EX200 Operate running systems Practice Question
An ext4 filesystem on a logical volume has been extended with lvextend, but df -h still shows the old size. Which command must be run to make the filesystem aware of the new size?
⚠ Common exam trap
It's easy for candidates to confuse the filesystem-specific commands (resize2fs for ext4 vs. xfs_growfs for XFS) or assume that extending the logical volume automatically resizes the filesystem, which is only true if the `-r` flag is used with `lvextend`.
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
✓
resize2fs
The `resize2fs` command is the correct tool to resize an ext4 filesystem after the underlying logical volume has been extended with `lvextend`. While `lvextend` expands the block device, the filesystem itself is not automatically aware of the new space; `resize2fs` adjusts the filesystem metadata to utilize the additional capacity.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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lvextend -r
Why it's wrong here
lvextend -r combines the two steps: it first expands the logical volume to a specified size and then immediately invokes the filesystem resize tool (for ext4, resize2fs) to match. Because the logical volume has already been enlarged, running lvextend -r now would take the LV size even further, consuming additional free physical extents and possibly producing a filesystem larger than needed. It would have been a correct one-shot solution if used during the initial extension, but after the fact it is the wrong fix because it does not simply reconcile the existing filesystem with the current LV size.
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fsadm resize
Why it's wrong here
fsadm resize is an LVM helper that can resize filesystems, but for ext4 it merely wraps the same resize2fs logic behind a generic interface. The accepted and expected tool in an LVM/ext4 workflow is resize2fs directly; fsadm is intended for automated operations and its documentation points to resize2fs as the definitive ext4 resizer. Using fsadm now could work, but it is not the standard choice and introduces an unnecessary abstraction layer, so it is less precise than the correct answer.
- ✓
resize2fs
Why this is correct
resize2fs is the correct command because the logical volume has already been grown and only the ext4 filesystem's metadata still reflects the old smaller size. Running resize2fs /dev/yourvg/yourlv without a size argument makes the filesystem expand to use all available space in the enlarged logical volume. It can be used online for mounted ext4 filesystems, making it the direct and standard method to complete the extension.
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xfs_growfs
Why it's wrong here
xfs_growfs is specifically designed for the XFS filesystem, which has a different on-disk format, block bitmap structure, and resizing mechanism that relies on the mounted filesystem and magic number checks. It cannot parse or modify an ext4 superblock, block group descriptors, or inode tables, so it would fail immediately with an error indicating the target is not an XFS filesystem. Additionally, xfs_growfs requires a mount point argument rather than a block device, further demonstrating it is not appropriate for ext4.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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