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Eeqmcsq

Member

Registered: 2017-09-19

Posts: 52  

Re: [SOLVED] Should the live desktop auto start RAID arrays?

Here's what I've learned tonight about blacklisting that's not been mentioned in other comments.

* What it takes to unload the md_mod module

Running "sudo modprobe -r md_mod" returns the error: "modprobe: FATAL: Module md_mod is in use.". But it doesn't tell you who's using it.

Running "sudo rmmod md_mod" returns the error: "rmmod: ERROR: Module md_mod is in use by: raid1 raid10 raid0 raid456".

So the solution is:

- Stop all RAID arrays so that the raid modules can be unloaded:
  - sudo mdadm --stop /dev/mdx /dev/mdy, etc

- Remove the 4 raid modules, then md_mod.
  - sudo rmmod raid1 raid10 raid0 raid456 md_mod

* What if you blacklisted the raid modules

I modified /etc/modprobe.d/mdadm.conf and added these lines, then rebuilt the init ram disk, then rebooted.

blacklist raid1
blacklist raid10
blacklist raid0
blacklist raid456
blacklist md_mod

The result was that the RAID arrays block devices were STILL created, but are inactive. /proc/mdstat also shows no raid "personalities" available.

$ ls -l /dev/md*
brw-rw---- 1 root disk 9, 127 Aug 28 21:45 /dev/md127
brw-rw---- 1 root disk 9,  22 Aug 28 21:45 /dev/md22

$ cat /proc/mdstat 
Personalities : 
md22 : inactive sda1[1] sdc1[0]
      200705 blocks super 1.2
       
md127 : inactive sda2[1] sdc2[0]
      197953 blocks super 1.2
       
unused devices: <none>

Looking at the loaded modules "sudo lsmod | egrep 'raid|md' | sort", the md_mod is STILL loaded, but none of the raid modules were loaded. As mentioned by g4sra, blacklisting doesn't prevent other ways of loading the md_mod.

stargate-sg1-cheyenne-mtn

Member

Registered: 2023-11-27

Posts: 359  

Re: [SOLVED] Should the live desktop auto start RAID arrays?

thanks to everyone who is talented enough to continue to investigate "the borking"

hopefully a fix can be found

---

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fsmithred

Administrator

Registered: 2016-11-25

Posts: 2,692  

Re: [SOLVED] Should the live desktop auto start RAID arrays?

Yeah, I ran into that "module is in use" warning. I managed to screw up my builds yesterday so that the desktop wouldn't start, and I finally found my error this morning. Right now I'm leaning toward removing all the mdadm stuff from the live and letting people rely on the rescue functions in the netinstall iso. I think I'll make a no-raid iso for the main site and any other test isos can be uploaded to a different location.

I'm assuming that the netinstall gives you more control over assembling raid arrays, but I've only used it a couple of times and never looked into the code.

I'm still a little frazzled from yesterday. New iso(s) coming later today (probably).

Thanks for persevering.

fsmithred

Administrator

Registered: 2016-11-25

Posts: 2,692  

Re: [SOLVED] Should the live desktop auto start RAID arrays?

I think I found a simple solution. This iso does not have mdadm installed or have the config files for it. It does have the mdadm package sitting in the root of the filesystem, and it can easily be installed with sudo dpkg -i /mdadm*.deb. You don't need a network connection for this to work.
https://files.devuan.org/devuan_excalib … p-live.iso

Tested in vbox with a RAID1 with two virtual hard disks. I booted the iso with the drives attached, installed mdadm and was able to run mdadm commands. There was no active array until I assembled /dev/md0. Please confirm.

Eeqmcsq

Member

Registered: 2017-09-19

Posts: 52  

Re: [SOLVED] Should the live desktop auto start RAID arrays?

* Quick summary

@fsmithred - I tested the live desktop iso devuan_excalibur_6.0-noraid-2025-08-29_1719_amd64_desktop-live.iso, and I confirmed that it did NOT auto start my test RAID arrays, which is good. I also confirmed that I can install the mdadm.deb in the root directory and do some RAID stuff.

The next test is the REAL test: run the desktop live on the 2 PCs that I reported in the first comment and make sure there are no other hidden surprises. Of course, I'll have to first run backups on those two PCs, which means digging out some extra HDDs, USB to SATA dock, etc. from my closet of tech stuff. So it might take a few days before I have more test results.

* Test notes

* Checking the iso's /live/initrd.img
  - file: devuan_excalibur_6.0-noraid-2025-08-29_1719_amd64_desktop-live.iso
  - Steps: Mount the iso, copy live/initrd.img to a temp directory.
  - cmd: unmkinitramfs initrd.img <output directory>
  - Weird. Extracting the initrd.img produces 3 directories: early, early2, main. Since it works, this could be just the way the live desktop init ram disk is organized.
  - Inside main, the contents look like the usual init ram disk.
  - find . | grep mdadm : No files found. Nothing related to mdadm is inside this ramdisk.
  - find . | grep rules.d : None of the rules files in udev/rules.d have any relation to md or raid.

Conclusion so far: If the init ram disk is has no knowledge of RAID, it shouldn't auto start any of my test RAID arrays.

* Checking the live desktop
  - cat /proc/mdstat  : file not found
  - sudo which mdadm  : file not found
  - lsmod | grep raid : No raid0, raid1, etc. modules.
  - lsmod | grep md   : No md_mod module.

Conclusion so far: Now that's what I call a solution. As predicted, since the init ram disk is totally clueless about RAID, it didn't (or couldn't) auto start any of the RAID arrays.

* Live desktop: installing mdadm.deb located on the root directory
  - install cmd: sudo dpkg -i /mdadm_4.4-11devuan3_amd64.deb
    - The install worked. There were some info messages about "live system is running on read-only media", and an error with grub-probe, but I'll see how far I can get.
  - Checking lsmod, md_mod is now loaded, but none of the raid modules are loaded.
  - cat /proc/mdstat: File exists. No RAID personalities listed. No arrays started.
  - sudo mdadm --examine --scan
    - Correctly discovered two RAID arrays, /dev/md/11, dev/md/22.
      - I don't know what the extra / means between the "md" and the number, but I'll keep going.
  - sudo mdadm --assemble /dev/md77 --uuid=<RAID UUID>
    - Array started on the intentionally weird md number, md77.
    - Array is confirmed in /proc/mdstat.
    - /proc/mdstat also shows the "raid1" personality.
    - lsmod now shows that the raid1 module is loaded. I guess the raid modules get loaded when they're needed.
      - This is convenient. The user doesn't have to manually load specific RAID modules in order to start their RAID arrays.
  - sudo mdadm --stop /dev/md77
    - Unsurprisingly, this also works.

  + Retest with no network connection (unplug from the PC).
    - Results: all same

  + Retest with no internet connection (plug PC into LAN, but unplug router's WAN).
    - Results: all same

Conclusion: Confirmed that the user can install mdadm locally and do RAID stuff, and there's no dependency on an Internet connection or any LAN connection.