Linux commands
Disks and storage#
See what's there (safe)#
| Command | Shows |
|---|---|
lsblk |
All disks and partitions as a tree |
lsblk -o NAME,SIZE,MODEL,FSTYPE,MOUNTPOINTS |
Same, with model, format and where mounted |
lsblk -f |
Formats, labels and UUIDs |
sudo blkid |
UUID of every partition |
findmnt |
Everything mounted, as a tree |
cat /etc/fstab |
What mounts automatically at startup |
Names: nvme0n1 = internal NVMe SSD, sda/sdb = USB or SATA drives, sdb1 = the first partition on sdb.
Free space#
| Command | Shows |
|---|---|
df -h |
Size, used and free space of every mounted disk |
df -h /srv/files |
One disk only |
du -sh FOLDER |
Size of one folder |
sudo du -sh /var/log /srv/* /home/* 2>/dev/null |
Size of the usual big folders |
sudo du -h --max-depth=1 / 2>/dev/null | sort -h |
Biggest top-level folders, sorted |
ncdu /srv |
Interactive explorer of what takes space (sudo apt install ncdu) |
Mount and unmount#
| Command | Does |
|---|---|
sudo mount -a |
Mount everything in /etc/fstab (also tests your fstab for errors) |
sudo umount /srv/backup |
Unmount before unplugging a drive |
mountpoint /srv/backup |
Says whether a drive is really mounted there |
Commands that erase
mkfs, parted, fdisk, wipefs, dd. Only use them as Chapter 15 describes, and only after checking the drive's size and model with lsblk.
Disk health (SMART)#
sudo apt install smartmontools
sudo smartctl -H /dev/sdb # overall health: PASSED or FAILED
sudo smartctl -a /dev/sdb # everything
sudo smartctl -t short /dev/sdb # start a 2-minute self-test
sudo smartctl -l selftest /dev/sdb # read test results afterwards
For the internal NVMe use /dev/nvme0n1. Some USB enclosures don't pass SMART through. If it fails, add -d sat: sudo smartctl -H -d sat /dev/sdb.
What to watch in -a: Reallocated_Sector_Ct, Current_Pending_Sector and Offline_Uncorrectable should be 0. If they grow, replace the drive.
Read speed (safe)#
sudo apt install hdparm
sudo hdparm -t /dev/sdb
USB 2 gives about 30–40 MB/s, USB 3 often 100+ MB/s.