Storage

System 2026-04-28

This page covers raw disk and block-device management on Shani OS: inspecting drives, partitioning, filesystem operations, SMART health monitoring, and the udisks2 layer used by desktop tools.

For encrypted volumes see LUKS Management. For Btrfs-specific operations (snapshots, subvolumes, scrub) see Btrfs Deep Dive. For backup strategy see Backup & Recovery.

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Inspecting Block Devices

# List all block devices with sizes and mount points
lsblk

# Detailed view including filesystem type and UUID
lsblk -f

# Show all disks with model, size, and type (rotational/SSD/NVMe)
lsblk -d -o NAME,SIZE,ROTA,TYPE,MODEL

# List partition table for a specific disk
sudo fdisk -l /dev/sda
sudo fdisk -l /dev/nvme0n1

# Show disk UUIDs and labels (useful for fstab)
blkid
sudo blkid /dev/sda1

# Detailed hardware info for a disk
sudo hdparm -I /dev/sda          # ATA drives
sudo nvme id-ctrl /dev/nvme0     # NVMe drives

# Show disk serial, firmware, and transport
sudo smartctl -i /dev/sda

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Partitioning

fdisk — Interactive Partitioner (MBR & GPT)

sudo fdisk /dev/sda

Common fdisk commands inside the prompt:

| Key | Action | |-----|--------| | p | Print current partition table | | n | New partition | | d | Delete partition | | t | Change partition type | | g | Create new GPT table | | o | Create new MBR table | | w | Write and exit | | q | Quit without saving |

gdisk — GPT-only Partitioner

sudo gdisk /dev/sda

parted — Scriptable Partitioner

# Print partition table
sudo parted /dev/sda print

# Create a new GPT table (destructive)
sudo parted /dev/sda mklabel gpt

# Create a partition (start and end in MiB/GiB/%)
sudo parted /dev/sda mkpart primary ext4 1MiB 100GiB

# Resize a partition (filesystem must be resized separately)
sudo parted /dev/sda resizepart 1 200GiB

# Non-interactive (scripted)
sudo parted -s /dev/sdb mklabel gpt mkpart primary 1MiB 100%

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Filesystems

Creating Filesystems

# ext4
sudo mkfs.ext4 /dev/sda1
sudo mkfs.ext4 -L "mydata" /dev/sda1    # with label

# Btrfs
sudo mkfs.btrfs /dev/sda1
sudo mkfs.btrfs -L "data" -d single /dev/sda1

# XFS
sudo mkfs.xfs /dev/sda1

# FAT32 (USB drives, EFI)
sudo mkfs.vfat -F32 /dev/sdb1

# exFAT
sudo mkfs.exfat /dev/sdb1

Mounting

# Mount a filesystem
sudo mount /dev/sda1 /mnt

# Mount with options
sudo mount -o noatime,compress=zstd /dev/sda1 /mnt    # Btrfs
sudo mount -o ro /dev/sda1 /mnt                        # Read-only

# Mount by UUID (preferred in scripts)
sudo mount UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx /mnt

# Mount an ISO image
sudo mount -o loop image.iso /mnt

# Unmount
sudo umount /mnt

# Lazy unmount (detaches when no longer busy)
sudo umount -l /mnt

# Show all currently mounted filesystems
mount | column -t
findmnt
findmnt --real    # physical mounts only

Checking and Repairing

# ext4 — must be unmounted first
sudo e2fsck -f /dev/sda1

# Btrfs — can be run on a mounted filesystem (read-only check)
sudo btrfs check /dev/sda1
sudo btrfs scrub start /          # Online scrub (finds and fixes errors)
sudo btrfs scrub status /

# XFS — must be unmounted
sudo xfs_repair /dev/sda1

# FAT/exFAT
sudo fsck.vfat /dev/sdb1

Resizing

# ext4 — grow (filesystem must be mounted or unmounted)
sudo resize2fs /dev/sda1           # fill the partition
sudo resize2fs /dev/sda1 50G       # specific size

# Btrfs — grow or shrink while mounted
sudo btrfs filesystem resize +20G /mountpoint
sudo btrfs filesystem resize max /mountpoint   # fill partition

# XFS — grow only, must be mounted
sudo xfs_growfs /mountpoint

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/etc/fstab — Persistent Mounts

Entries in /etc/fstab are captured by the /etc overlay and persist across OS updates.

# <device>                                <mountpoint>  <type>   <options>                    <dump> <pass>
UUID=aaaa-bbbb-cccc                       /data         btrfs    defaults,noatime,compress=zstd  0      0
UUID=dddd-eeee-ffff                       /mnt/backup   ext4     defaults,noatime                0      2
UUID=1234-5678                            /boot/efi     vfat     umask=0077                      0      1

# Test all fstab entries without rebooting
sudo mount -a

# Verify a specific entry
sudo mount /mnt/backup

💡 Always use UUID (blkid) rather than device names like /dev/sda1 — device names shift when you add or remove drives.

