How to reformat a partition properly ?

Question

I want to create a case-insensitive partition (not loop-mounted).
To this avail, I created a Ubuntu 16.04 VM in VirtualBox, and I manually partitioned the disk on startup (of Ubuntu-Install), into a 15 GB root partition, 4 GB Swap-Partition and 6 GB JFS partition.

This looks like that

It all works fine, I installed Ubuntu and everything works fine, even after reboot.

Unfortunately, I can't specify -O (case-insensitive) when I create the JFS partition during partition setup.

So after everything is installed, and the operating system is rebooted (successfully), I unmount the partition

umount /web

And recreate it with the -O option (=OS2-compatiblity = case-insensitive)

mkfs.jfs -O /dev/hda5

It says: this will delete all content, I choose [YES].

then I re-mount that filesystem:

mount /dev/hda5 /web

After /web is mounted, I create a file/folder called "Test" into /web, and then I try to create another file/folder called "test" in /web, and then it says: error, file already exists.
Superb, works as it should - file-system is case-insensitive.

But when I restart, I get

Welcome to emergency boot mode...

and then, you basically can't do anything except deleting the VM, and re-importing the backup copy.

Why do I get emergency-boot-mode ?
The root file-system at / which contains all the boot-stuff should not even be affected by any of the changes I made...
What am I missing ?
How to get this to work ?

Answer 1

is /web partiton automatically mounted? when you remake the partition it changes the uuid you have to update /etc/fstab with the new uuid.

EDIT: yes I see the lines, the system is crashing because it can't find /web by uuid. and since it is in fstab it is considered a dependant mount.

Answer 2

Not that I recommend it wholeheartedly, but you can also run jsf_tune to reuse the UUID of the old filesystem. jsf_tune is provided by jfsutils (sudo apt install jfsutils) in all currently supported versions of Ubuntu.

# blkid /dev/hda5
/dev/hda5: UUID="e034928e-a30c-4d0e-82e4-2970204d6b1f" BLOCK_SIZE="4096" TYPE="jfs"
# mkfs.jfs -O /dev/hda5
…
# jfs_tune -U "e034928e-a30c-4d0e-82e4-2970204d6b1f" /dev/hda5
jfs_tune version 1.1.15, 04-Mar-2011
UUID updated successfully.

Now you don't have to update /etc/fstab.