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Storage / Stage 6 of 11

Logical volumes and growing a filesystem

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Step 1 of 7 · on a machine · 4 min

The volume is full, yet there is room

What you will learn

  • Use lsblk, vgs and lvs to find which layer holds the free space.
  • Give a volume its final size and count the extents it needs.
  • Grow a volume and its ext4 and check both layers with lvs and df.

A service writes its data to /mnt/lvm-data, and the writes have stopped going through. The device under that directory was sized with room to spare.

Try writing a line, check how much space the volume has, and print the device tree with lsblk.

Exercise · look

Write a line and look at the devices

Try writing a line to /mnt/lvm-data/report.txt, look at df -h for /mnt/lvm-data and at the lsblk device tree. Delete nothing.

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Check yourself 1 question

loop0 is 384M, the data volume on it is 128M, and the volume is full. Where is the rest of the device's space?

  • ext4 keeps its metadata inside the volume, which is why df -h shows a Size of 104M for a 128M volume. Outside the volume ext4 stores nothing.

  • lsblk shows 32M for keep: together with data that is 160M of 384M.

  • lsblk rounds to the megabyte, not by a factor of three: 384M means 384 MiB, three times the volume.

More than 200M of the device belongs to no volume, so the filesystem on data cannot use it.

Found an inaccuracy? Report an error in the lesson

Ubuntu 24.04
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