Part II · Your system

13. Filesystem

1. 13.1The hierarchy in 2 minutes/etc: system-wide settings, as plain text files.
2. 13.2/tmp vs /var/tmp/tmp: short-lived scratch files. Often in RAM (tmpfs) and emptied at every boot.
3. 13.3/proc and /sysNeither is on disk: the kernel makes up their content when you read it.
4. 13.4Links, inodes and "disk full"An inode is a file's record: owner, rights, size, where the data is. The name is stored in the folder, not in the inode.
5. 13.5fstab and mount options/etc/fstab lists what to mount at boot, one line per filesystem: what, where, type, options, then two numbers.
6. 13.6/dev and udev/dev holds device files: /dev/sda (a disk), /dev/ttyUSB0 (a serial adapter), /dev/null. Programs open them like files to talk to drivers.