Networking · Lesson 3 of 26 · 8 minutes

Lsof network review

Use lsof to map listeners to services.

Open the lab Course map

Mastery 0/3Run itExplain itApply it

learner@clairos:~ $

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Your objectives

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1
Show open sockets
Run lsof -i.
Hint & worked example
Inspect a synthetic association between processes and open files or sockets.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
lsof -i
```
Remember: Combine process and socket evidence rather than assuming a service from its port number.
2
Find nginx pid
Run pgrep nginx.
Hint & worked example
Find simulated process IDs by a name pattern.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
pgrep nginx
```
Remember: Verify a process identity before sending a signal.
3
Find sshd pid
Run pgrep sshd.
Hint & worked example
Find simulated process IDs by a name pattern.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
pgrep sshd
```
Remember: Verify a process identity before sending a signal.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

lsof: Inspect a synthetic association between processes and open files or sockets.
Combine process and socket evidence rather than assuming a service from its port number.
pgrep: Find simulated process IDs by a name pattern.
Verify a process identity before sending a signal.

Worked example and expected result

$ lsof -i

COMMAND PID USER   FD  TYPE NAME
nginx    42 www    6u  IPv4 *:80 (LISTEN)
nginx    42 www    7u  IPv4 *:443 (LISTEN)
sshd     77 root   3u  IPv4 *:22 (LISTEN)

Exit status: 0. The command completed successfully in the training fixture.

$ pgrep nginx

Exit status: 0. The command completed successfully in the training fixture.

$ pgrep sshd

Exit status: 0. The command completed successfully in the training fixture.

Try a variation

Repeat this workflow in the sandbox with a different scratch filename. Keep the system fixtures unchanged and compare the observed output with your expectation before moving on.

Explain it

In “Lsof network review”, which interpretation is safe?A successful first check guarantees that every dependent service is healthy.Verify a process identity before sending a signal.A command appearing in history proves it completed successfully.

Apply it elsewhere

Before adapting the pgrep workflow from “Lsof network review” to another server, what should you do?Confirm the current directory, target identity, permissions, and the installed command behavior first.Paste the training paths unchanged into production.Skip output inspection whenever the command is familiar.

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: SSH config dry run Try an incident drill

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