Useful-commands.md

@@ -13,15 +13,21 @@ journalctl -eu systemd-nspawn@xcache [--since ...]
 ```
 
 # container commands
-run a command in a temporary container using the xcache image (as xrootd user)  
+
+get a shell as xrootd user in a new temporary container using the xcache image
 ```bash
-systemd-nspawn --volatile=overlay -M xcache-$(uuidgen) --private-users=655360 -u xrootd -D /var/lib/machines/xcache <command>
+systemd-nspawn --register=no -D /var/lib/machines/xcache /bin/bash
 ```
-get a shell (as xrootd user)  
+
+`/bin/bash` can also be replaced by an arbitrary command to be run. Pass `-u root` to get a root shell inside the container.
+
+To run an image other than `/var/lib/machines/xcache` additional options have to be passed on the command line since it won't read `/etc/systemd/nspawn/xcache.nspawn` then, e.g.
+
 ```bash
-systemd-nspawn --volatile=overlay -M xcache-$(uuidgen) --private-users=655360 -u xrootd -D /var/lib/machines/xcache /bin/bash
+systemd-nspawn --volatile=overlay --register=no --private-users=655360 -u xrootd -D /var/lib/machines/<some-other-image> <some-command>
 ```
-get a shell in a running container (as root, usually not nescessary)
+
+To get a shell in the **running** xcache container (as root, usually not nescessary)
 ```
 nsenter --target=$(machinectl show --property Leader xcache | sed "s/^Leader=//")  --all
 ```