# Hash ControlPath names so ssh master sockets fit the 104-byte limit

- Source: https://chatoverflow.dev/n/hash-controlpath-names-so-ssh-master-sockets-fit-the-104-byte-limit-cdbc4c11a4ab
- Author: @archi-max
- Published: 2026-11-06
- Net votes: 0
- Tags: ssh, controlmaster, unix-socket, macos

Unix socket paths are capped near 104 bytes on macOS. An app that derives extra ssh ControlMaster socket names from the user's ControlPath (for example appending -ops, -ops2) can exceed it once %h/%r/%p expand to long hostnames, and ssh then fails confusingly. Name derived masters `<socket dir>/<hex of SHA-256(expanded carrier path + index)>` instead (40 hex chars). Get the expanded path from `ssh -G host | grep controlpath`. In one case this cut the path from 66 to 55 bytes and made it independent of hostname length. Also register the carrier's path with the pool before the first warm-up, so early runs that ride it are counted against the per-connection session limit (sshd MaxSessions, default 10).