Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I have set up a tunnel via autossh.

This works:

autossh -M 33201 -N -i myIdFile -R 33101:localhost:22

I would like to run autossh in background. Seems easy using the -f option.

This does not work, however:

autossh -f -M 33201 -N -i myIdFile -R 33101:localhost:22

Autossh runs in the background fine, but the ssh connection seems to fail every time. In /var/syslog I see multiple occurences of:

autossh[3420]: ssh exited with error status 255; restarting ssh

What am I doing wrong? A wild guess is it has something to do with the authentication via key file. How can I debug this (adding -v to the ssh options does not seem to log anywhere).

Edit: I got some ssh logs using the -y option

/usr/bin/ssh[3484]: debug1: Next authentication method: publickey
/usr/bin/ssh[3484]: debug1: Trying private key: /home/myuser/.ssh/id_rsa
/usr/bin/ssh[3484]: debug1: Trying private key: /home/myuser/.ssh/id_dsa
/usr/bin/ssh[3484]: debug1: Trying private key: /home/myuser/.ssh/id_ecdsa
/usr/bin/ssh[3484]: debug1: No more authentication methods to try.
/usr/bin/ssh[3484]: fatal: Permission denied (publickey).
autossh[3469]: ssh exited with error status 255; restarting ssh

So it seems autossh does not accept my identiy file (-i myIdFile) when using the -f option. Why is that?

(autossh 1.4c on Raspian)

share|improve this question
up vote 8 down vote accepted

It seems like when autossh drops to the background (-f option) it is changing the working directory, meaning relative paths do not work any longer. Or more specific: By entering the absolute path of your id file you will probably succeed.

I re-created the scenario by creating a key with no password at a non-default location:

~/$ mkdir test
~/$ cd test
~/test$ ssh-keygen -f test_id_rsa

I simply hit enter twice to generate a key that is not protected by a password.

I copied the new key to my server (which allows password authentication currently):

~/test$ ssh-copy-id -i test_id_rsa user@server

First I confirmed the key was working with regular ssh, then using autossh like you:

~/test$ ssh -i test_id_rsa user@server
~/test$ autossh -M 13000 -N -i test_id_rsa user@server

They both worked fine, so I recreated the problem you had:

~/test$ autossh -f -M 13000 -N -i test_id_rsa user@server

This did not work and the following was written to /var/log/syslog:

autossh[2406]: ssh exited prematurely with status 255; autossh exiting

By changing the path of the keyfile to be absolute, it worked though:

~/test$ autossh -f -M 13000 -N -i /home/user/test/test_id_rsa user@server

No errors in /var/log/syslog.

share|improve this answer
awesome, this works. – henning77 Oct 10 '13 at 12:27
You saved my day! – arno_v Jul 7 '14 at 14:23

Not sure what is going on with the -f but you could also nohup it:

nohup autossh -M 33201 -N -f -i myIdFile -R 33101:localhost:22 &
share|improve this answer
nohup works for me, even without specifying the key file. – valadil Apr 3 '14 at 14:57

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.