A file system defines how data on storage is divided into files and directories, how names and metadata are recorded, and how space is allocated and located. Examples include NTFS, ext4, APFS, and FAT32.
Why it matters
The file system sets practical limits: maximum file size, filename rules, permission model, and crash recovery behavior. It also decides which operating systems can read a drive. A USB stick formatted as FAT32 cannot hold a single file over 4 GB.
Journaling file systems record planned changes first, which reduces corruption after a power loss.
Example
$ df -T /
Filesystem Type Size Used Avail Use% Mounted on
/dev/sda1 ext4 50G 32G 16G 67% /The command shows the file system type and how full it is.
Common mistakes
- Ignoring free space; many systems misbehave when a disk is nearly full.
- Choosing a file system without checking which operating systems must read it.
- Pulling out a drive without safely ejecting it, risking corruption.
Related
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