Diskfilter writes are not supported > What triggers this error?


RAID and LVM users may run into a cryptic warning on boot from GRUB; because some variants of RAID and LVM are not supported for writing by GRUB itself. GRUB would typically try to write a tiny file to the boot partition for things like remembering the last selected boot entry.

[Test Case]
On an affected system (typically any RAID/LVM setup where the boot device is on RAID or on a LVM device), try to boot. Without the patch, the message will appear, otherwise it will not.

[Regression Potential]
The potential for regression is minimal as the patch involves enforcing the fact that diskfilter writes are unsupported by grub in menu building scripts, which will automatically avoid enabling recordfail (the offending feature which saves GRUB's state) if the boot partition is detected to be on a device which does not support diskfilter writes.


Once grub chooses what to boot to, an error shows up and will sit on the screen for approx....

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A couple of days ago I installed a new test VM with Ubuntu 14.04.2 in my home LAN running in VMware player. An error appeared during boot:

error: diskfilter writes are not supported.
Press any key to continue...

As it was a test VM and I only needed the VM for a short time, I didn't really look that error up. But yesterday I installed a new production VM at work on ESX and hit the same error.

A quick research points me to the AskUbuntu entry #468466 and to the Ubuntu bug #1274320, a grub2 bug reported at the end of January 2014. On the AskUbuntu site, there is an excellent response why this bug happens by Rarylson Freitas.

The partition setup of this VM has the root (/) partition loaded from a logical volume, which seems to trigger this bug.

As this is a new VM, I decided to reinstall Ubuntu and to create a primary partition for the root partition. Ubuntu now boots correct without errors.

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Hi all, I have installed grub-customizer to change grub2 resolution, but after having saved the customization and reboot, the system wait 10 seconds at the ASUS power on logo, nothing has changed in grub 2 and after choosing the partition to boot it tells me and error message: Error: diskfilter writes are not supported. I have read some people pressed the button Install in MBR in the file menu of grub customizer, but i do not know what it does, so i do not want to go for a try and error step. What does MBR stand for? How can i Use it properly? I read also that the bug has something to do with RAID, but i do not have any. My system is: Intel i7-2670QM; RAM 8Gb SSD Patriot Blast 240 Gb, 60 Gb Home Partition, 60 Gb root Fedora 23 partition; 120 gb Windows 10 Partition.

Thank you for support...

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Created attachment 795965 [details] photo of bootscreen after upgrade to F19 GRUB2 comes up with "error: diskfilter writes are not supported" and waits some seconds to press a key and thanks god boots after that automatically to not break wakeup-on-lan (see also attachment) but what is this nonsense? Personalities : [raid1] [raid10] md2 : active raid10 sda3[0] sdc3[1] sdb3[3] sdd3[2] 3875222528 blocks super 1.1 512K chunks 2 near-copies [4/4] [UUUU] bitmap: 2/29 pages [8KB], 65536KB chunk md1 : active raid10 sda2[0] sdc2[1] sdb2[3] sdd2[2] 30716928 blocks super 1.1 512K chunks 2 near-copies [4/4] [UUUU] bitmap: 0/1 pages [0KB], 65536KB chunk md0 : active raid1 sda1[0] sdc1[1] sdd1[2] sdb1[3] 511988 blocks super 1.0 [4/4] [UUUU] unused devices: _________________________________________________ [root@rh:~]$ cat /boot/grub2/grub.cfg # # DO NOT EDIT THIS FILE # # It is automatically generated by grub2-mkconfig using templates # from /etc/grub.d and settings from...
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