EX200 Create and configure file systems Practice Question
During boot, a custom application fails because the /data file system is not mounted. Upon investigation, the administrator sees an error 'UUID=abc123 not found' in the logs. Which command should the administrator use to correct the /etc/fstab entry?
⚠ Common exam trap
Red Hat often tests the distinction between commands that display partition table information (fdisk) versus those that display filesystem metadata (blkid, lsblk -f), and candidates mistakenly choose `fdisk -l` or `lsblk -f` because they see 'UUID' in the output, but `blkid` is the direct, intended tool for retrieving a UUID to fix an fstab entry.
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
✓
blkid /dev/sdb1
The error 'UUID=abc123 not found' indicates that the /etc/fstab entry for /data references a UUID that does not match any block device. The administrator needs to find the correct UUID of the actual partition (e.g., /dev/sdb1) and update the fstab entry. The `blkid /dev/sdb1` command displays the UUID (and filesystem type) of that specific device, allowing the administrator to copy the correct UUID into /etc/fstab.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
blkid /dev/sdb1
Why this is correct
blkid reads the filesystem metadata on a block device and prints the UUID, TYPE, and LABEL directly from the superblock; it does not require the device to be mounted or an entry in /etc/fstab. Running blkid /dev/sdb1 is the correct first step to capture the exact UUID to place in an fstab line, ensuring the mount uses a stable identifier rather than a transient device node.
- ✗
mount -a
Why it's wrong here
mount -a attempts to mount every filesystem listed in /etc/fstab. If the fstab entry for /dev/sdb1 contains an incorrect or missing UUID, mount will fail with a device-not-found error, and the command itself will not tell you the correct value; it only consumes what is already in the file. In a boot-failure scenario the administrator must first query the device with blkid, then correct fstab before mount -a can succeed.
- ✗
xfs_info /dev/sdb1
Why it's wrong here
xfs_info /dev/sdb1 is a diagnostic tool intended solely for XFS filesystems; it reports geometry, block size, and other XFS-specific allocation data, not the filesystem UUID. If /dev/sdb1 holds a non-XFS filesystem (or is not mounted), xfs_info exits with an error, so it cannot serve as a general-purpose UUID query on this device.
- ✗
fdisk -l /dev/sdb1
Why it's wrong here
fdisk -l /dev/sdb1 shows the partition table layout: start/end sectors, size, and partition type ID (such as 83 for Linux) are displayed, but filesystem UUIDs are not part of fdisk's output. fdisk operates on the partition table itself, not the filesystem's superblock, so no UUID of an ext4 or XFS filesystem is revealed. To report the UUID you must use a tool that reads the filesystem metadata, like blkid.
- ✗
lsblk -f /dev/sdb1
Why it's wrong here
lsblk -f /dev/sdb1 does display the filesystem type and UUID in a tree-like format, so it is not useless, but it is an interactive-oriented listing tool rather than the primary command for a single device's raw attributes. Its output is padded and formatted for human readability, whereas blkid emits parsable key=value pairs directly from the device; in an exam or a boot-recovery script, blkid is the standard and more direct way to obtain a UUID.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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