ControlPath too long ('[...]@uptermd.upterm.dev:22' >= 104 bytes)

[laverdet]

Hello, this isn't a bug report I just want to document this in case anyone runs into it again. I got this error while trying to use upterm and Google wasn't any help.

ControlPath too long ('[...]@uptermd.upterm.dev:22' >= 104 bytes)

I got the error on multiple machines I own so I was pretty confused. It turns out that like 14 years ago I added this to my .ssh/config file and synced it across my devices:

Host *
  ControlPath ~/.ssh/%l-%r@%h:%p

This directive shares one ssh connection between multiple invocations to ssh to the same host. It's actually pretty nice if you're doing a lot of invocations to scp in multiple terminals. Anyway turns out that there's a maximum length on that control path. Uh so if you get this error message that's what's going on.

[xlambein]

I'm having the same issue, which is a bit annoying because I'd like to keep my ControlPath option in my .ssh/config. I'm annoyed that there's this restriction on OpenSSH, but I'm also curious to know why the upterm usernames are so long 😅

[xlambein]

Well, for now I found a fix to my issue. Instead of using %r in the ControlPath, you can use %C, which is a hash of several values including %r, and it's much shorter.

For example, I use ControlPath ~/.ssh/master-%C@%n:%p.