Disk Management

# Show disk space on all mounted filesystems (human-readable)
$ df -h
Filesystem      Size  Used Avail Use% Mounted on
tmpfs           792M  1.2M  791M   1% /run
/dev/sda1       98G   45G   48G  49% /
tmpfs           3.9G     0  3.9G   0% /dev/shm
tmpfs           5.0M     0  5.0M   0% /run/lock
/dev/sdb1      200G   89G  111G  45% /data
/dev/sdc1       50G    12G   38G  24% /backup

# Show inodes (file count limit, not disk space)
$ df -i
Filesystem       Inodes  IUsed   IFree IUse% Mounted on
/dev/sda1      6553600 234567 6319033    4% /
 
# Show filesystem type
$ df -Th
Filesystem     Type      Size  Used Avail Use% Mounted on
/dev/sda1     ext4       98G   45G   48G  49% /
tmpfs         tmpfs     792M  1.2M  791M   1% /run

# Show size of a directory (human-readable)
$ du -sh /var/log
1.2G    /var/log
 
# Show all directories, sorted by size
$ du -h --max-depth=1 /var | sort -h
4.0K    /var/local
8.0K    /var/opt
64K    /var/cache
1.2G    /var/log
48G    /var/lib
 
# Show top 20 largest items
$ du -h /var 2>/dev/null | sort -rh | head -20

# Find files larger than 100MB
$ find / -type f -size +100M 2>/dev/null
/var/lib/docker/overlay2/abc123.../data.img
/var/log/archive/old-logs.tar.gz
 
# Find files larger than 1GB in /home
$ find /home -type f -size +1G 2>/dev/null
 
# Find the 10 largest files in a directory
$ find /var/log -type f -exec ls -lh {} \; 2>/dev/null | sort -k5 -rh | head -10
 
# Find largest files by extension
$ find / -type f -name "*.log" -size +100M 2>/dev/null

$ lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
sda           8:0    0   100G  0 disk
├─sda1        8:1    0   98G   0 part /
├─sda14       8:14   0     1M   0 part
└─sda15       8:15   0   106M  0 part /boot/efi
sdb           8:16   0   500G  0 disk         ← New unformatted disk
sdc           8:32   0   1TB   0 disk         ← Another new disk

# 1. Create a filesystem (format the partition)
$ sudo mkfs.ext4 /dev/sdb
mke2fs 1.46.5 (30-Dec-2021)
Creating filesystem with 131072000 4k blocks and 32768000 inodes
Filesystem UUID: 3e4a5b6c-7d8e-9f0a-1b2c-3d4e5f6a7b8c
Allocating group tables: done
Writing superblocks and filesystem accounting: done
 
# 2. Create a mount point directory
$ sudo mkdir -p /mnt/data
 
# 3. Mount the filesystem
$ sudo mount /dev/sdb /mnt/data
 
# 4. Verify
$ df -h /mnt/data
Filesystem      Size  Used Avail Use% Mounted on
/dev/sdb       493G   73M  467G   1% /mnt/data

# Unmount when done
$ sudo umount /mnt/data
 
# Force unmount (if busy)
$ sudo umount -f /mnt/data
 
# Lazy unmount (unmount when not busy)
$ sudo umount -l /mnt/data

# Get the UUID of the filesystem
$ sudo blkid /dev/sdb
/dev/sdb: UUID="3e4a5b6c-7d8e-9f0a-1b2c-3d4e5f6a7b8c" TYPE="ext4"
 
# Add to /etc/fstab
$ sudo nano /etc/fstab
# Add this line:
UUID=3e4a5b6c-7d8e-9f0a-1b2c-3d4e5f6a7b8c  /mnt/data  ext4  defaults  0  2

# Test fstab entry without rebooting
$ sudo mount -a
# If no errors, the entry is valid
 
# Verify it mounted
$ df -h /mnt/data

# View partition table
$ sudo fdisk -l /dev/sda
Disk /dev/sda: 100 GiB, 107374182400 bytes, 209715200 sectors
Disk model: Virtual Disk
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
 
Device       Start       End   Sectors  Size  Type
/dev/sda1    2048  20482047   20480000  9.8G  Linux filesystem
/dev/sda2  20482048  40962047   20480000  9.8G  Linux filesystem

# After partitioning, inform the kernel
$ sudo partprobe /dev/sdb

# Show LVM status
$ sudo lvdisplay
 
# Show physical volumes
$ sudo pvdisplay
 
# Show volume groups
$ sudo vgdisplay
 
# Extend a logical volume (while mounted)
$ sudo lvextend -L +50G /dev/vg00/lv_data
$ sudo resize2fs /dev/vg00/lv_data