On 2/26/19 6:37 AM, Simon Matter via CentOS wrote:
How is it not systemd doing it? Such things didn't happen with pre systemd
distributions.
The following log is from a CentOS 6 system. I created RAID devices on
two drives. I then stopped the RAID devices and 'dd' over the beginning
of the drive. I then re-partition the drives.
At that point, the RAID devices auto-assemble. They actually partially
fail, below, but the behavior that this thread discusses absolutely is
not systemd-specific.
What you're seeing is that you're wiping the partition, but not the RAID
information inside the partitions. When you remove and then re-create
the partitions, you're hot-adding RAID components to the system. They
auto-assemble, as they have (or should have) for a long time. It's
probably more reliable under newer revisions, but this is long-standing
behavior.
The problem isn't systemd. The problem is that you're not wiping what
you think you're wiping. You need to use "wipefs -a" on each partition
that's a RAID component first, and then "wipefs -a" on the drive itself
to get rid of the partition table.
[root@localhost ~]# dd if=/dev/zero of=/dev/vdb bs=512 count=1024
1024+0 records in
1024+0 records out
524288 bytes (524 kB) copied, 0.0757563 s, 6.9 MB/s
[root@localhost ~]# dd if=/dev/zero of=/dev/vdc bs=512 count=1024
1024+0 records in
1024+0 records out
524288 bytes (524 kB) copied, 0.0385181 s, 13.6 MB/s
[root@localhost ~]# kpartx -a /dev/vdb
Warning: Disk has a valid GPT signature but invalid PMBR.
Assuming this disk is *not* a GPT disk anymore.
Use gpt kernel option to override. Use GNU Parted to correct disk.
[root@localhost ~]# kpartx -a /dev/vdc
Warning: Disk has a valid GPT signature but invalid PMBR.
Assuming this disk is *not* a GPT disk anymore.
Use gpt kernel option to override. Use GNU Parted to correct disk.
[root@localhost ~]# cat /proc/mdstat
Personalities : [raid1]
unused devices: <none>
[root@localhost ~]# parted /dev/vdb -s mklabel gpt mkpart primary ext4
1M 200M mkpart primary ext4 200M 1224M mkpart primary ext4 1224M 100%
[root@localhost ~]# parted /dev/vdc -s mklabel gpt mkpart primary ext4
1M 200M mkpart primary ext4 200M 1224M mkpart primary ext4 1224M 100%
[root@localhost ~]# cat /proc/mdstat
Personalities : [raid1]
unused devices: <none>
[root@localhost ~]# cat /proc/mdstat
Personalities : [raid1]
md2 : active raid1 vdc3[1] vdb3[0]
19775360 blocks super 1.0 [2/2] [UU]
md1 : active raid1 vdb2[0]
999360 blocks super 1.0 [2/1] [U_]
md0 : active raid1 vdb1[0]
194496 blocks super 1.0 [2/1] [U_]
unused devices: <none>
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