LPIC-2 Practice Question: Block Devices, Filesystems and Advanced Storage
An organization runs a critical application on a Linux server that stores its data on a 500GB LVM logical volume named /dev/vg_data/lv_app. The application must remain operational with minimal disruption, so unmounting the volume is not acceptable. The administrator needs to create a full backup of the logical volume to an external 1TB USB drive attached via eSATA. The backup must capture a point-in-time consistent state of the filesystem. The logical volume is formatted with XFS. Which of the following procedures best achieves this goal while minimizing downtime?
⚠ Common exam trap
Candidates often think dd can safely clone a mounted filesystem, but they overlook the need for filesystem-level consistency, which LVM snapshots provide without requiring unmounting.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Create an LVM snapshot volume of /dev/vg_data/lv_app, mount the snapshot to a temporary directory, and use rsync to copy the data to the USB drive.
It uses an LVM snapshot to capture a point-in-time consistent state of the XFS filesystem without unmounting the original volume. The snapshot is mounted read-only, and rsync copies the data to the USB drive, ensuring minimal disruption to the running application. This approach leverages LVM's copy-on-write mechanism to freeze the filesystem state at the snapshot creation moment.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Unmount the logical volume, use tar to create an archive on the USB drive, then remount the volume.
Why it's wrong here
Unmounting causes application downtime; the goal is minimal disruption.
- ✗
Use dd to clone the logical volume directly to the USB drive while the volume is mounted.
Why it's wrong here
dd reads the raw device while it is being written to, leading to inconsistent data.
- ✗
Create an LVM snapshot volume and then use cp -a to copy the snapshot volume's contents directly without mounting.
Why it's wrong here
cp -a on a block device does not work; you must mount the snapshot to access the filesystem.
- ✓
Create an LVM snapshot volume of /dev/vg_data/lv_app, mount the snapshot to a temporary directory, and use rsync to copy the data to the USB drive.
Why this is correct
The snapshot is consistent, mounting it does not affect the live volume, and rsync ensures accurate copying.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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