What could cause the available inode count to run out?

List of main causes:

• Large number of small files: Each file, including empty ones, uses one inode. If a filesystem contains a huge number of very small files, inodes may run out faster than disk space. For example, temporary session files, log entries, web server caches.
• Incorrect application settings: Some applications may create a large number of temporary files or directories and not delete them properly after completion.
• Program errors: Bugs in programs that constantly create and do not clean up files can lead to rapid inode exhaustion.
• DDoS attacks creating numerous files: In rare cases, attacks may be aimed at creating a huge number of small files to exhaust inode resources.
• Filesystem mounting errors: If the filesystem is mounted incorrectly or with wrong options, it can affect inode management.
• Software failure or system hang: In rare cases, improper shutdown of programs or system failure can leave "hanging" files or blocks that occupy inodes.

To check inode usage, you can use the command:

# Check inode usage in the root partition
df -i /

List of partitions and their usage:

# List all filesystems and their inodes
df -i