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Disk Usage

# Free space on all mounted filesystems
df -h

# Disk usage of a directory (human-readable, summarized)
du -sh /home

# Top 20 largest directories under /var
du -h /var | sort -rh | head -20

# Interactive disk usage explorer (pre-installed)
ncdu /

# Btrfs-specific: actual space used after compression and deduplication
compsize /home
sudo btrfs filesystem usage /

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SMART — Disk Health Monitoring

SMART (Self-Monitoring, Analysis and Reporting Technology) provides drive health data. smartmontools is pre-installed.

# Quick health summary
sudo smartctl -H /dev/sda

# Full SMART info and attributes
sudo smartctl -a /dev/sda

# NVMe health
sudo smartctl -a /dev/nvme0

# Run a short self-test (takes ~2 minutes)
sudo smartctl -t short /dev/sda

# Run a long self-test (takes hours — run overnight)
sudo smartctl -t long /dev/sda

# Check test results
sudo smartctl -l selftest /dev/sda

# Enable SMART if disabled
sudo smartctl -s on /dev/sda

Automated SMART Monitoring (smartd)

# Enable the smartd daemon to monitor all drives and alert on errors
sudo systemctl enable --now smartd

# Check smartd status
systemctl status smartd

# View smartd alerts
journalctl -u smartd -n 50

The default /etc/smartd.conf monitors all drives and writes to the journal. For email alerts, add -m your@email.com to the DEVICESCAN line.

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NVMe Tools

# List NVMe drives
sudo nvme list

# Health and SMART data
sudo nvme smart-log /dev/nvme0

# Firmware version
sudo nvme id-ctrl /dev/nvme0 | grep -i fw

# Format a namespace (DESTRUCTIVE — erases drive)
sudo nvme format /dev/nvme0 --ses=1

# NVMe error log
sudo nvme error-log /dev/nvme0

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udisks2 — Desktop Storage Layer

udisks2 is the D-Bus service that GNOME Disks, KDE's Removable Media, and file managers use to mount/unmount drives without root.

# List all drives and block devices
udisksctl status

# Mount a drive as your user (no sudo needed)
udisksctl mount -b /dev/sdb1

# Unmount
udisksctl unmount -b /dev/sdb1

# Power off (safely spin down) a USB drive
udisksctl power-off -b /dev/sdb

# Unlock a LUKS volume
udisksctl unlock -b /dev/sdb1

# Show detailed info for a device
udisksctl info -b /dev/sda

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Loop Devices

Loop devices let you mount image files as block devices.

# Attach an image to a loop device
sudo losetup -fP disk.img        # -f = find free, -P = scan partitions

# List active loop devices
losetup -l

# Mount the loop device (or a partition within it)
sudo mount /dev/loop0p1 /mnt

# Detach
sudo losetup -d /dev/loop0

# Create a blank image file (e.g. 2 GiB)
dd if=/dev/zero of=disk.img bs=1M count=2048
# or (sparse, instant):
truncate -s 2G disk.img

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Swap

# Show current swap usage
swapon --show
free -h

# Add a swap file
sudo fallocate -l 4G /swapfile
sudo chmod 600 /swapfile
sudo mkswap /swapfile
sudo swapon /swapfile

# Make permanent (add to /etc/fstab)
echo '/swapfile none swap defaults 0 0' | sudo tee -a /etc/fstab

# Disable a swap file
sudo swapoff /swapfile

# ZRAM swap (Shani OS default)
zramctl                          # show ZRAM devices and compression ratio
cat /proc/swaps                  # all active swap sources

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Troubleshooting

| Issue | Solution | |-------|----------| | umount: target is busy | Find what's using it: lsof +D /mountpoint or fuser -mv /mountpoint; then kill or umount -l | | Drive not appearing in lsblk | Check dmesg | tail -30 for kernel errors; try a different port or cable | | SMART not available | Some USB enclosures block SMART passthrough; try smartctl -d sat /dev/sdb | | e2fsck finds errors but drive is mounted | Boot from the other slot and run e2fsck unmounted | | Btrfs reports errors after scrub | Check dmesg | grep btrfs; if uncorrectable, restore from backup — the drive may be failing | | No space left but df shows free space | Inode exhaustion: df -i; or Btrfs metadata full: sudo btrfs balance start -m / | | UUID changed after mkfs | Update /etc/fstab with blkid; regenerate initramfs with sudo dracut --force |

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