Description
This page describes a test case for bcache-tools: "/ on bcache using LVM"
Bcache is a Linux kernel block layer cache. It allows one or more fast disk drives such as flash-based solid state drives (SSDs) to act as a cache for one or more slower hard disk drives. The bcache-tools package contains the utilities for manipulating bcache
Testing covers not only bcache-tools but also the interaction between bcache-tools and other packages: kernel, util-linux, dracut and lvm2.
Starting with a stable system with /home on LVM on bcache, we can go forward and have / on bcache. Consider thought that bcache is EXPERIMENTAL!
Prerequisites
This test requires the following test case as preparation: /home on bcache (LVM). Furthermore it requires the volume group BCACHE to have at least 2 GB free space!
Setup
If you haven't done so, you should first execute the use case /home on bcache (LVM).
How to test
To get / on bcache:
- create a Logical Volume:
lvcreate -L 2G -n ROOTFS BCACHE - create a filesystem:
mkfs -t ext4 -L ROOTFS /dev/BCACHE/ROOTFS - mount it:
mount /dev/BCACHE/ROOTFS /mnt - copy your current root filesystem to /mnt:
cp -ax / /mnt - edit /mnt/fstab so your root fs is mounted like:
LABEL=ROOTFS / ext4 defaults 1 1
Now we have a duplicate root filesystem on /dev/BCACHE/ROOTFS. To use it we need to build a new initramfs:
- rename your current initramfs:
mv /boot/initramfs...img /boot/initramfs...img.sav - build a new initramfs:
dracut -N
Now reboot your system.
- while booting edit the default grub entry and replace the root=UUID=... parameter in the "linux" line by: root=LABEL=ROOTFS
- remove any rd.lvm=0 occurrence
- now start the modified grub entry
If all goes well, your system now boots fine and it's running on bcache!
- Edit your /etc/grub2.cfg file..
- .. duplicate the first "menuentry ... { ...}" (about 15 lines).
- Now change the first one and replace the root=UUID=... parameter in the "linux" line by root=LABEL=ROOTFS
- reboot your system to see if it boots OK.
- do some other testing if you like.
Expected Results
- All steps complete without errors