Administering an rpm-ostree based system

At the moment, there are four primary commands to be familiar with on an rpm-ostree based system. Also remember that in a Project Atomic system, the atomic host command (from the Atomic command) is an alias for rpm-ostree. The author tends to use the former on client systems, and the latter on compose servers.

   # atomic host status

Will show you your deployments, in the order in which they will appear in the bootloader. The * shows the currently booted deployment.

   # atomic host upgrade

Will perform a system upgrade, creating a new chroot, and set it as the default for the next boot. You should use systemctl reboot shortly afterwards.

   # atomic host rollback

By default, the atomic upgrade will keep at most two bootable "deployments", though the underlying technology supports more.

# atomic host deploy <version>

This command makes use of the server-side history feature of OSTree. It will search the history of the current branch for a commit with the specified version, and deploy it. This can be used in scripts to ensure consistent updates. For example, if the upstream OS vendor provides an update online, you might not want to deploy it until you've tested it. This helps ensure that when you upgrade, you are getting exactly what you asked for.

Package layering

It is possible to add more packages onto the system that are not part of the commit composed on the server. These additional "layered" packages are persistent across upgrades, rebases, and deploys (contrast with the ostree unlocking mechanism). This allows you to easily enhance the base set of packages on only some machines, or only temporarily (rather than asking to have it part of the server compose and affecting every machine). For example, you may wish to permanently install some diagnostics tools on a test machine.

# rpm-ostree pkg-add <pkg>

Will download the target package, its dependencies, and create a new deployment with those packages installed.

# rpm-ostree pkg-remove <pkg>

Will create a new deployment with the target package removed.

Note that package layering is currently in preview mode and as such may change interface or functionality before being declared stable.

Filesystem layout

The only writable directories are /etc and /var. In particular, /usr has a read-only bind mount at all times. Any data in /var is never touched, and is shared across upgrades.

At upgrade time, the process takes the new default /etc, and adds your changes on top. This means that upgrades will receive new default files in /etc, which is quite a critical feature.

For more information, see OSTree: Adapting.

Operating system changes

  • The RPM database is stored in /usr/share/rpm, and is immutable.
  • A package nss-altfiles is required, and the system password database is stored in /usr/lib/passwd. Similar for the group database. This might change in the future; see this issue.