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Revision as of 12:42, 12 October 2013 by Rolffokkens (talk | contribs)


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:

  1. create a Logical Volume: lvcreate -L 2G -n ROOTFS BCACHE
  2. create a filesystem: mkfs -t ext4 -L ROOTFS /dev/BCACHE/ROOTFS
  3. mount it: mount /dev/BCACHE/ROOTFS /mnt
  4. copy your current root filesystem to /mnt: cp -ax / /mnt
  5. 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:

  1. rename your current initramfs: mv /boot/initramfs...img /boot/initramfs...img.sav
  2. build a new initramfs: dracut -N

Now reboot your system.

  1. while booting edit the default grub entry and replace the root=UUID=... parameter in the "linux" line by: root=LABEL=ROOTFS
  2. remove any rd.lvm=0 occurrence
  3. now start the modified grub entry

If all goes well, your system now boots fine and it's running on bcache!

  1. create a new /etc/grub2.cfg file: grub2-mkconfig > /etc/grub2.cfg
  2. rename your current initramfs (again): mv /boot/initramfs...img /boot/initramfs...img.sav
  3. build a new initramfs with only the needed drivers included: dracut

Now your system should be ready!

  1. reboot your system to see if it boots OK.
  2. do some other testing if you like.

Expected Results

  1. All steps complete without errors



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