DECK 5 — STORAGE, I/O & TROUBLESHOOTING

Standard Input (stdin)

Input source for a command (usually keyboard)

Standard Output (stdout)

Output of a command (usually screen)

Standard Error (stderr)

Error output of a command

Redirection

Sending output to a file instead of the screen

Pipe (|)

Passing output of one command as input to another

/dev/null

A file that discards all data written to it

tee

A command that outputs to both screen and file

fdisk

Command used to create and manage disk partitions

mkfs

Command used to create a file system on a partition

fstab

A configuration file that defines file systems to mount at boot

df

Command used to display disk space usage

du

Command used to display file or directory sizes

lsblk

Command used to list block storage devices

fsck

Command used to check and repair file systems

resize2fs

Command used to resize ext file systems

Logical Volume Manager (LVM)

A system that allows flexible disk management

Physical Volume (PV)

A physical storage device used by LVM

Volume Group (VG)

A pool of storage made from physical volumes

Logical Volume (LV)

A virtual partition created from a volume group

Troubleshooting

The process of identifying and fixing problems

df -h

Command used to check disk space in human-readable format

du -sh

Command used to find large files or directories

iostat

Command used to monitor disk performance

ioping

Command used to measure disk latency

Quota

A limit on how much storage a user can use

Soft Limit

A warning limit that can be temporarily exceeded

Hard Limit

A strict maximum that cannot be exceeded