Troubleshooting · Lesson 12 of 26 · 8 minutes

Incident disk filling

Use disk and log evidence for storage triage.

Open the lab Course map

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learner@clairos:~ $

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Your objectives

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1
Check disks
Run df -h.
Hint & worked example
Inspect the virtual filesystem capacity report. Real systems can run out of space or inodes independently.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
df -h
```
Remember: Available space is a snapshot, not a guarantee that a later write will succeed.
2
Size logs
Run du -sh /var/log.
Hint & worked example
Estimate usage attributed to files or directories; compare it with filesystem capacity when investigating storage.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
du -sh /var/log
```
Remember: du describes file usage, whereas df describes filesystem capacity.
3
Find rotated logs
Run find /var/log -name .1.
Hint & worked example
Search directory trees by criteria rather than relying on one shallow listing.
The command outcome must match the task, including successful access or the explicitly requested failure.
```
find /var/log -name .1
```
Remember: Quote wildcard patterns so find receives them instead of the shell expanding them first.

Understand the pattern

Junior operators build confidence by gathering evidence before changing systems.

df: Inspect the virtual filesystem capacity report. Real systems can run out of space or inodes independently.
Available space is a snapshot, not a guarantee that a later write will succeed.
du: Estimate usage attributed to files or directories; compare it with filesystem capacity when investigating storage.
du describes file usage, whereas df describes filesystem capacity.
find: Search directory trees by criteria rather than relying on one shallow listing.
Quote wildcard patterns so find receives them instead of the shell expanding them first.

Worked example and expected result

$ df -h

Filesystem      Size  Used Avail Use% Mounted on
lab-root         20G  6.4G   14G  32% /
lab-logs        2.0G  180M  1.9G   9% /var/log

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

$ du -sh /var/log

3K	/var/log

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

$ find /var/log -name .1

/var/log/nginx-access.log.1
/var/log/nginx-error.log.1

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 “Incident disk filling”, which interpretation is safe?A command appearing in history proves it completed successfully.A successful first check guarantees that every dependent service is healthy.du describes file usage, whereas df describes filesystem capacity.

Apply it elsewhere

Before adapting the du workflow from “Incident disk filling” 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: Incident bad deploy Try an incident drill

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