Tag: lxc-create

Change the LXC container root folder under CentOS with SELinux

The default LXC container folder in CentOS (all versions – 7,8, Stream 8 and Stream 9) is /var/lib/lxc, which may resides in the root partition. When changing the lxc.rootfs or (the main directory /var/lib/lxc) to another place, the containers may still work without any additional SELinux permissions. Some tools like lxc-attach would definitely stop working with permission errors – lxc_attach_run_shell: 1333 Permission denied – failed to exec shell. This article will show how to use lxc-create and SELinux commands to properly change the LXC container’s rootfs.
For detailed information how to create a LXC container check out – Run LXC CentOS Stream 9 container with bridged network under CentOS Stream 9 or Run LXC Ubuntu 22.04 LTS container with bridged network under CentOS Stream 9.

Create LXC container with not default path

  • Change the rootfs only. To change only the LXC container root filesystem location use “–dir=” lxc-create option: 
    lxc-create --template download -n mycontainer2 --dir=/mnt/storage/servers/mycontainer2 -- --dist centos --release 9-Stream --arch amd64

    It will place the files under /mnt/storage/servers/mycontainer2, but the configuration will still be located in /var/lib/lxc/mycontainer2/.

    [root@srv ~]# ls -altr /var/lib/lxc/mycontainer2/
total 16
drwxr-xr-x. 3 root root 4096 Oct 14 13:42 ..
drwxr-xr-x. 2 root root 4096 Oct 14 13:42 rootfs
-rw-r-----. 1 root root  775 Oct 14 13:42 config
drwxrwx---. 3 root root 4096 Oct 14 13:42 .
[root@srv ~]# ls -altr /var/lib/lxc/mycontainer2/rootfs/
total 8
drwxr-xr-x. 2 root root 4096 Oct 14 13:42 .
drwxrwx---. 3 root root 4096 Oct 14 13:42 ..
[root@srv ~]# ls -altr /mnt/storage/servers/mycontainer2/
total 76
drwxrwxrwt.  2 root root 4096 Aug  9  2021 tmp
drwxr-xr-x.  2 root root 4096 Aug  9  2021 srv
lrwxrwxrwx.  1 root root    8 Aug  9  2021 sbin -> usr/sbin
drwxr-xr-x.  2 root root 4096 Aug  9  2021 opt
drwxr-xr-x.  2 root root 4096 Aug  9  2021 mnt
drwxr-xr-x.  2 root root 4096 Aug  9  2021 media
lrwxrwxrwx.  1 root root    9 Aug  9  2021 lib64 -> usr/lib64
lrwxrwxrwx.  1 root root    7 Aug  9  2021 lib -> usr/lib
drwxr-xr-x.  2 root root 4096 Aug  9  2021 home
dr-xr-xr-x.  2 root root 4096 Aug  9  2021 boot
lrwxrwxrwx.  1 root root    7 Aug  9  2021 bin -> usr/bin
dr-xr-xr-x.  2 root root 4096 Aug  9  2021 afs
dr-xr-xr-x.  2 root root 4096 Oct 14 07:11 sys
dr-xr-xr-x.  2 root root 4096 Oct 14 07:11 proc
drwxr-xr-x. 12 root root 4096 Oct 14 07:11 usr
drwxr-xr-x.  8 root root 4096 Oct 14 07:11 run
drwxr-xr-x. 18 root root 4096 Oct 14 07:11 var
dr-xr-x---.  2 root root 4096 Oct 14 07:12 root
drwxr-xr-x.  2 root root 4096 Oct 14 07:12 selinux
drwxr-xr-x. 19 root root 4096 Oct 14 07:15 .
drwxr-xr-x.  4 root root 4096 Oct 14 13:41 ..
drwxr-xr-x.  3 root root 4096 Oct 14 13:42 dev
drwxr-xr-x. 63 root root 4096 Oct 14 13:42 etc
  • Change the LXC container path – the folder containing the configuration and the container’s root filesystems use “-P” 
    lxc-create -P /mnt/storage/servers/ --template download -n mycontainer -- --dist centos --release 9-Stream --arch amd64

