Lab 16.1 : logical volume based on 2 partitions of a single loop device is no mounted on boot
Hello,
I completed the Lab 16.1 with a setup based on a loop device with 2 partitions. The volume group is created from /dev/loop1p1 /dev/loop1p2 and everything is working.
However I dont know how to do it persists between boots.
My guess is that fstab is trying to mount the logical volume but the 2 loop-partitions are not available. I suspect that losetup should be run at some point during boot before /etc/fstab enters into play.
Could you help me (or point me in the right direction) to make the logical volume persists between boots. I know that this is not a typical setup, but I want to understand if this path is possible or not and what is the reason.
Thanks in advance
These are the commands I followed
#create loop device and partitions
dd if=/dev/zero of=/imagefile2 bs=1M count=1024
fdisk /imagefile2
...
Device Boot Start End Blocks Id System
/imagefile2p1 2048 514047 256000 8e Linux LVM
/imagefile2p2 514048 1026047 256000 8e Linux LVM
#setup loop device
losetup --show --partscan --find /imagefile2
> /dev/loop1
#Now create the physical volumes
pvcreate /dev/loop1p1
pvcreate /dev/loop1p2
pvdisplay
#create virtual groups
vgcreate myvg /dev/loop1p1 /dev/loop1p2
vgdisplay
#create logical volumes. Ex 300Mb
lvcreate -L 300M -n mylvm myvg
lvdisplay
#partition the logical volume
mkfs.ext4 /dev/myvg/mylvm
#mount
echo "/dev/myvg/mylvm /mnt/mylvm ext4 defaults 0 0" >> /etc/fstab
mkdir -p /mnt/mylvm
mount -a
Comments
-
Hi,
You may try to add the loop device to /etc/fstab, and it should work after a restart. But I'm not sure if it's going to be ready to be part of a LVM group. But you can try
Regards,
Luis.
0 -
Thanks Luis. No luck.
I tried to mount the loop device in fstab but it failed. The problem is that the loop device has not filesystem itself, but it is made of 2 partitions of type 8e. So the following fails
/imagefile2 /mnt/tempdir2 ext4 loop,rw 1 2
/dev/myvg/mylvm /mnt/mylvm ext4 defaults 0 2I guess that the solucion is in executing
losetup --show --partscan --find /imagefile2
during boot (and before /etc/fstab starts mounting the partitions or at least before the logical volume is mounted).
I dont know if it is possble, and I lack the knowledge of the booting process for doing this.
Another option would be mounting it via a systemd that executes the losetup, but it looks a bit hacky.
I think it is enough for an scenario that does not reflect a real use case. In a real world I would have 2 real disks.
Thanks
0 -
Yeah, you may need to create a service, so you can get the device ready at the right time. If you have time you can play with it. If not, a better possibility is to resize the hard disk, so you can have enough space to create a couple of partitions.
Regards,
Luis.
0
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