How to show current CoreOS system version using rpm-ostree

In CoreOS, run

sudo rpm-ostree status

and look for the entry with the dot (●) in front of it to see which deployment - i.e. which CoreOS version is currently active. Then, look for Version: in the line below. This serves as the alternative to lsb_release -a which is not available on CoreOS.

Example output:

State: idle
AutomaticUpdatesDriver: Zincati
  DriverState: active; periodically polling for updates (last checked Thu 2022-12-08 03:49:05 UTC)
Deployments:
● fedora:fedora/x86_64/coreos/stable
                  Version: 37.20221106.3.0 (2022-11-28T20:05:48Z)
               BaseCommit: 6278bd1e5f311880a6975307e7ce734076a0b1a37f8a97c875c07037c748ddcc
             GPGSignature: Valid signature by ACB5EE4E831C74BB7C168D27F55AD3FB5323552A
          LayeredPackages: bmon docker-compose htop iotop make tailscale tree wget xe-guest-utilities-latest

  fedora:fedora/x86_64/coreos/stable
                  Version: 36.20221030.3.0 (2022-11-11T15:51:02Z)
               BaseCommit: eab21e5b533407b67b1751ba64d83c809d076edffa1ff002334603bf13655a14
             GPGSignature: Valid signature by 53DED2CB922D8B8D9E63FD18999F7CBF38AB71F4
          LayeredPackages: bmon docker-compose htop iotop make tailscale tree wget xe-guest-utilities-latest

In this example, CoreOS 37.20221106.3.0is active.