Bug 51220

Summary:	RFE: systemd should be able to do minimal MD disassembly on shutdown
Product:	systemd	Reporter:	Anonymous Helper <anonymous>
Component:	general	Assignee:	systemd-bugs
Status:	NEW ---	QA Contact:	systemd-bugs
Severity:	normal
Priority:	medium
Version:	unspecified
Hardware:	All
OS:	Linux (All)
Whiteboard:
i915 platform:		i915 features:

Description Anonymous Helper 2012-06-18 23:12:53 UTC

lsblk:
NAME        MAJ:MIN RM   SIZE RO TYPE   MOUNTPOINT
sda           8:0    0 698,7G  0 disk   
├─sda1        8:1    0    65M  0 part   /boot
├─sda2        8:2    0     4M  0 part   
├─sda3        8:3    0    80M  0 part   
│ └─md0       9:0    0    84M  0 linear 
│   └─md0p1 259:0    0    80M  0 md     
├─sda4        8:4    0   4,1G  0 part   [SWAP]
├─sda5        8:5    0    13G  0 part   /
└─sda6        8:6    0   678G  0 part   /home
sr0          11:0    1  1024M  0 rom    
loop0         7:0    0     4M  0 loop   
└─md0         9:0    0    84M  0 linear 
  └─md0p1   259:0    0    80M  0 md     

This setup is to enable me to access /dev/sda3 from within QEMU. loop0 points to an image file containing MBR, on the /home partition. Sometimes when I shutdown I forget to disassemble the md0 device, and systemd fails to do so automatically; on next boot, some file systems need to recover from their journals. A bit annoying.

Apparently block-device dependency information like this is available to lsblk, and losetup -a will reveal which file a loop device points to. systemd could probably also make use of that.

Comment 1 Kay Sievers 2012-06-19 02:40:29 UTC

Systemd does not support "fake block devices". This needs to be provided by
the raid tools themselves and hook up into systemd.

Most of the things are done today by (mostly weird) shell scrips provided
by the distributions. Systemd has currently no plans to support MD or LVM
natively.

We provide minimal dis-assembly support for device-mapper volumes, something
similar could probably be done for MD, but someone needs to do it, and it
would need to be reasonable simple and not involve running daemons, calling-out
to command line tools or linking against uncommon libraries.

None of the main systemd developers I know uses any MD or LVM, so I have no
idea who we could expect to do that.

Comment 2 Zbigniew Jedrzejewski-Szmek 2014-06-26 03:34:48 UTC

During shutdown systemd (actually the shutdown binary) will attempt to destroy DM devices and loop devices, and unmount filesystems. So I'd think it should deal with this setup. Is this still a problem?

Comment 3 Lennart Poettering 2014-06-26 17:26:13 UTC

(In reply to comment #2)
> During shutdown systemd (actually the shutdown binary) will attempt to
> destroy DM devices and loop devices, and unmount filesystems. So I'd think
> it should deal with this setup. Is this still a problem?

Well, MD is not DM. And given that we detach all that stuff, I'd be open to adding a patch that does what we do for DM also for MD...

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