SSH debugging

SSH debugging procedure

If you can not SSH into your ASL server, and you arent sure why you will need to eliminate what is not causing the problem, to find the cause of the problem. This procedure will eliminate as many variables as possible.

1) Log into the system as the root user and disable all firewall rules with this command:

/sbin/service iptables stop

2) back up the sshd configuration

mv /etc/ssh/sshd_config /etc/ssh/sshd_config.bak

3) re-install the openssh daemon

yum reinstall openssh-server

4) Kill any running sshd daemons

/usr/bin/killall -9 sshd

5) Restart the ssh daemon

/sbin/service sshd start

6) Confirm that the ssh daemon is running from the server by telneting to its port with

telnet localhost 22

7) Confirm from an External system that access to the SSH port on the server is not blocked by a 3rd party device, such as a firewall, note change the IP to the IP of the actual server

telnet 1.2.3.4 22

If step 7 fails, then the problem is with a 3rd party device, blocking access to the server

8) ssh into the system using the root account, note change the IP to the IP of the actual server

ssh root@1.2.3.4 -v