Web Server Rescue

Read-only

Check Filesystem Space with df

Writes are failing and you need to prove which mounted filesystem is full before deleting or moving anything.

Command

df -h

Before you run this

System impact: Read-only. Low when scoped to the shown target.

When not to use it: Do not use it to choose a file to delete. `df` tells you the full mount; `du` or `find` tells you what is using space inside it.

Expected output

A table of filesystems showing size, used space, available space, use percentage, and mount point. The mount point is the key field for the next command.

System impact

Read-only. Nothing changes. The command reports mounted filesystem usage, not individual file or directory size.

Recovery / rollback: no state is changed.

When to use it

Use first in disk triage so cleanup stays inside the filesystem that is actually full.

When not to use it

Do not use it to choose a file to delete. `df` tells you the full mount; `du` or `find` tells you what is using space inside it.

Watch this command run

Command transcript

This sanitized transcript shows the commands and output shape without exposing host details.

demo@lab:~$

$ df -h

Filesystem      Size  Used Avail Use% Mounted on
/dev/vda1        25G   19G  5G  80% /work
tmpfs           982M   12M  970M   2% /run

$ du -xh --max-depth=1 /var 2>/dev/null | sort -h

24M	/var/tmp
180M	/var/cache
1.4G	/var/log
3.8G	/var/lib

View commands shown

These are the commands shown in the sanitized transcript.

Commands shown

df -h
du -xh --max-depth=1 /var 2>/dev/null | sort -h

next steps

Related commands

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Find Large Directories with du

Once you know a filesystem is full, the next question is where.

du -xh --max-depth=1 /var 2>/dev/null | sort -h

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Find Which Folder Is Filling the Disk

The disk was full. The fastest clue was the folder, not the file.

du -sh /var/* 2>/dev/null | sort -h

Hosting Operations Read-only

Check Inodes When Disk Space Looks Fine

Sometimes the disk has free bytes but still cannot create files.

df -ih

Hosting Operations Read-only

Check Bytes and Inodes Before Cleanup

No space left can mean full bytes, full inodes, or both.

df -h /lab/disk-inode-cleanup && df -ih /lab/disk-inode-cleanup