The step by step using lsof command to view or check who currently login on SSH server. The step by step article below show the the example using the lsof command on Linux Fedora sever to view and check who currently login on SHH server. Please note that the default setting for SSH server usually listen on port 22, make sure that you edit the port number if you customize the SHH server setting.
To start check SHH server connection, or who is currently login on our Linux Fedora server using SSH connection.. execute command as show on example below.
check SSH connection using port number:
[root@fedora ~]# lsof -i :22
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
sshd 1892 root 3u IPv6 4966 TCP *:ssh (LISTEN)
sshd 1892 root 4u IPv4 4968 TCP *:ssh (LISTEN)
sshd 14382 root 3r IPv4 56404 TCP 172.16.162.125:ssh->172.16.162.60:directvdata (ESTABLISHED)
sshd 14519 root 3r IPv4 59072 TCP 172.16.162.125:ssh->172.16.162.60:wg-netforce (ESTABLISHED)
sshd 14522 fedora 3u IPv4 59072 TCP 172.16.162.125:ssh->172.16.162.60:wg-netforce (ESTABLISHED)
[root@fedora ~]#
or you also can view or check SSH connection using name:
[root@fedora ~]# lsof -i :ssh
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
sshd 1892 root 3u IPv6 4966 TCP *:ssh (LISTEN)
sshd 1892 root 4u IPv4 4968 TCP *:ssh (LISTEN)
sshd 14382 root 3r IPv4 56404 TCP 172.16.162.125:ssh->172.16.162.60:directvdata (ESTABLISHED)
sshd 14519 root 3r IPv4 59072 TCP 172.16.162.125:ssh->172.16.162.60:wg-netforce (ESTABLISHED)
sshd 14522 fedora 3u IPv4 59072 TCP 172.16.162.125:ssh->172.16.162.60:wg-netforce (ESTABLISHED)
[root@fedora ~]#
Troubleshoot:
1. If you cannot execute the lsof command and show "-bash: lsof: command not found" error, as show on example below
[fedora@fedora ~]$ lsof -i :22
-bash: lsof: command not found
[fedora@fedora ~]$
2. You may need to log in as root user or use the su command as show on example below and supply the root user password when ask...
[fedora@fedora ~]$ su - -c "lsof -i :22"
Password:
[fedora@fedora ~]$
3. or
[fedora@fedora ~]$ su - -c "lsof -i :ssh"
Password:
[fedora@fedora ~]$
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