user ssh login troubleshooting issues

Here I am going to keep updating ways to troubleshoot ssh login issues on linux or unix operating systems.  Even though there are several different flavors and types of linux, the basis is typically the same.  I am currently running/testing these commands on a RH 5.x system

SSH Login Records

$ cat /var/log/secure

SSH Login Attempts

$ cat /var/log/auth.log

(some helpful filters)

$ grep sshd.*Failed /var/log/auth.log | less

$ grep sshd.*Did /var/log/auth.log | less

.ssh/authorized_keys

permissions, compare files checksum

Failed Login Attempts

$ grep "authentication failure" /var/log/secure | awk '{ print $13 }' | cut -b7-  | sort | uniq -c

Capture login attempts

$ tcpdump -w xpackets.pcap src 138.35.28.202 and port 22

NOTES:

$ tcpdump -D (shows available interfaces in the event you want to capture only on one interface with -i eth0)

$ tcpdump -r xpackets.pcap (will read the file file you just captured)