    All the LXC container configuration and root filesystem will be placed under /mnt/storage/servers/[container_name], which in the example above is /mnt/storage/servers/mycontainer

    [root@srv ~]# ls -al /mnt/storage/servers/mycontainer
total 16
drwxrwx---.  3 root root 4096 Oct 14 13:38 .
drwxr-xr-x.  4 root root 4096 Oct 14 13:41 ..
-rw-r-----.  1 root root  780 Oct 14 13:38 config
drwxr-xr-x. 19 root root 4096 Oct 14 07:15 rootfs

It is better to use the “-P” and to change the LXC container location than only the filesystem path. In this case, a good practice is to make a symbolic link in /var/lib/lxc/[container-name] to the new location:

ln -s /mnt/storage/servers/mycontainer /var/lib/lxc/mycontainer

So all LXC tools will continue to work without explicitly adding an option for the new path of this container.

Change the SELinux file context to be container_var_lib_t of the LXC root filesystem

Add the file context container_var_lib_t to the container’s root filesystem path and change the SELinux labels.
First, verify all the needed tools are installed:

dnf install -y policycoreutils-python-utils container-selinux

Then, add a new file context to the path /mnt/storage/servers/mycontainer and run the restorecon to change the SELinux labels to container_var_lib_t

semanage fcontext -a -t container_var_lib_t '/mnt/storage/servers/mycontainer(/.*)?'
restorecon -Rv /mnt/storage/servers/mycontainer

The file context may be shown with:

[root@srv ~]# ls -alZ /mnt/storage/servers/mycontainer
total 16
drwxrwx---.  3 root root unconfined_u:object_r:container_var_lib_t:s0 4096 Oct 14 13:38 .
drwxr-xr-x.  4 root root unconfined_u:object_r:mnt_t:s0               4096 Oct 14 13:41 ..
-rw-r-----.  1 root root unconfined_u:object_r:container_var_lib_t:s0  780 Oct 14 13:38 config
drwxr-xr-x. 19 root root unconfined_u:object_r:container_var_lib_t:s0 4096 Oct 14 07:15 rootfs

Failing to set the proper SELinux labels may result to errors such as lxc_attach_run_shell: 1333 Permission denied – failed to exec shell

Run LXC Ubuntu 22.04 LTS container with bridged network under CentOS Stream 9

In continuation of the previous article Run LXC CentOS Stream 9 container with bridged network under CentOS Stream 9, this time the LXC container will be Ubuntu 22.04 LTS Jammy Jellyfish.
To receive a better understanding why to use LXC or a much detailed information of some steps in this article it is better to visit the previously mention article and the original Run LXC CentOS 8 container with bridged network under CentOS 8.

STEP 1) Install the needed software EPEL repository and the LXC and its dependencies

To install LXC software the EPEL CentOS Stream 9 repository must be installed. At present, the LXC included in CentOS Stream 9 EPEL repository is 4.0.

dnf install -y epel-release
dnf install -y lxc lxc-templates container-selinux
dnf install -y wget tar

lxc-templates uses template “download” to download different Linux distribution images from http://images.linuxcontainers.org/, which now redirects to http://uk.lxd.images.canonical.com/ (an Ubuntu lxd images mirror).
The container-selinux should be installed only if the host, i.e. the CentOS Stream 9 install, is with enabled SELinux. The packages offers additional SELinux rules or for the LXC and LXC tools like lxc-attach and more.

STEP 2) Create a Ubuntu 22.04 LTS with the help of LXC templates

[root@srv ~]# lxc-create --template download -n mycontainer -- --dist centos --release 9-Stream --arch amd64

In addition, there is a “–variant” option along with “--dist” and “--release” to specify which variant to install – default, cloud, desktop or other. There is a variant column in the table on the images’ page mentioned above.
Keep on reading!

