Convert Raid 1 To Plain Disk
How to convert an MDADM Managed RAID1? drive to a plain disk
Courtesy of:
1 - Stephane Chazelas answer here: https://unix.stackexchange.com/questions/57477/convert-dev-md0-to-dev-sda1
Get data via netcat from other PC:
[root@acer-dt-arch ~]# nc 192.168.200.6 5000 | dd of=/dev/sde2 bs=10M 0+16437776 records in 0+16437776 records out 107374182400 bytes (107 GB, 100 GiB) copied, 10785.6 s, 10.0 MB/s
unplug and re-plug drive:
[root@acer-dt-arch ~]# dmesg ..... [12982.495291] sd 8:0:0:0: [sde] Attached SCSI disk
Cannot directly mount drive:
[root@acer-dt-arch ~]# mount /dev/sde2 /mnt/tmp/ mount: /mnt/tmp: unknown filesystem type 'linux_raid_member'.
Also cannot remove superblock
[root@acer-dt-arch ~]# mdadm --zero-superblock /dev/sde2 mdadm: Couldn't open /dev/sde2 for write - not zeroing
This is because it has already been detected as raid and mdadm initialised:
[root@acer-dt-arch ~]# cat /proc/mdstat
Personalities : [raid1]
md127 : inactive sde2[2](S)
104792064 blocks super 1.2
unused devices: <none>
Get Data Offset of partition (in this case 131072 sectors).
[root@acer-dt-arch ~]# mdadm -E /dev/sde1
/dev/sde1:
MBR Magic : aa55
[root@acer-dt-arch ~]# mdadm --zero-superblock /dev/sde2
mdadm: Couldn't open /dev/sde2 for write - not zeroing
[root@acer-dt-arch ~]# mdadm -E /dev/sde2
/dev/sde2:
Magic : a92b4efc
Version : 1.2
Feature Map : 0x0
Array UUID : eb274c42:226693ba:c781d04c:2cf395c9
Name : archiso:0
Creation Time : Sat Feb 1 18:21:04 2014
Raid Level : raid1
Raid Devices : 2
Avail Dev Size : 209584128 (99.94 GiB 107.31 GB)
Array Size : 104792064 (99.94 GiB 107.31 GB)
Data Offset : 131072 sectors
Super Offset : 8 sectors
State : clean
Device UUID : c9692bec:21c7f2b4:68b3760d:793b370d
Update Time : Sat Dec 29 00:24:36 2018
Bad Block Log : 512 entries available at offset 72 sectors
Checksum : e32bd0fb - correct
Events : 32355
Device Role : Active device 0
Array State : AA ('A' == active, '.' == missing, 'R' == replacing)
Stop array:
[root@acer-dt-arch ~]# mdadm --stop /dev/md127 mdadm: stopped /dev/md127
Now remove superblock (not sure if this is strictly necessary)
[root@acer-dt-arch ~]# mdadm --zero-superblock /dev/sde2
It still won't mount due to the data offset:
[root@acer-dt-arch ~]# mount /dev/sde2 /mnt/tmp/ mount.nilfs2: Error while mounting /dev/sde2 on /mnt/tmp: Invalid argument [root@acer-dt-arch ~]# mount -t ext4 /dev/sde2 /mnt/tmp/ mount: /mnt/tmp: wrong fs type, bad option, bad superblock on /dev/sde2, missing codepage or helper program, or other error.
We need to move the partition along by the offset so that the underlying ext4 filesystem is at the start:
[root@acer-dt-arch ~]# fdisk -u /dev/sde
Welcome to fdisk (util-linux 2.33). Changes will remain in memory only, until you decide to write them. Be careful before using the write command. Command (m for help): p Disk /dev/sde: 111.8 GiB, 120034123264 bytes, 234441647 sectors Disk model: SNA-DC/U Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 512 bytes I/O size (minimum/optimal): 512 bytes / 512 bytes Disklabel type: gpt Disk identifier: 1E62424E-0B97-405A-8799-AE9A4EFFB716 Device Start End Sectors Size Type /dev/sde1 2048 1026047 1024000 500M EFI System /dev/sde2 1026048 210741248 209715201 100G Linux filesystem
Note the start sector of sde2, then add the data offset from above to get the new value for the partition. Then delete and add the new partition with the new start sector. Do not remove the 'signature' when prompted:
Command (m for help): d
Partition number (1,2, default 2): 2
Partition 2 has been deleted.
Command (m for help): n
Partition number (2-128, default 2): 2
First sector (1026048-234441613, default 1026048): 1157120
Last sector, +/-sectors or +/-size{K,M,G,T,P} (1157120-234441613, default 234441613): 210741248
Created a new partition 2 of type 'Linux filesystem' and of size 100 GiB.
Partition #2 contains a ext4 signature.
Do you want to remove the signature? [Y]es/[N]o: n
Command (m for help): p
Disk /dev/sde: 111.8 GiB, 120034123264 bytes, 234441647 sectors
Disk model: SNA-DC/U
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 1E62424E-0B97-405A-8799-AE9A4EFFB716
Device Start End Sectors Size Type
/dev/sde1 2048 1026047 1024000 500M EFI System
/dev/sde2 1157120 210741248 209584129 100G Linux filesystem
Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.
Now your device is a single drive and mountable:
[root@acer-dt-arch ~]# mount -t ext4 /dev/sde2 /mnt/tmp/ [root@acer-dt-arch ~]# ls /mnt/tmp/ bin dead.letter etc lib local media opt root sbin sys usr boot dev home lib64 lost+found mnt proc run srv tmp var