el7.x86_64
lxc-libs-1.0.8-1.el7.x86_64
lxc-1.0.8-1.el7.x86_64
root@centos:~#

Installing LXC on CentOS from source

To install the latest version of LXC, we need to download it from GitHub and compile it, similar to what we did on Ubuntu:

  1. Install the build utilities, git, and various dependencies: 
    root@centos:# cd /usr/src
root@centos:/usr/src# yum install -y libcap-devel libcgroup bridge-utils git
root@centos:/usr/src# yum groupinstall "Development tools"
root@centos:/usr/src#
  2. Next, clone the repository: 
    root@centos:/usr/src# git clone https://github.com/lxc/lxc.git
root@centos:/usr/src# cd lxc/
root@centos:/usr/src/lxc#
  3. Generate the config file: 
    root@centos:/usr/src/lxc# ./autogen.sh
root@centos:/usr/src#
  4. Prepare the software for compilation: 
    root@centos:/usr/src/lxc# ./configure
...
----------------------------
Environment:
 - compiler: gcc
 - distribution: centos
 - init script type(s): sysvinit
 - rpath: no
 - GnuTLS: no
 - Bash integration: yes
Security features:
 - Apparmor: no
 - Linux capabilities: yes
 - seccomp: no
 - SELinux: no
 - cgmanager: no
Bindings:
 - lua: no
 - python3: no
Documentation:
 - examples: yes
 - API documentation: yes
 - user documentation: no
Debugging:
 - tests: no
 - mutex debugging: no
Paths:
Logs in configpath: no
root@centos:/usr/src/lxc#
  5. Compile and install the binaries, libraries, and distribution templates: 
     root@centos:/usr/src/lxc# make && make install
  6. Copy the libraries to where the binaries are expecting them: 
    root@centos:/usr/src/lxc# cp /usr/local/lib/liblxc.so* /usr/lib64/
  7. Finally, to check the version that was compiled and installed, execute the following code: 
    root@centos:/usr/src/lxc# lxc-create --version
2.0.0
root@centos:/usr/src/lxc#

    CentOS 7 ships with systemd as its init system. To start the LXC service, run the following:

    root@centos:/usr/src/lxc# systemctl start lxc.service
root@centos:/usr/src/lxc# systemctl status lxc.service
 * lxc.service - LXC Container Initialization and Autoboot Code
Loaded: loaded (/usr/lib/systemd/system/lxc.service; disabled; vendor preset: disabled)
Active: active (exited) since Tue 2016-08-30 20:03:58 UTC; 6min ago
Process: 10645 ExecStart=/usr/libexec/lxc/lxc-autostart- helper start (code=exited, status=0/SUCCESS)
Process: 10638 ExecStartPre=/usr/libexec/lxc/lxc-devsetup (code=exited, status=0/SUCCESS)
Main PID: 10645 (code=exited, status=0/SUCCESS)
CGroup: /system.slice/lxc.service
Aug 30 20:03:28 centos systemd[1]: Starting LXC Container Initialization and Autoboot Code...
Aug 30 20:03:28 centos lxc-devsetup[10638]: Creating /dev/.lxc
Aug 30 20:03:28 centos lxc-devsetup[10638]: /dev is devtmpfs
Aug 30 20:03:28 centos lxc-devsetup[10638]: Creating /dev/.lxc/user
Aug 30 20:03:58 centos lxc-autostart-helper[10645]: Starting LXC autoboot containers: [ OK ]
Aug 30 20:03:58 nova systemd[1]: Started LXC Container Initialization and Autoboot Code.
root@centos:/usr/src/lxc#

    To ensure LXC was configured correctly during installation, run the following:

    root@centos:/usr/src/lxc# lxc-checkconfig
Kernel configuration found at /boot/config- 3.10.0-327.28.2.el7.x86_64
--- 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 clone_children flag: enabled
Cgroup device: enabled
Cgroup sched: enabled
Cgroup cpu account: enabled
Cgroup memory controller: enabled
Cgroup cpuset: enabled
--- Misc ---
Veth pair device: enabled
Macvlan: enabled
Vlan: enabled
Bridges: enabled
Advanced netfilter: enabled
CONFIG_NF_NAT_IPV4: enabled
CONFIG_NF_NAT_IPV6: enabled
CONFIG_IP_NF_TARGET_MASQUERADE: enabled
CONFIG_IP6_NF_TARGET_MASQUERADE: enabled
CONFIG_NETFILTER_XT_TARGET_CHECKSUM: enabled
--- Checkpoint/Restore ---
checkpoint restore: enabled
CONFIG_FHANDLE: enabled
CONFIG_EVENTFD: enabled
CONFIG_EPOLL: enabled
CONFIG_UNIX_DIAG: enabled
CONFIG_INET_DIAG: enabled
CONFIG_PACKET_DIAG: enabled
CONFIG_NETLINK_DIAG: enabled
File capabilities: enabled
 Note : Before booting a new kernel, you can check its 
 configuration:
usage : CONFIG=/path/to/config /usr/bin/lxc-checkconfig
root@centos:/usr/src/lxc#

LXC directory installation layout

The following table shows the directory layout of LXC that is created after package and source installation. The directories vary depending on the distribution and installation method:

We will explore most of the directories while building, starting, and terminating LXC containers.

Tip

You can change the default installation path when building LXC from source by passing arguments to the configuration script such as configure --prefix.

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