[005f]

Description

If a custom userdata_template doesn't set user_name, the end of install-runner.sh runs chown -R ":" over /opt/actions-runner and /opt/hostedtoolcache. That changes no owners, but it still visits every file in the tool cache. On a fresh instance the root volume loads lazily from its snapshot, so the walk is slow. On our Ubuntu runners it adds about one to one and a half minutes to each boot. This change skips both chown calls when user_name is empty. When user_name is set, they run as before.

The module's own user-data.sh templates always set user_name, so default setups behave the same.

There is a side effect change: A chown with an empty owner still clears setuid and setgid bits on the files it visits. With this change, those bits stay as they are when user_name is unset. start-runner.sh still changes the owner of /opt/actions-runner to run_as.

Test Plan

• In an ubuntu:24.04 container, I ran the old and new snippets over a tool cache of 1,000 files and counted chown calls with strace.
  • With user_name unset, the old snippet made 1,009 calls. Owners stayed root:root, and a setuid file lost its setuid bit.
  • With user_name unset, the new snippet made 0 calls. Owners stayed root:root, and the setuid bit stayed.
  • With user_name=ubuntu, both snippets made 1,009 calls and left both trees ubuntu:ubuntu.
• shellcheck reported no new findings.
• Runner syslog showed that the "Set file ownership of action runner" step took ~1 minute off run times.

Related Issues

#2302 added user_name to the Ubuntu example so that the tool cache chown works.