Disks, partitions, mounting, fstab, BTRFS, LVM, swap, SMART, USB and LUKS.

Inspect

• Block device tree: lsblk

• With filesystem info: lsblk -f

• Custom columns: lsblk -o NAME,SIZE,FSTYPE,MOUNTPOINT,UUID

• Detailed partition info: sudo fdisk -l

• Filesystem usage: df -h

• Inode usage: df -i

• UUIDs and labels: sudo blkid

• Get one UUID: blkid -s UUID -o value /dev/sda1

• Symlinks by UUID/id/label: ls -l /dev/disk/by-uuid/

Mount / umount

• Mount partition: sudo mount /dev/sdb1 /mnt

• Mount by UUID: sudo mount UUID="xxxx-xxxx" /mnt

• Mount with type: sudo mount -t ext4 /dev/sdb1 /mnt

• Mount read-only: sudo mount -o ro /dev/sdb1 /mnt

• Remount with new opts: sudo mount -o remount,rw /mnt

• Mount ISO file: sudo mount -o loop image.iso /mnt/iso

• Mount tmpfs (RAM): sudo mount -t tmpfs -o size=2G tmpfs /mnt/ramdisk

• Mount NFS: sudo mount -t nfs server:/share /mnt/nfs

• Unmount: sudo umount /mnt

• Lazy unmount (detach when free): sudo umount -l /mnt

• Show mounts: findmnt

• Find who’s holding a mount: fuser -mv /mnt or lsof +D /mnt

fstab

• File: /etc/fstab

• Test entries without rebooting: sudo mount -a

• Reload systemd-generated mounts: sudo systemctl daemon-reload

• Example line:

  UUID=xxxx-xxxx /        ext4 defaults,noatime           0 1
  UUID=yyyy-yyyy /home    ext4 defaults                   0 2
  UUID=zzzz-zzzz /boot    vfat defaults,umask=0077        0 2
  tmpfs          /tmp     tmpfs defaults,noatime,mode=1777 0 0
  

Partitioning

• Interactive (MBR/GPT): sudo fdisk /dev/sdb

• GPT-only: sudo gdisk /dev/sdb

• Scriptable:

  sudo parted /dev/sdb mklabel gpt
  sudo parted /dev/sdb mkpart primary ext4 1MiB 100GiB
  sudo parted /dev/sdb resizepart 2 200GiB
  

Format

• ext4: sudo mkfs.ext4 -L data /dev/sdb1

• BTRFS: sudo mkfs.btrfs -L data /dev/sdb1

• FAT32 (EFI): sudo mkfs.fat -F32 /dev/sdb1

• XFS: sudo mkfs.xfs /dev/sdb1

• Swap: sudo mkswap /dev/sdb2 && sudo swapon /dev/sdb2

BTRFS

• Create + mount with compression:

  sudo mkfs.btrfs -L btrfs-data /dev/sdb1
  sudo mount -o compress=zstd,noatime /dev/sdb1 /mnt/data
  

• Create subvolume: sudo btrfs subvolume create /mnt/data/@home

• List subvolumes: sudo btrfs subvolume list /mnt/data

• Mount subvolume: sudo mount -o subvol=@home /dev/sdb1 /home

• Read-only snapshot (for backups): sudo btrfs subvolume snapshot -r /mnt/data/@ /mnt/data/@snapshots/$(date +%F)

• Filesystem usage: sudo btrfs filesystem usage /mnt/data

• Scrub (verify checksums): sudo btrfs scrub start /mnt/data && sudo btrfs scrub status /mnt/data

• Balance: sudo btrfs balance start /mnt/data

• Defragment: sudo btrfs filesystem defragment -r /mnt/data

LVM

PV → VG → LV.

• Create PV: sudo pvcreate /dev/sdb1

• Create VG: sudo vgcreate myvg /dev/sdb1 /dev/sdc1

• Create LV (fixed size): sudo lvcreate -L 50G -n mylv myvg

• Create LV (rest of VG): sudo lvcreate -l 100%FREE -n mylv myvg

• Format + mount: sudo mkfs.ext4 /dev/myvg/mylv && sudo mount /dev/myvg/mylv /mnt/lvm

• Show: sudo pvs && sudo vgs && sudo lvs

• Grow LV + filesystem: sudo lvextend -L +10G --resizefs /dev/myvg/mylv

• LVM snapshot: sudo lvcreate -L 5G -s -n mysnap /dev/myvg/mylv

• Remove (reverse order):

  sudo lvremove /dev/myvg/mylv
  sudo vgremove myvg
  sudo pvremove /dev/sdb1
  

Swap

• Show: swapon --show or free -h

• File-based 4 GiB swap:

  sudo dd if=/dev/zero of=/swapfile bs=1M count=4096
  sudo chmod 600 /swapfile
  sudo mkswap /swapfile
  sudo swapon /swapfile
  

• Disable: sudo swapoff /swapfile

• Tune swappiness: sudo sysctl vm.swappiness=10 (persist in /etc/sysctl.d/99-swappiness.conf)

SMART

Install smartmontools.

• Drive info + SMART support: sudo smartctl -i /dev/sda

• Enable SMART: sudo smartctl -s on /dev/sda

• Full attributes/error log: sudo smartctl -a /dev/sda

• Quick health (PASSED/FAILED): sudo smartctl -H /dev/sda

• Short self-test: sudo smartctl -t short /dev/sda

• Long self-test: sudo smartctl -t long /dev/sda

• NVMe: sudo smartctl -a /dev/nvme0

• Auto monitoring: sudo systemctl enable --now smartd

Disk usage

• One directory size: du -sh /home/jo

• Top-level breakdown sorted: du -h --max-depth=1 /home/jo | sort -hr

• Largest files: find / -type f -exec du -h {} + 2>/dev/null | sort -rh | head -20

• Interactive: ncdu /home

USB drive (ext4 / regular)

• Mount: sudo mount --mkdir /dev/sda1 /mnt/usbstick

• Unmount: sudo umount /mnt/usbstick

USB drive (FAT/exFAT — preserve ownership)

Without uid/gid, FAT mounts as root-owned:

• Mount with user ownership: sudo mount -o uid=1000,gid=1000,umask=002 /dev/sda1 /mnt/usbstick

LUKS encrypted drive

• Initialize (destructive!): sudo cryptsetup luksFormat --type luks2 /dev/sda1

• Open (maps to /dev/mapper/backup): sudo cryptsetup open /dev/sda1 backup

• Mount opened volume: sudo mount --mkdir /dev/mapper/backup /mnt/backup

• Unmount and close: sudo umount /mnt/backup && sudo cryptsetup close backup

• Inspect headers: sudo cryptsetup luksDump /dev/sda1

borg backup (to encrypted or plain mount)

• Initialize: borg init --encryption=none /mnt/backup/arch_backup

• Create backup:

  sudo borg create --verbose --stats --progress \
    --exclude-from /etc/borg-exclude \
    /mnt/backup/arch_backup::"$(hostname)-$(date +%Y-%m-%d-%H%M%S)" \
    /
  

rsync (e.g. sync music to DAP)

• Dry run first: rsync -avh --info=progress2 --dry-run /mnt/storage/Music/ /mnt/dap/

• For real: rsync -avh --info=progress2 /mnt/storage/Music/ /mnt/dap/