Re: [gentoo-user] btrfs and gcc 4.9

[Stefan G. Weichinger]

Am 08.11.2014 um 21:27 schrieb James:

> If you would be so cool as to post your subvolume setup;
> I'd be very grateful:

[..]

> I guess what really has me "confused" is to set up a traditional
> fstab, uuid, efi,  with grub2. I'm just "dense" I guess
> because the aforementioned doc, I think derived from some
> of "Duncan's"  postings just does not click for me.  I've botched
> a few runs at btrfs (raid1) one on fresh gentoo installs, just
> so you know....

Starting with filesystems like zfs or btrfs means learning new concepts,
yes.

You talk of subvolumes but show partitioning ... right?

OK, what do I have here?

A bit easier as I don't run rootfs on a raid on my main box. I use
btrfs-pools with redundancy as well but not in this case.

The SSD here is partitioned like this:

Found valid GPT with protective MBR; using GPT.
Disk /dev/sda: 488397168 sectors, 232.9 GiB
Logical sector size: 512 bytes
Disk identifier (GUID): 32048E18-BD83-4873-96CF-48D04B8739E6
Partition table holds up to 128 entries
First usable sector is 34, last usable sector is 488397134
Partitions will be aligned on 2048-sector boundaries
Total free space is 2349 sectors (1.1 MiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048          194559   94.0 MiB    EF00  ESI
   2          194560       480585727   229.1 GiB   8300  Linux filesystem
   3       480585728       488396799   3.7 GiB     8200

(partition 3 is just some slice left over afaik)

-

/dev/sda2 went into one of the btrfs "pools" here:

# btrfs fi show
Label: 'btrfs_evo'  uuid: 741835e6-95a3-49f3-ba85-2ffe3ea0730d
	Total devices 1 FS bytes used 58.28GiB
	devid    1 size 229.07GiB used 63.02GiB path /dev/sda2

-

And from here you can start to create and use btrfs-subvolumes.

I currently have the following subvolumes in this pool:

# btrfs su list /
ID 256 gen 56 top level 5 path __active
ID 257 gen 2223 top level 256 path __active/root
ID 275 gen 2224 top level 256 path __active/root_rasa
ID 281 gen 2223 top level 256 path __active/home
ID 312 gen 851 top level 256 path __active/oopsfiles

And then I use them and mount them via /etc/fstab


# grep 741835e6-95a3-49f3-ba85-2ffe3ea0730d /etc/fstab
UUID=741835e6-95a3-49f3-ba85-2ffe3ea0730d	/mnt/btrfs_pool1	btrfs
noauto,noatime,compress=lzo,subvolid=5	0	0

UUID=741835e6-95a3-49f3-ba85-2ffe3ea0730d	/	btrfs
defaults,noatime,compress=lzo,subvolid=257	0	0

UUID=741835e6-95a3-49f3-ba85-2ffe3ea0730d	/home	btrfs
defaults,noatime,compress=lzo,subvolid=281	0	0

UUID=741835e6-95a3-49f3-ba85-2ffe3ea0730d	/home/sgw/oopsfiles	btrfs
defaults,noatime,compress=lzo,subvolid=312	0	0

UUID=741835e6-95a3-49f3-ba85-2ffe3ea0730d	/mnt/root_rasa	btrfs
x-systemd.automount,noatime,compress=lzo,subvolid=275	0	0


A special note here for mountpoint /mnt/btrfs_pool1: with subvolid 5 I
get access to the "root" or top of this btrfs pool: in this mountpoint
you can access all the subvolumes like in a directory tree. I mount it
"noauto" ... I sometimes use this to modify things or work with snapshots.

-

If you set up your btrfs pool with raid1 redundancy this doesn't make
any difference from there. Create subvolumes and mount them where you
need them.

-

Does this help in any way?

Did you create your pool already?

There are lots of things to say here, please let us know where we can
help, learn and share ;-)

Stefan