Run LXC CentOS Stream 9 container with bridged network under CentOS Stream 9

In continue of the previous article with CentOS 8 – Run LXC CentOS 8 container with bridged network under CentOS 8, here is an updated version with CentOS Stream 9 running LXC container. In this case, the LXC container is CentOS Stream 9, too.
Under CentOS 8, the LXC software is from branch 3.x, but in CentOS Stream 9 the LXC is 4.x and there are some differences in the LXC configuration file.
It’s worth mentioning the differences between docker/podman containers and LXC from the previous article:

  • Multiprocesses.
  • Easy configuration modification. Even hot-plugin supported.
  • Unprivileged Linux containers.
  • Complex network setups. Multiple network interfaces connected to different networks, for example.
  • Live systemd, i.e. systemd or SysV init are booted as usual. Much of the software relies on systemd/udev features and in many cases, it is really hard to run software without a systemd or init process

Here are the steps to boot a CentOS Stream 9 container under CentOS Stream 9 host server:

STEP 1) Install EPEL repository.

EPEL CentOS Stream 9 repository now includes LXC 4.0 software.

dnf install -y epel-release

STEP 2) Install LXC software and start LXC service.

At present, the LXC software version is 4.0.12. The package lxc-templates includes template scripts to create a Linux distribution environment like CentOS, Ubuntu, Debian, Gentoo, ArchLinux, Oracle, Alpine, and many others and it also includes the configuration templates to start these Linux distributions. In fact, lxc-templates now includes a download script to download images from the Internet.

dnf install -y lxc lxc-templates container-selinux
dnf install -y wget tar

The wget and tar are required if LXC templates installation is going to be performed.
There is an additional package for container’s SELinux, which should be installed before starting the LXC service, because some of the SELinux rules may not apply in the system. If the SELinux is disabled the installation of container-selinux package might be skipped.

STEP 3) Create a CentOS Stream 9 container with the help of LXC templates and run it.

Use the lxc-templates to prepare a CentOS Stream 9 container environment. The currently available containers are listed here http://images.linuxcontainers.org/, which now redirects to http://uk.lxd.images.canonical.com/ (an Ubuntu lxd images mirror). Check out the URL and choose the right container. Here the CentOS Stream 9 amd64, i.e. release 9-Stream, is used.

[root@srv ~]# lxc-create --template download -n mycontainer -- --dist centos --release 9-Stream --arch amd64

In addition, there is a “–variant” option along with “--dist” and “--release” to specify which variant to install – default, cloud, desktop or other. There is a variant column in the table on the images’ page mentioned above.
Keep on reading!

Run LXC CentOS 8 container with bridged network under CentOS 8

The LXC container software comes to CentOS 8 with the EPEL 8 repository. LXC is a multiprocesses container, which offers to boot a Linux distribution under container isolation. It is very similar to systemd-nspawn and a bit different from docker containers. LXC containers are used when multiple processes are needed under one container only. In most cases, the LXC container is a fully-featured Linux distribution (systemd or SysV, i.e. init) booted under a Linux container.
There are several major differences between docker/podman containers and LXC:

  • Multiprocesses.
  • Easy configuration modification. Even hot-plugin supported.
  • Unprivileged Linux containers.
  • Complex network setups. Multiple network interfaces connected to different networks, for example.
  • Live systemd, i.e. systemd or SysV init are booted as usual. Much of the software rellies on systemd/udev features and in many cases, it is really hard to run a software without a systemd or init process

Here are the steps to boot a CentOS 8 container under CentOS 8 host server:

STEP 1) Install EPEL repository.

EPEL CentOS 8 repository now includes LXC 3.0 software.

dnf install -y epel-release

STEP 2) Install LXC software and start LXC service.

At present, the LXC software version is 3.0.4. The package lxc-templates includes template scripts to create a Linux distribution environment like CentOS, Ubuntu, Debian, Gentoo, ArchLinux, Oracle, Alpine, and many others and it also includes the configuration templates to start these Linux distributions.

dnf install -y lxc lxc-templates
dnf install -y wget tar

The wget and tar are required if LXC templates installation is going to be performed.

STEP 3) Create a CentOS 8 container with the help of LXC templates and run it.

Use the lxc-templates to prepare a CentOS 8 container environment. The currently available containers are listed here http://images.linuxcontainers.org/. Check out the URL and choose the right container. Here the CentOS 8 amd64 is used.

lxc-create --template download -n mycontainer -- --dist centos --release 8 --arch amd64 --keyserver hkp://keyserver.ubuntu.com

Keep on reading!