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# inodes

### In linux files are simple structures that do not contain any metadata:

A file is composed of:

* a file name
* an inode number

Directories are Filename-inode number Pairs **Note:** you can think of Diretories as a table of inode parings

```bash
# to view inode-pairs
ls -i
```

### What does an inode contain?

* The size of the file
* The actual physical location on the hard disk where it is located
* Permissions
* Owner, Group owner
* Access time / Modification time, depending on which is active
* Also contains the reference count (basically how many hardlinks point to this particular inode)

### What happens when you use the `ls -l` command?

ls -l --> needs more info --> stat --> looks up the inode --> retuns to shell processor --> output

This runs in a loop for each file in the directory

### Common inode-related Linux Problems:

* No space but after running `df -h` shows space

**This can be caused by inode exhaustion**

Use: `df -hi` to check, if this is at 100% there are no inodes left

#### Causes:

* This can happen on a system where you have a lot of small files that use up all the inodes\*\*
* Can also be caused by systems with a lot of caches

### How inodes are created in Linux:

Classic Filesystems create all the space that they ever going to have when the filesystem is created

Such as: `EXT`

**Note:** Unless you pass an extra flag during installation to overwrite that

Using a modern filesystem like `ZFS`, inodes are created on demand