os-prober tries to mount bios_grub (BIOS boot) partition

[Götz Christ]

After a kernel update, update-grub is triggered and calls os-prober, which tries to mount a BIOS boot or bios_grub partition, this

[ 4207.126455] SGI XFS with ACLs, security attributes, realtime, no debug enabled
[ 4207.179019] JFS: nTxBlock = 8192, nTxLock = 65536
[ 4207.237139] ntfs: driver 2.1.32 [Flags: R/O MODULE].
[ 4207.312000] QNX4 filesystem 0.2.3 registered.
[ 4207.504556] EXT4-fs (sda1): VFS: Can't find ext4 filesystem
[ 4207.508148] EXT4-fs (sda1): VFS: Can't find ext4 filesystem
[ 4207.511768] EXT4-fs (sda1): VFS: Can't find ext4 filesystem
[ 4207.516335] squashfs: SQUASHFS error: Can't find a SQUASHFS superblock on sda1
[ 4207.520951] FAT-fs (sda1): invalid media value (0x7d)
[ 4207.520962] FAT-fs (sda1): Can't find a valid FAT filesystem
[ 4207.537370] XFS (sda1): Invalid superblock magic number
[ 4207.572688] FAT-fs (sda1): invalid media value (0x7d)
[ 4207.572699] FAT-fs (sda1): Can't find a valid FAT filesystem
[ 4207.582957] VFS: Can't find a Minix filesystem V1 | V2 | V3 on device sda1.
[ 4207.605925] hfsplus: unable to find HFS+ superblock
[ 4207.613271] qnx4: no qnx4 filesystem (no root dir).
[ 4207.617614] ufs: You didn't specify the type of your ufs filesystem

               mount -t ufs -o ufstype=sun|sunx86|44bsd|ufs2|5xbsd|old|hp|nextstep|nextstep-cd|openstep ...

               >>>WARNING<<< Wrong ufstype may corrupt your filesystem, default is ufstype=old
[ 4207.617978] ufs: ufs_fill_super(): bad magic number
[ 4207.622340] hfs: can't find a HFS filesystem on dev sda1

A similar patch[1] like the one added in bug 1374759 could fix this, but for the corresponding partition type.

[1] https://launchpadlibrarian.net/247090905/skip-msdos-extpart-sooner.debdiff

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: os-prober 1.70ubuntu3
ProcVersionSignature: Ubuntu 4.4.0-36.55-generic 4.4.16
Uname: Linux 4.4.0-36-generic i686
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: i386
Date: Mon Sep 19 15:16:42 2016
Dependencies:
 gcc-6-base 6.0.1-0ubuntu1
 libc6 2.23-0ubuntu3
 libgcc1 1:6.0.1-0ubuntu1
InstallationDate: Installed on 2016-09-18 (1 days ago)
InstallationMedia: Ubuntu-MATE 16.04.1 LTS "Xenial Xerus" - Release i386 (20160719)
SourcePackage: os-prober
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Brian Martin (7-launchpad-9)]

My parted output for this partition is:

Number Start End Size File system Name Flags
 1 1049kB 8389kB 7340kB bios_grub bios_grub

Ideally, the bios_grub flag could be used to tell relevant code (os-prober, apparently) to ignore this partition. That would eliminate 96 scary messages from my boot log. There are two disks on my system (for failover purposes), each with a bios_grub flag. Each one gets 48 of these useless messages. For some reason, os-prober is probing each disk multiple times. Since I monitor my logs closely, I'd love to have these go away. Log messages for one of the two disks appears below, just in case there's some new information in them.

---

> Dec 21 05:26:46 samantha kernel: [1024918.757361] EXT4-fs (sda1): VFS: Can't find ext4 filesystem
-> Dec 21 05:26:46 samantha kernel: [1024918.762203] EXT4-fs (sda1): VFS: Can't find ext4 filesystem
-> Dec 21 05:26:46 samantha kernel: [1024918.767102] EXT4-fs (sda1): VFS: Can't find ext4 filesystem
-> Dec 21 05:26:46 samantha kernel: [1024918.771882] squashfs: SQUASHFS error: Can't find a SQUASHFS superblock on sda1
-> Dec 21 05:26:46 samantha kernel: [1024918.776705] FAT-fs (sda1): invalid media value (0x7d)
-> Dec 21 05:26:46 samantha kernel: [1024918.776803] FAT-fs (sda1): Can't find a valid FAT filesystem
-> Dec 21 05:26:46 samantha kernel: [1024918.791838] XFS (sda1): Invalid superblock magic number
-> Dec 21 05:26:46 samantha kernel: [1024918.801632] FAT-fs (sda1): invalid media value (0x7d)
-> Dec 21 05:26:46 samantha kernel: [1024918.801730] FAT-fs (sda1): Can't find a valid FAT filesystem
-> Dec 21 05:26:46 samantha kernel: [1024918.815672] VFS: Can't find a Minix filesystem V1 | V2 | V3 on device sda1.
-> Dec 21 05:26:47 samantha kernel: [1024918.843397] hfsplus: unable to find HFS+ superblock
-> Dec 21 05:26:47 samantha kernel: [1024918.848163] qnx4: no qnx4 filesystem (no root dir).
-> Dec 21 05:26:47 samantha kernel: [1024918.852787] ufs: You didn't specify the type of your ufs filesystem
-> Dec 21 05:26:47 samantha kernel: [1024918.852787] mount -t ufs -o ufstype=sun|sunx86|44bsd|ufs2|5xbsd|old|hp|nextstep|nextstep-cd|openstep ...
-> Dec 21 05:26:47 samantha kernel: [1024918.852787] >>>WARNING<<< Wrong ufstype may corrupt your filesystem, default is ufstype=old
-> Dec 21 05:26:47 samantha kernel: [1024918.853511] ufs: ufs_fill_super(): bad magic number
-> Dec 21 05:26:47 samantha kernel: [1024918.863201] hfs: can't find a HFS filesystem on dev sda1
-> Dec 21 05:26:47 samantha kernel: [1024919.062796] EXT4-fs (sdb1): VFS: Can't find ext4 filesystem
-> Dec 21 05:26:47 samantha kernel: [1024919.067520] EXT4-fs (sdb1): VFS: Can't find ext4 filesystem
-> Dec 21 05:26:47 samantha kernel: [1024919.072411] EXT4-fs (sdb1): VFS: Can't find ext4 filesystem
-> Dec 21 05:26:47 samantha kernel: [1024919.077055] squashfs: SQUASHFS error: Can't find a SQUASHFS superblock on sdb1
-> Dec 21 05:26:47 samantha kernel: [1024919.081806] FAT-fs (sdb1): invalid media value (0x7d)
-> Dec 21 05:26:47 samantha kernel: [1024919.081904] FAT-fs (sdb1): Can't find a valid FAT filesystem
-> Dec 21 05:26:47 samantha kernel: [1024919.097725] XFS (sdb1): Inval...