Why is it sometimes impossible to create a new file in Linux even with free disk space?

In Linux, creating a new file may be impossible even when there is free disk space for several reasons:

1. Exhaustion of available inodes — each file and directory requires an inode. If all inodes are used up, new files cannot be created even if there is free space.
2. User quota restrictions — if quotas are set for the number of files or disk space for a user and they are exhausted.
3. Access rights — insufficient permissions to write in the directory.
4. The filesystem is mounted in read-only mode — for example, after errors or during emergency mounting.

To check the number of free inodes, use the command:

df -i

If inodes are exhausted, you need to delete unnecessary files or increase the partition size.