Networking · Lesson 7 of 26 · 8 minutes

DNS file review

Inspect resolver configuration as text.

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Your objectives

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1
Read resolver
Run cat /etc/resolv.conf.
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/resolv.conf
```
Remember: Reading a source file should precede changing it; avoid printing real secrets.
2
Find nameserver
Run grep nameserver /etc/resolv.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 nameserver /etc/resolv.conf
```
Remember: No matches is exit status 1, which is different from a malformed invocation.
3
Inspect resolver file
Run stat /etc/resolv.conf.
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/resolv.conf
```
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/resolv.conf

nameserver 192.0.2.53
# fake resolver for training only

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

$ grep nameserver /etc/resolv.conf

nameserver 192.0.2.53

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

$ stat /etc/resolv.conf

Path: /etc/resolv.conf
Type: file
Mode: -rw-r--r--
Owner: root
Group: root
Size: 55 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 “DNS file review”, which interpretation is safe?A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.No matches is exit status 1, which is different from a malformed invocation.

Apply it elsewhere

Before adapting the grep workflow from “DNS file review” 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: Hosts file review Try an incident drill

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