Expand a Filesystem on CentOS Linux

This is an example on the classic scenario as to how to expand /dev/sdb because you have ran out of space. You now have more space, you just have to tell the filesystem about it.

the first thing we need to do is un-mount the filesystem (otherwise a tragedy will almost certainly happen)

umount /mnt/SDB (or wherever sdb is mounted to) – note it’s “u-mount” not “un-mount”

once your filesystem is unmounted, we can proceed with the next steps

first we need to do a fileystem check /f for force

e2fsck -f /dev/sdb

this will search from block 0, to the end, and find out there is more space oddly enough allocated to /dev/sdb

The manual specifies to run it twice or it will not work (i tried it just to see, no joke, you need to run it twice) 

now we will run

resize2fs /dev/sdb to actually do the resize

it will say resizing to 4k blocks

Once completed it should then say “filesystem on /dev/sdb is now  xxxxxxxxxx(will be different depending on how much space is added) Blocks Long

now if we do a df -h

we can see that our filesystem has increased from 600GB to around 1TB

That’s it!

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