How to clear & clean server root partition safely when you run out of disk space on /dev/mapper/centos-root 100% full

When your /dev/mapper/centos-root partition is critically full, nearing at 98% or more, freeing up space is absolutely necessary in order to avoid bigger server issues. Here’s how you can identify and clean up unnecessary files safely:

1. Analyze Disk Usage

First, check which directories are taking up the most space under /:

du -ahx / | sort -rh | head -n 20

This command lists the top 20 largest files and directories in /.

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2. Check for Logs

Log files can grow large, especially under /var/log. List the largest log files:

du -sh /var/log/*

• Delete old or rotated logs that are no longer needed:

  rm -f /var/log/*.old
  rm -f /var/log/*.gz
  

• Alternatively, truncate large log files:

  > /var/log/large-log-file.log
  

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3. Clear Cache

System caches under /var/cache can consume significant space:

du -sh /var/cache/*

• Clean up package manager cache:

  yum clean all
  

• Remove other caches if necessary:
  bash

  Copy code

  rm -rf /var/cache/*


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4. Temporary Files

Temporary files under /tmp or /var/tmp can also pile up:

• Safely remove old files:
  bash

  Copy code

  rm -rf /tmp/*
rm -rf /var/tmp/*


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5. Remove Unused Kernels

If old kernels are installed and not being used, they can occupy space under /boot. List installed kernels:

Remove old kernels (except the currently active one):

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6. Audit Installed Packages

Check for unnecessary packages that might be installed:

Remove unneeded packages:

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7. Move Files to /home

Since your /home partition has ample space, consider moving non-critical data from / to /home.

For example, move backups or large files:

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8. Reclaim Space from Docker (if applicable)

If you’re using Docker, its files can bloat /var/lib/docker. Clean up unused Docker data:

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9. Find Orphaned Files in /var

Some directories under /var may have orphaned files:

Delete or move large unnecessary files.

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10. Verify Changes

After cleanup, check disk usage again:

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Warnings:

• Double-check before deletion: Always verify files before removing them to avoid deleting critical system files.
• Backup important data: If unsure about a file, move it elsewhere (/home or an external drive) instead of deleting.

If you’re unsure about a specific large file or directory, share its details, and I can guide you further!