Networking · Lesson 8 of 26 · 8 minutes

Hosts file review

Inspect local host mappings.

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learner@clairos:~ $

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Your objectives

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1
Read hosts
Run cat /etc/hosts.
Hint & worked example
Read one or more files to standard output without editing their contents.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
cat /etc/hosts
```
Remember: Reading a source file should precede changing it; avoid printing real secrets.
2
Find host mapping
Run grep clairos /etc/hosts.
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 clairos /etc/hosts
```
Remember: No matches is exit status 1, which is different from a malformed invocation.
3
Inspect hosts file
Run stat /etc/hosts.
Hint & worked example
Inspect a file or directory metadata record, including ownership, permissions, and size.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
stat /etc/hosts
```
Remember: Metadata and file contents answer different questions.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

cat: Read one or more files to standard output without editing their contents.
Reading a source file should precede changing it; avoid printing real secrets.
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.
stat: Inspect a file or directory metadata record, including ownership, permissions, and size.
Metadata and file contents answer different questions.

Worked example and expected result

$ cat /etc/hosts

127.0.0.1 localhost
10.20.30.40 clairos-learn-lab

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

$ grep clairos /etc/hosts

10.20.30.40 clairos-learn-lab

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

$ stat /etc/hosts

Path: /etc/hosts
Type: file
Mode: -rw-r--r--
Owner: root
Group: root
Size: 49 bytes

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 “Hosts file review”, which interpretation is safe?No matches is exit status 1, which is different from a malformed invocation.A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.

Apply it elsewhere

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

Keep the momentum.

Complete the lab, then explain and apply the pattern.

Next: Firewall service match Try an incident drill

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