Most common problems could be:
Directory permissions
| directory | permission | permission code |
| /Users/[usename] | 755 | rwxr-xr-x |
| /Users/[usename]/.ssh | 700 | rwx—— |
| /Users/[usename]/.ssh/id_rsa | 600 | rw——- |
Modifications in SSH config files /etc/ssh/sshd_config
How to debug
On the server:
– You could run another SSH process on different port, and monitor console log.
[cpp]
$ sudo /usr/sbin/sshd -d -p 4444
[/cpp]
The client:
– Connect to the newly instantiated SSH process on port 4444 (-p 4444) with -v (verbose) option and monitor the log.
[cpp]
ssh -v -p 4444 tmux@10.0.1.4 -i ~/.ssh/tmux_ssh
[/cpp]
Once you find the issue and fix it, you could restart the SSH server with the following commands:
[cpp]
$ sudo launchctl unload /System/Library/LaunchDaemons/ssh.plist
$ sudo launchctl load /System/Library/LaunchDaemons/ssh.plist
[/cpp]