Server operations · Lesson 9 of 36 · 7 minutes

Ports and processes

Compare simulated listener and process views.

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learner@clairos:~ $

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Your objectives

Hints are always available. Wrong turns never cost XP.

1
Show sockets
Run ss -tulpn.
Hint & worked example
Inspect simulated listening sockets and connection information.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
ss -tulpn
```
Remember: A listening socket is not proof of correct application responses or external reachability.
2
Show processes
Run ps.
Hint & worked example
Inspect a bounded snapshot of simulated processes.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
ps
```
Remember: A process being present does not prove that its service can handle requests.
3
Search listen config
Run grep listen /etc/nginx/sites-available/learn.conf.
Hint & worked example
Select input lines that match a pattern; -i ignores case, -n adds line numbers, and -v inverts selection.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
grep listen /etc/nginx/sites-available/learn.conf
```
Remember: No matches is exit status 1, which is different from a malformed invocation.

Understand the pattern

Open ports are easier to explain when tied to a process.

ss: Inspect simulated listening sockets and connection information.
A listening socket is not proof of correct application responses or external reachability.
ps: Inspect a bounded snapshot of simulated processes.
A process being present does not prove that its service can handle requests.
grep: Select input lines that match a pattern; -i ignores case, -n adds line numbers, and -v inverts selection.
No matches is exit status 1, which is different from a malformed invocation.

Worked example and expected result

$ ss -tulpn

Netid State  Local Address:Port  Process
udp   UNCONN 0.0.0.0:68          lab-dhcp
tcp   LISTEN 0.0.0.0:22          sshd
tcp   LISTEN 0.0.0.0:80          nginx
tcp   LISTEN 0.0.0.0:443         nginx

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

$ ps

PID  USER      COMMAND
1    root      systemd --simulated
42   www-data  nginx: static process
77   root      sshd: listener
108  learner   clairos-learn-terminal
126  root      cron

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

$ grep listen /etc/nginx/sites-available/learn.conf

  listen 443 ssl;

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 “Ports and processes”, which interpretation is safe?A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.A process being present does not prove that its service can handle requests.

Apply it elsewhere

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

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: Resource baseline Try an incident drill

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