use a service to start a new, shared, tmux session (and detach)

Question

I'm trying to use systemctl to launch a process in a new, shared, tmux session. I'm pretty sure my tmux command is all set:

• I have the socket path set with a shared group.
• the service is executing under a user that's a member of the group
• I've tested from the CLI and it works; I can attach with another account.

The command looks like this:

tmux -S /tmp/tmux/sharedsesh new-session -s sharedsesh -d "/usr/bin/java server.jar"

However, when I put it in a new systemctl unit, I'm getting an error: "tmux: unknown option -- S". Since this is an uppercase S, I'm wondering if that means it doesn't have access to sockets or something?

Unit file:

[Unit]
After=network.target

[Service]
WorkingDirectory=/srv/workspace
PrivateUsers=true
User=servhost
Group=servhost
ProtectSystem=full
ProtectHome=true
ProtectKernelTunables=true
ProtectKernelModules=true
ProtectControlGroups=true

ExecStart=/usr/bin/tmux -S /tmp/tmux/sharedsesh new-session -s sharedsesh -d "/usr/bin/java server.jar"

I've looked at the security directives under Service, but in the end I'm left with the error. And, I'm still wondering why it doesn't know about the S option - I'm running the same command as when I do it on the console, so why's it unknown?

== Edit =========

Ok, like so often is the case, just after posting I found my issue.

In fact my ExecStart line is just fine - the error was from my subsequent controls, likely the next one: (bad syntax)

ExecReload=/usr/bin/tmux send-keys -S /tmp/tmux/sharedsesh "reload" Enter
                         ^ -S should be here               ^ send-keys here

In my defense, I was getting the error messages from journalctl which did not show line numbers. Also, I didn't expect it because I didn't expect those to run.

Which leads to my next issue: now that I've fixed the syntax, it's clear that the service is stopping immediately after starting (and Stopping timed out. Terminating. error to boot).

I guess my real issue is something wrong in my Unit file? Or does systemd not like the way tmux detaches? Or something else?

Answer 1

It appears the answer is I needed a Type=forking setting in the Service stanza. Next I have to figure out how to let the service manager know that it was stopped intentionally (when the session terminates, the control process thinks it was a crash). But at least the tmux server and session are persisting and I can connect with a different user.