====== Linux Commands ======

Quick summary of useful program in Linux for sysadmin purposes. To get a full description of each one __have a look at their [[https://linux.die.net/man/|man pages]]__, by doing ''man //command//''.

----

====== Files ======

=== plocate ===
Powerful file finder on the whole system, run after ''sudo updatedb''. Need to be explicitly installed.\\

Syntax:\\
''plocate test.txt''

Output:
<code>
/home/admin/test.txt
</code>

----

=== tree ===
Print a folder structure. Need to be explicitly installed.\\

Syntax:\\
''tree /home/admin/TreeFolder/''

Output:
<code>
/home/admin/TreeFolder/
├── SubTreeFolder
│   └── SubTreeFile
└── TreeFile
</code>

----

=== namei ===
Follow a pathname until a terminal point is found. Need to be explicitly installed.\\

Syntax:\\
''namei /home/admin/''

Output:
<code>
f: /home/admin/
 d /
 d home
 d admin
</code>

----

====== Logs ======

=== tail ===
Print last n rows of a file. Useful to save live updates to a logfile by redirecting the output. The following example is capturing all SIP request to analyze them later with [[https://www.wireshark.org/|Wireshark]].\\

Syntax:\\
''tail -f /etc/servicepattern/sipprocessor.log > test.log''

Output:\\
In this example, none.\\
Download the file and open it in Wireshark (or manually).

----

====== Networking ======

=== netstat ===
Let you see running program listening on ports. Many more options in the manpage, use it with ''grep'' to look for a specific port.\\

Syntax:\\
''netstat -tulpn''

Output:
<code>
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp        0      0 0.0.0.0:5355            0.0.0.0:*               LISTEN      345/systemd-resolve 
tcp        0      0 127.0.0.1:25            0.0.0.0:*               LISTEN      699/exim4           
tcp        0      0 0.0.0.0:443             0.0.0.0:*               LISTEN      3247/nginx: master  
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      345/systemd-resolve 
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN      3247/nginx: master  
tcp        0      0 127.0.0.54:53           0.0.0.0:*               LISTEN      345/systemd-resolve 
tcp        0      0 0.0.0.0:22              0.0.0.0:*               LISTEN      62083/sshd: /usr/sb 
tcp6       0      0 :::5355                 :::*                    LISTEN      345/systemd-resolve 
tcp6       0      0 :::5000                 :::*                    LISTEN      3905/node /home/adm 
tcp6       0      0 ::1:25                  :::*                    LISTEN      699/exim4           
tcp6       0      0 :::80                   :::*                    LISTEN      3247/nginx: master  
tcp6       0      0 :::22                   :::*                    LISTEN      62083/sshd: /usr/sb 
udp        0      0 127.0.0.54:53           0.0.0.0:*                           345/systemd-resolve 
</code>


Syntax:\\
''netstat -tulpn | grep 5000''

Output:
<code>
tcp6       0      0 :::5000                 :::*                    LISTEN      3905/node /home/adm
</code>


 --- //[[lorenzo.cesana@becloudsolutions.com|Lorenzo Cesana]] 2026/04/16 09:07//