Step‑by‑Step Guide to Expanding and Auto‑Mounting Linux Disks

1. Disk Expansion

Linux partition commands such as fdisk modify the MBR partition table; the MBR format limits a partition size to 2 TB.

1. View start cylinder of /dev/vdc

fdisk -l

vdc1 start sector: 2048, end sector: 1048575999. Record the start value.

2. Disk /dev/vdc has been expanded from 500 GB to 2 TB; now resize the vdc1 partition

3. Unmount the partition

umount /data

4. Resize the partition with fdisk

fdisk /dev/vdc

Use p to print the table, d to delete the existing partition (do not save), then n to create a new primary partition with the same number (1), start sector 2048, and end sector 4194303999 (or the desired size). Finally, wq to write changes.

5. Resize the ext4 filesystem

e2fsck -f /dev/vdc1

(check) and resize2fs /dev/vdc1 (expand).

6. Remount the partition and verify

lsblk

to view size, mount to mount, df -h to check usage.

After these steps vdc1 grows from ~453 GB to ~1.8 TB.

2. Disk Partitioning on /dev/vdb

fdisk -l

to view disks, then fdisk /dev/vdb to create a new primary partition (number 1) with start sector 2048 and end sector 4194303999, followed by wq.

Format the partition:

mkfs.ext4 /dev/sdb1

Mount it to /data: mount /dev/sdb1 /data/ Verify with df -h:

3. Automatic Mount on Boot

Method 1: /etc/fstab

Add an entry to /etc/fstab so the mount persists after reboot.

Method 2: /etc/rc.local

Insert the mount command into /etc/rc.local, which runs as a shell script at startup.

mount /dev/vdb /data/

Method 3: Systemd mount unit

Systemd can manage mounts as services, offering options such as network‑dependent mounting, automatic unmount, and failure handling.

[Unit]
Description=Mount DO Volume volume

[Mount]
What=/dev/disk/by-uuid/d946870c-ef31-48ee-a9f1-446acaa56f46
Where=/mnt/volume
Options=defaults,nofail,discard,noatime
Type=ext4

[Install]
WantedBy=multi-user.target

Control the unit with standard systemctl commands:

systemctl status mnt-volume.mount
systemctl enable mnt-volume.mount
systemctl disable mnt-volume.mount
systemctl start mnt-volume.mount
systemctl stop mnt-volume.mount

Method 4: autofs

Install autofs ( yum install autofs -y) to mount on‑demand when a user accesses the directory.

4. Common Mount Errors and Fixes

4.1 Read‑only (write‑protected) mount

Re‑format the partition with mkfs.ext4 /dev/sdb1 (as described in section 2) and remount.

4.2 Superblock cannot be read

Run a filesystem check, e.g. fsck.ext3 -B 1024 /dev/vdb, then remount.

Regardless of issues, ensure services using the disk (e.g., MySQL, Elasticsearch) are stopped before resizing.

Reference: Original article