When encountering the "no space left on device" problem, first check the disk usage, run df -h to see if the partition space is full, then use the du command to locate large files; secondly, check the usage of inode, run df -i to confirm whether the inode is exhausted due to too many small files; then clean useless files, such as apt cache, old kernel, Docker residues, etc.; finally check the deleted but still occupied files, find out and free the space locked by the process through lsof L1, and the problem can usually be solved.

The disk space is full, and it is quite common for Linux system to prompt "no space left on device". This problem may not be that the hard disk is really full of files, or that the inode is used up, or that some hidden system mechanisms are causing trouble. Don’t rush to restart or reinstall the system first, check a few key points first.

1. Check disk usage: df command

First, run df -h to see the space usage of each partition. The output looks like this:

 Filesystem Size Used Avail Use% Mounted on
/dev/sda1 50G 50G 0 100% /

If the Use% of a partition shows 100%, it means that the partition is indeed full. At this time, you can continue to use du command to find large files, such as:

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

This lists the sizes of each folder in the root directory, helping you quickly locate which directory occupies a lot of space.

Common situations include:

• Too much log files (such as /var/log/ ) accumulate
• Cache files (such as /var/cache/apt/ or Docker images)
• Temporary file accumulation uploaded by users

2. Check the usage of inode: df -i

Sometimes there is still disk space, but the system still reports an error, which may be that the inode has been exhausted . run:

 df -i

If the IUse% reaches 100% in the output, it means that your file number has exceeded the limit. This often occurs in:

• Services with a large number of small files (such as mail servers, cache services)
• The program generates countless small logs or temporary files

The solution is to clean unnecessary files. For example, deleting old logs, cleaning caches, and checking whether there are program exceptions to create a large number of files.

3. Delete useless files to free up space

After finding a large directory that takes up space, you can consider deleting some useless content, such as:

• Clean up apt cache (Ubuntu/Debian):

   sudo apt clean

• Delete old kernel (suitable for systems with frequent upgrades)

  You can use dpkg --list | grep linux-image to find out the old version of the kernel and uninstall it.

• Clean up Docker residues:

   docker image prune -a
  docker system prune -a

Note: It is best to confirm which ones can be deleted before operation, and do not delete important data by mistake.

4. Check for deleted but still occupied space

Sometimes you clearly delete the files, but the space is not released because these files are still occupied by a process. You can use the following command to find this type of file:

 lsof L1

If there is an entry similar to /var/log/syslog in the output, and the column LINKS is 0, it means that the file has been deleted, but is still locked by the process. Restarting the corresponding service or system can free up this part of the space.

Basically these are the methods. When encountering "no space left on device", don't panic. Check the disk space first, then check the inode, and then see if you can delete something. Finally, don't forget to check those files that have been deleted but still occupy space. Problems are usually solved.

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