DAS)¶

4 questions

L0 (1 questions)¶

1. Why should you use UUIDs instead of /dev/sdX names in /etc/fstab?

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Device names like /dev/sda can change between reboots if disks are added, removed, or detected in a different order. UUIDs are unique and stable identifiers tied to the filesystem. Use 'blkid' to find UUIDs.

L1 (1 questions)¶

1. What are the three layers of LVM and how do they relate?

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Physical Volumes (PVs) are raw block devices or partitions. Volume Groups (VGs) pool one or more PVs into a single storage pool. Logical Volumes (LVs) are carved from VGs and are what you format with a filesystem and mount. This layering enables resizing, snapshots, and spanning multiple disks.

L2 (1 questions)¶

1. A server shows 'df -h' at 90% usage but 'du -sh /' only accounts for 60%. What is the most likely cause?

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Deleted files are still held open by running processes. The filesystem reports the space as used (df), but the files no longer appear in the directory tree (du). Use 'lsof +D / | grep deleted' to find the processes holding deleted files. Restarting those processes or truncating via /proc//fd/ reclaims the space.

L3 (1 questions)¶

1. You need to add a new disk to an existing LVM volume group, extend a logical volume, and grow the filesystem online. List the exact commands.

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1. pvcreate /dev/sdb
2. vgextend myvg /dev/sdb
3. lvextend -l +100%FREE /dev/myvg/mylv
4. For ext4: resize2fs /dev/myvg/mylv. For XFS: xfs_growfs /mountpoint. All steps are online — no unmount required.