Levels 29–34: Storage & Filesystems

Level 29: Disks & Partition Tables

Know what’s actually attached to the box before you touch it.

Command	What it does	Why it matters
`fdisk -l /dev/sda`	List a disk’s partition table (MBR/GPT)	The classic partition inspector
`parted -l`	List every disk’s partition table	Handles GPT natively, safe past 2TB
`blkid`	Show device, UUID, and filesystem type	Confirms what’s on a disk before formatting
`lsblk -f`	Block device tree with filesystem/mount info	One view of everything attached
`cat /proc/partitions`	Kernel’s live partition list	Ground truth when a tool’s cache is stale

Level 30: Partitioning with parted & fdisk

parted does it in one line, fdisk drops you into an interactive prompt.

Command	What it does	Why it matters
`parted /dev/sdb mkpart primary ext4 0% 100%`	Create a partition, non-interactively	Scriptable, no keystrokes to remember
`n` (inside fdisk)	Start a new partition	fdisk’s core command
`w` (inside fdisk)	Write changes and exit	Nothing is written until this
`partprobe /dev/sdb`	Force the kernel to reread the partition table	No reboot needed after repartitioning
`parted /dev/sdb rm 1`	Delete a partition by number	Destructive, double-check the number

Level 31: Filesystems & Formatting

A blank partition is just an empty container until it has a filesystem.

Command	What it does	Why it matters
`mkfs.ext4 /dev/sdb1`	Format as ext4	The safe, mature Linux default
`mkfs.xfs /dev/sdc1`	Format as XFS	Better for large files, harder to shrink
`mkswap /dev/sdb2`	Prepare a swap partition	Doesn’t activate it yet
`swapon /dev/sdb2`	Activate swap	Add to fstab to survive a reboot
`fsck -y /dev/sdb1`	Check and auto-repair a filesystem	Never run on a mounted filesystem

Level 32: Mounting & /etc/fstab

A formatted partition still isn’t usable until it’s mounted somewhere.

Command	What it does	Why it matters
`mount /dev/sdb1 /mnt/data`	Mount a device at a path	Mount point must already exist
`umount /mnt/data`	Unmount cleanly	`lsof +D <path>` finds what’s blocking it
`blkid /dev/sdb1`	Get a device’s UUID	Use UUIDs in fstab, not device names
`mount -a`	Mount everything in /etc/fstab	Tests fstab without rebooting
`mount -o remount,rw /`	Remount root read-write in place	First move after an unclean shutdown

Level 33: LVM: Volumes & Groups

An abstraction layer between physical disks and the filesystems on them.

Command	What it does	Why it matters
`pvcreate /dev/sdb1`	Mark a device as an LVM physical volume	The bottom layer of LVM
`vgcreate data_vg /dev/sdb1`	Pool physical volumes into a volume group	A group of storage to carve from
`lvcreate -L 10G -n data_lv data_vg`	Carve a logical volume	Resizable, unlike a real partition
`mkfs.ext4 /dev/data_vg/data_lv`	Format the logical volume	Same mkfs, an LVM path instead
`vgs` / `vgdisplay`	List volume groups	Short summary vs verbose detail

Level 34: LVM: Resize & Snapshots

Today’s sizing decision doesn’t have to be final.

lvextend -L +5G /dev/data_vg/data_lv   # grow the logical volume
resize2fs /dev/data_vg/data_lv         # grow the filesystem to match
vgextend data_vg /dev/sdc1             # add more physical volumes to the pool
lvcreate -L 2G -s -n data_snap /dev/data_vg/data_lv   # snapshot before a risky change
lvremove /dev/data_vg/data_snap        # clean up when it's no longer needed