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Btrfs with Multiple Devices on LUKS
!! this is a mini howto – be careful !!
Below are my steps for creating an encrypted btrfs raid1 partition.
Contents
Identify the disks
# dmesg | grep disk sd 2:0:0:0: [sdd] 488397168 512-byte logical blocks: (250 GB/232 GiB) sd 3:0:0:0: [sde] 488397168 512-byte logical blocks: (250 GB/232 GiB)
verify the disks by model
# find /sys/devices -type f -name model -exec cat {} \;
VB0250EAVER
VB0250EAVERCreate Random Encrypted keys
by running dd against urandom
dd if=/dev/urandom of=/etc/crypttab.keys/sdd bs=4096 count=1 dd if=/dev/urandom of=/etc/crypttab.keys/sde bs=4096 count=1
(folder /etc/crypttab.keys must exist – otherwise created it first)
and encrypt both disks with the above generated keys
# cryptsetup luksFormat /dev/sdd --key-file /etc/crypttab.keys/sdd WARNING! ======== This will overwrite data on /dev/sdd irrevocably. Are you sure? (Type uppercase yes): YES YES # cryptsetup luksFormat /dev/sde --key-file /etc/crypttab.keys/sde WARNING! ======== This will overwrite data on /dev/sde irrevocably. Are you sure? (Type uppercase yes): YES YES
Verify Encrypted disks
as root you have to see two new unique identifiers for the encrypted disks:
# blkid | tail -2 /dev/sdd: UUID="40258c46-4e6b-47b9-81fc-7247d9cb4968" TYPE="crypto_LUKS" /dev/sde: UUID="e2d6b4ad-9b9c-4a07-bf92-af2597bb1c4a" TYPE="crypto_LUKS"
Try opening and mapping the encrypted disk with the encrypted keys – using the identifiers:
# cryptsetup luksOpen /dev/disk/by-uuid/40258c46-4e6b-47b9-81fc-7247d9cb4968 sdd -d /etc/crypttab.keys/sdd # cryptsetup luksOpen /dev/disk/by-uuid/e2d6b4ad-9b9c-4a07-bf92-af2597bb1c4a sde -d /etc/crypttab.keys/sde
verify the status of the mapped encrypted drives:
# cryptsetup status /dev/mapper/sdd /dev/mapper/sdd is active. type: LUKS1 cipher: aes-xts-plain64 keysize: 256 bits device: /dev/sdd offset: 4096 sectors size: 488393072 sectors mode: read/write # cryptsetup status /dev/mapper/sde /dev/mapper/sde is active. type: LUKS1 cipher: aes-xts-plain64 keysize: 256 bits device: /dev/sde offset: 4096 sectors size: 488393072 sectors mode: read/write
Format
Now it's the time to format the new encrypted map drives under btrfs into a raid-1 setup:
# mkfs.btrfs -L VB0250EAVER -m raid1 -d raid1 /dev/mapper/sdd /dev/mapper/sde WARNING! - Btrfs v3.14.2 IS EXPERIMENTAL WARNING! - see http://btrfs.wiki.kernel.org before using Turning ON incompat feature 'extref': increased hardlink limit per file to 65536 adding device /dev/mapper/sde id 2 fs created label VB0250EAVER on /dev/mapper/sdd nodesize 16384 leafsize 16384 sectorsize 4096 size 465.77GiB Btrfs v3.14.2
Verify that the encrypted map drives have created a new btrfs unique identifier:
# blkid | tail -2 /dev/mapper/sdd: LABEL="VB0250EAVER" UUID="e1408bb9-ad10-48f8-af7e-b86bf2866ef7" UUID_SUB="27fa4119-ea66-4dea-a3d7-0a43b7adc24d" TYPE="btrfs" /dev/mapper/sde: LABEL="VB0250EAVER" UUID="e1408bb9-ad10-48f8-af7e-b86bf2866ef7" UUID_SUB="8ea7256b-4264-4d32-811c-1e35039f006d" TYPE="btrfs"
as you can see, both encrypted map drives have the same UUID – but different subvolumes UUID.
Mount the new disk
Create a new directory
# mkdir -pv /mnt/VB0250EAVER
and add a new line (like the below) at the end of your fstab file:
# echo "UUID=e1408bb9-ad10-48f8-af7e-b86bf2866ef7 /mnt/VB0250EAVER auto defaults,noauto,user,exec 0 0" >> /etc/fstab
Now you can mount the encrypted btrfs raid1 new disk !
# mount /mnt/VB0250EAVER/
Disk Usage
at first let's find out how storage is being used:
# df -h /mnt/VB0250EAVER/ Filesystem Size Used Avail Use% Mounted on /dev/mapper/sdd 466G 1,3M 464G 1% /mnt/VB0250EAVER
btrfs df shows:
# btrfs filesystem df /mnt/VB0250EAVER Data, RAID1 : total=1.00GiB, used=512.00KiB Data, single: total=8.00MiB, used=0.00 System, RAID1 : total=8.00MiB, used=16.00KiB System, single: total=4.00MiB, used=0.00 Metadata, RAID1 : total=1.00GiB, used=112.00KiB Metadata, single: total=8.00MiB, used=0.00
and
# btrfs filesystem show /mnt/VB0250EAVER Label: 'VB0250EAVER' uuid: e1408bb9-ad10-48f8-af7e-b86bf2866ef7 Total devices 2 FS bytes used 640.00KiB devid 1 size 232.88GiB used 2.03GiB path /dev/mapper/sdd devid 2 size 232.88GiB used 2.01GiB path /dev/dm-4 Btrfs v3.14.2
all seems nice !
Be aware on df, you will see the entire disk storage and not the raid1.
This is confusing, i know !
With btrfs you have to ignore df .
Make some noise
Let's create a 100Mb test file under our new encrypted btrfs raid1 disk:
# dd if=/dev/zero of=/mnt/VB0250EAVER/test bs=1024 count=102400 102400+0 records in 102400+0 records out 104857600 bytes (105 MB) copied, 0,290163 s, 361 MB/s
df will NOT show immediately the disk usage:
# df -h /mnt/VB0250EAVER/ Filesystem Size Used Avail Use% Mounted on /dev/mapper/sdd 466G 1,3M 464G 1% /mnt/VB0250EAVER
Sync the disk and run it again:
# sync # df -h /mnt/VB0250EAVER/ Filesystem Size Used Avail Use% Mounted on /dev/mapper/sdd 466G 202M 464G 1% /mnt/VB0250EAVER
Some last info
btrfs df
# btrfs filesystem df /mnt/VB0250EAVER Data, RAID1 : total=1.00GiB, used=100.50MiB Data, single: total=8.00MiB, used=0.00 System, RAID1 : total=8.00MiB, used=16.00KiB System, single: total=4.00MiB, used=0.00 Metadata, RAID1 : total=1.00GiB, used=224.00KiB Metadata, single: total=8.00MiB, used=0.00
btrfs show:
# btrfs filesystem show Label: 'VB0250EAVER' uuid: e76cefe1-7ce3-43fa-953a-31602616d9ca Total devices 2 FS bytes used 100.77MiB devid 1 size 232.88GiB used 2.03GiB path /dev/mapper/sdd devid 2 size 232.88GiB used 2.01GiB path /dev/dm-4 Btrfs v3.14.2