System Administration

System administration covers the day-to-day tasks of maintaining a Linux system — managing disks, monitoring performance, reviewing logs, and securely connecting to remote servers. This lesson brings together the essential tools and practices.

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Disk Management

Viewing Disk Usage

df -h                            # show filesystem disk usage (human-readable)
df -h /                          # show usage for a specific mount point
du -sh /var/log                  # show total size of a directory
du -sh /home/*                   # show size of each user's home directory
du -h --max-depth=1 /var         # show size of immediate subdirectories

Block Devices

lsblk                            # list block devices (disks and partitions)
lsblk -f                         # include filesystem information
sudo fdisk -l                    # detailed partition information
blkid                            # show UUID and filesystem type

Example lsblk output:

NAME    MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda       8:0    0   100G  0 disk
├── sda1  8:1    0   512M  0 part /boot/efi
├── sda2  8:2    0    95G  0 part /
└── sda3  8:3    0   4.5G  0 part [SWAP]
sdb       8:16   0    50G  0 disk
└── sdb1  8:17   0    50G  0 part /data

Mounting and Unmounting