On Fri, Jan 31, 2014 at 11:13:41AM -0700, Michael Torrie wrote:
Question is, has anyone been using btrfs for root, and if so what volume
and subvolume layouts did you use? I will be keeping my home
directories on a completely separate partition/volume. But on root,
should I have a separate volume for /var?
I've played around a little with btrfs on an old workstation using Arch,
but I admit I don't have it perfect yet (I can't get the machine to
power off cleanly for some reason). My setup is a little different than
yours, but here it is:
$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sdb 8:16 0 136.8G 0 disk
├─sdb1 8:17 0 1007K 0 part
├─sdb2 8:18 0 100M 0 part
│ └─md127 9:127 0 99.9M 0 raid1 /boot
├─sdb3 8:19 0 2G 0 part [SWAP]
└─sdb4 8:20 0 134.5G 0 part /home
sdc 8:32 0 136.8G 0 disk
├─sdc1 8:33 0 1007K 0 part
├─sdc2 8:34 0 100M 0 part
│ └─md127 9:127 0 99.9M 0 raid1 /boot
├─sdc3 8:35 0 2G 0 part [SWAP]
└─sdc4 8:36 0 134.5G 0 part
I have two SCSI drives (I did say it was an old workstation) and
basically am using RAID-1. The drives are partitioned with a GPT layout
and I use grub, so /dev/sd{b,c}1 is the BIOS boot partition for grub.
/dev/sd{b,c}2 is an ext3 /boot partition, using md-raid in RAID-1.
/dev/sd{b,c}3 are swap partitions, no explicit raid, but both are used
(if needed). Finally, /dev/sd{b,c}4 is my btrfs filesystem.
The single filesystem has two subvolumes, for / and for /home:
$ sudo btrfs subvol list /
ID 258 gen 10556 top level 5 path root
ID 259 gen 10556 top level 5 path home
The root and home partitions are mounted as follows (I replaced the
UUIDs with dummy values here):
$ cat /etc/fstab
# <file system> <dir> <type> <options> <dump> <pass>
# /dev/sdb3
UUID=xxx / btrfs
rw,noatime,autodefrag,space_cache,subvol=root,user_xattr 0 0
# /dev/sdb3
UUID=yyy /home btrfs
rw,noatime,autodefrag,space_cache,subvol=home,user_xattr 0 0
Note that the kernel commandline needs to be modified to mount / from a
subvol:
$ cat /proc/cmdline
BOOT_IMAGE=/vmlinuz-linux root=UUID=xxx rw rootflags=subvol=root
Grub is smart enough to detect this and add these flags for me
automatically.
From what I've seen, everything runs great except for the issue of
cleanly halting the machine. I'll fix that later if/when I have the
time/interest. It's been fun playing around with btrfs, but in some
respects ZFS seems better to me.
--
Rich
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