File Systems & Storage Management Flashcards

Which command creates a 2 GB sparse file named 'disk.img' using dd?

Answer: dd if=/dev/zero bs=1 count=0 seek=2G of=disk.img

Using seek=2G with count=0 creates a sparse file by placing the file pointer without writing zeros, consuming no actual disk blocks.

What is the effect of running 'vgreduce vg0 /dev/sdb' without pvmove first?

Answer: Fails if /dev/sdb still holds active physical extents

vgreduce refuses to remove a PV that still contains allocated physical extents; pvmove must be run first.

Which command mounts an ISO image file as a loopback device at /mnt/iso?

Answer: mount -o loop image.iso /mnt/iso

The -o loop option tells mount to use a loop device to mount the image file as if it were a block device.

What does the XFS 'xfs_growfs' command do?

Answer: Expands a mounted XFS filesystem to fill available space on its underlying device

xfs_growfs can expand an XFS filesystem online (while mounted) to use newly added space on the underlying block device.

Which command lists all open files on a specific mount point, useful before unmounting?

Answer: lsof +D /mnt/data

lsof +D recursively lists all open files under a directory, helping identify processes preventing unmount.

In ext4, what is the purpose of the 'reserved blocks' and which command adjusts the percentage?

Answer: Blocks reserved for root to prevent full-disk lockouts; adjusted with tune2fs -m

ext4 reserves a percentage (default 5%) of blocks for the root user; tune2fs -m sets this percentage to maintain root access when the disk is nearly full.

Which command shows the physical extent layout and allocation status of a specific logical volume?

Answer: lvdisplay -m /dev/vg0/lv0

lvdisplay -m (--maps) shows the physical volume mapping for each logical extent of the LV.