Mounting & Filesystem Management

Intermediate Linux Server
mountumountfstabblkiddfdu

Objective

Mount filesystems manually and persistently via /etc/fstab, understand filesystem types, and manage disk space.

Tools & Technologies

  • mount
  • umount
  • fstab
  • blkid
  • df
  • du

Key Commands

mount -t ext4 /dev/sdb1 /mnt/data
blkid /dev/sdb1
df -hT
du -sh /var/*
mount -a

Architecture Overview

sequenceDiagram participant A as Admin participant K as Kernel participant VFS as VFS Layer participant FS as Filesystem Driver participant D as Block Device A->>K: mount /dev/sdb1 /mnt/data K->>D: Read superblock D-->>K: Filesystem metadata K->>FS: Load ext4 driver FS->>VFS: Register mount point VFS-->>A: /mnt/data accessible Note over A,D: All file ops go through VFS → FS driver → device

Step-by-Step Process

01
Manual Mount

Mount a filesystem to a directory. Changes are temporary (lost on reboot).

# Mount ext4 partition
sudo mount -t ext4 /dev/sdb1 /mnt/data

# Mount with options
sudo mount -o ro,noexec /dev/sdb1 /mnt/data  # read-only
sudo mount -o remount,rw /mnt/data            # remount rw

# View mounted filesystems
mount | grep sdb
df -hT
02
Persistent Mounts via /etc/fstab

fstab entries survive reboots. Always use UUID, never /dev/sdX names.

# Get UUID
blkid /dev/sdb1
# UUID=abc123...

# Add to /etc/fstab:
# UUID=abc123 /data ext4 defaults 0 2

# Test fstab without rebooting
sudo mount -a

# fstab fields:
# device  mountpoint  fstype  options  dump  pass
03
Disk Space Management

Monitor disk usage and find what's consuming space.

df -h            # filesystem usage
df -hT           # include filesystem type

# Find large directories
du -sh /var/*    # dirs in /var
du -sh /* 2>/dev/null | sort -rh | head

# Find large files
find / -type f -size +100M 2>/dev/null | sort -k5 -rn

Challenges & Solutions

  • Wrong UUID in fstab causes boot failure — use emergency mode to fix
  • mount -a skips entries with noauto option

Key Takeaways

  • nofail option in fstab prevents boot failure if device is absent (good for USB)
  • pass field 2 enables fsck check on boot — set 0 to disable for non-root