When installing SLE12 using defaults, the root file system is formatted as BTRFS. BTRFS has many nice features, an instant snapshot capability and the ability to rollback changes in system if using the snapper tool.
However, BTRFS is still too early to call the enterprise FS. Let others debug it, and we will transfer our already installed system to the proven EXT3 FS.
NOTE: my demo system runs on PowerKVM, so the disk is displayed as vda, not sda.
First of all, care about enough space to create a new logical volume. Perhaps you already have it. You can reduce the size of BTRFS online, and then reduce its LV. You can add more disk space, increase the size of the second partition (requires a reboot), and then issue a "pvresize" command.
linux-fb2e:~ # pvs PV VG Fmt Attr PSize PFree /dev/vda2 system lvm2 a-- 19.99g 8.00m linux-fb2e:~ # pvresize /dev/vda2 Physical volume "/dev/vda2" changed 1 physical volume(s) resized / 0 physical volume(s) not resized linux-fb2e:~ # pvs PV VG Fmt Attr PSize PFree /dev/vda2 system lvm2 a-- 29.99g 10.01g
Create a new LV to be the new root FS and format it:
linux-fb2e:~ # lvcreate -L8g -n slash /dev/system Logical volume "slash" created. linux-fb2e:~ # mkfs.ext3 -j /dev/system/slash ..
Mount the destination and source filesystems to be copied by rsync. The order of mount is important, otherwise you can get an infinite loop. Then copy files by rsync:
linux-fb2e:~ # mkdir /mnt/{s,d}
linux-fb2e:~ # mount /dev/system/slash /mnt/d
linux-fb2e:~ # mount -o bind / /mnt/s
linux-fb2e:~ # rsync -av /mnt/s/ /mnt/d/
Prepare the chroot environment. It is required for rebuild initrd that suits for our new configuration:
linux-fb2e:~ # cd /mnt/d linux-fb2e:/mnt/d # mount -t sysfs sysfs sys linux-fb2e:/mnt/d # mount -t proc proc proc linux-fb2e:/mnt/d # mount -o bind /dev dev linux-fb2e:/mnt/d # mount -o bind /dev/pts dev/pts linux-fb2e:/mnt/d # chroot . linux-fb2e:/ # PS1="Chroot# " Chroot#
Now, edit the /etc/fstab to remove all BTRFS mounts and replace them with one:
Chroot# vi /etc/fstab Chroot# cat /etc/fstab /dev/system/swap swap swap defaults 0 0 /dev/system/slash / ext3 defaults 1 2
Rebuild initrd in chrooted environment:
Chroot# cd /boot Chroot# mkinitrd Creating initrd: /boot/initrd-4.4.21-69-default .. dracut: *** Creating initramfs image file '/boot/initrd-4.4.21-69-default' done ***
Leave chroot and copy resulting initrd to original /boot with ".new" extention:
Chroot# exit exit linux-fb2e:/mnt/d # cp /mnt/d/boot/initrd-4.4.21-69-default /boot/initrd-4.4.21-69-default.new
Edit original /boot/grub2/grub.cfg. Duplicate the first "menuentry" of SLES, keep original entry as is, in copy replace the root= entry and initrd name, like:
..
### BEGIN /etc/grub.d/10_linux ###
menuentry 'SLES_SAP 12-SP2 NEW' --class sles_sap --class gnu-linux --class gnu --class os $menuentry_id_option 'gnulinux-simple-dcbb814a-e17c-4173-808b-25e8d45eebbb' {
set gfxpayload=text
insmod gzio
insmod part_msdos
insmod lvm
insmod btrfs
set root='lvmid/2y8FbM-A0z1-4uKh-u45E-HKDX-21n2-KbgjjL/aizFtx-Ulba-QQc2-ubD2-JUd1-jy4P-qDjMT8'
if [ x$feature_platform_search_hint = xy ]; then
search --no-floppy --fs-uuid --set=root --hint='lvmid/2y8FbM-A0z1-4uKh-u45E-HKDX-21n2-KbgjjL/aizFtx-Ulba-QQc2-ubD2-JUd1-jy4P-qDjMT8' dcbb814a-e17c-4173-808b-25e8d45eebbb
else
search --no-floppy --fs-uuid --set=root dcbb814a-e17c-4173-808b-25e8d45eebbb
fi
echo 'Loading Linux 4.4.21-69-default ...'
linux /boot/vmlinux-4.4.21-69-default root=/dev/mapper/system-slash ${extra_cmdline} splash=silent quiet showopts
echo 'Loading initial ramdisk ...'
initrd /boot/initrd-4.4.21-69-default.new
}
..
It's time for the first reboot to the new root FS. If something went wrong, you always can use the original grub entry to fix the problems.
At the moment, we booted into the new root FS using the old grub bootloader.
linux-fb2e:~ # df / Filesystem 1K-blocks Used Available Use% Mounted on /dev/mapper/system-slash 8125880 5028516 2677936 66% /
Remove the old BTRFS root FS to help grub installer understand the required configuration. This is a dangerous part, do not miss a single phase:
linux-fb2e:~ # lvs LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert root system -wi-a----- 19.55g slash system -wi-ao---- 8.00g swap system -wi-ao---- 440.00m linux-fb2e:~ # lvremove /dev/system/root Do you really want to remove active logical volume root? [y/n]: y Logical volume "root" successfully removed
Now rebuild the /boot/grub2/grub.cfg using automatic tools:
linux-fb2e:~ # grub2-mkconfig > /boot/grub2/grub.cfg Generating grub configuration file ... Found linux image: /boot/vmlinux-4.4.21-69-default Found initrd image: /boot/initrd-4.4.21-69-default done
Finally, install the grub bootloader based on the new configuration. It should be installed in the first partition of the "PPC PReP Boot" type, unlike Intel-based systems. So, the command will be:
linux-fb2e:~ # grub2-install /dev/vda1 Installing for powerpc-ieee1275 platform. Installation finished. No error reported.
Make a final reboot.