Há alguns erros estranhos aparecendo na minha saída dmesg relacionada à montagem sda4 na inicialização, que é uma partição estendida contendo volumes lógicos usados.
A seguir, uma extração da minha saída dmesg logo após a inicialização. Eu removi algumas [UFW BLOCK] entradas de firewall entre elas.
[ 842.165660] SGI XFS with ACLs, security attributes, realtime, no debug enabled
[ 842.372589] JFS: nTxBlock = 8192, nTxLock = 65536
[ 842.668365] ntfs: driver 2.1.32 [Flags: R/O MODULE].
[ 843.035074] QNX4 filesystem 0.2.3 registered.
[ 843.288031] raid6: sse2x1 gen() 2212 MB/s
[ 843.356052] raid6: sse2x1 xor() 1599 MB/s
[ 843.424044] raid6: sse2x2 gen() 3118 MB/s
[ 843.492027] raid6: sse2x2 xor() 1502 MB/s
[ 843.560047] raid6: sse2x4 gen() 2975 MB/s
[ 843.628024] raid6: sse2x4 xor() 1857 MB/s
[ 843.628034] raid6: using algorithm sse2x2 gen() 3118 MB/s
[ 843.628037] raid6: .... xor() 1502 MB/s, rmw enabled
[ 843.628041] raid6: using intx1 recovery algorithm
[ 843.660527] xor: measuring software checksum speed
[ 843.700031] prefetch64-sse: 3182.000 MB/sec
[ 843.740020] generic_sse: 3851.000 MB/sec
[ 843.740028] xor: using function: generic_sse (3851.000 MB/sec)
[ 843.869982] Btrfs loaded
[ 845.893662] EXT4-fs (sda4): unable to read superblock
[ 845.896625] EXT4-fs (sda4): unable to read superblock
[ 845.900337] EXT4-fs (sda4): unable to read superblock
[ 845.903455] FAT-fs (sda4): invalid media value (0xda)
[ 845.903464] FAT-fs (sda4): Can't find a valid FAT filesystem
[ 845.912432] XFS (sda4): Invalid superblock magic number
[ 845.919404] FAT-fs (sda4): invalid media value (0xda)
[ 845.919413] FAT-fs (sda4): Can't find a valid FAT filesystem
[ 845.927924] MINIX-fs: unable to read superblock
[ 846.001284] attempt to access beyond end of device
[ 846.001293] sda4: rw=16, want=3, limit=2
[ 846.001300] hfsplus: unable to find HFS+ superblock
[ 846.014902] qnx4: no qnx4 filesystem (no root dir).
[ 846.018195] 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
[ 846.024054] hfs: can't find a HFS filesystem on dev sda4
[ 890.554489] EXT4-fs (sda4): unable to read superblock
[ 890.557377] EXT4-fs (sda4): unable to read superblock
[ 890.560315] EXT4-fs (sda4): unable to read superblock
[ 890.563428] FAT-fs (sda4): invalid media value (0xda)
[ 890.563436] FAT-fs (sda4): Can't find a valid FAT filesystem
[ 890.573590] XFS (sda4): Invalid superblock magic number
[ 890.579829] FAT-fs (sda4): invalid media value (0xda)
[ 890.579838] FAT-fs (sda4): Can't find a valid FAT filesystem
[ 890.591160] MINIX-fs: unable to read superblock
[ 890.596813] attempt to access beyond end of device
[ 890.596837] sda4: rw=16, want=3, limit=2
[ 890.596876] hfsplus: unable to find HFS+ superblock
[ 890.601952] qnx4: no qnx4 filesystem (no root dir).
[ 890.607635] 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
[ 890.613446] hfs: can't find a HFS filesystem on dev sda4
[ 2111.590730] perf interrupt took too long (2505 > 2500), lowering kernel.perf_event_max_sample_rate to 50000
[ 2323.551898] EXT4-fs (sda4): unable to read superblock
[ 2323.555029] EXT4-fs (sda4): unable to read superblock
[ 2323.558560] EXT4-fs (sda4): unable to read superblock
[ 2323.561654] FAT-fs (sda4): invalid media value (0xda)
[ 2323.561662] FAT-fs (sda4): Can't find a valid FAT filesystem
[ 2323.570667] XFS (sda4): Invalid superblock magic number
[ 2323.577885] FAT-fs (sda4): invalid media value (0xda)
[ 2323.577893] FAT-fs (sda4): Can't find a valid FAT filesystem
[ 2323.588531] MINIX-fs: unable to read superblock
[ 2323.594927] attempt to access beyond end of device
[ 2323.594937] sda4: rw=16, want=3, limit=2
[ 2323.594943] hfsplus: unable to find HFS+ superblock
[ 2323.599796] qnx4: no qnx4 filesystem (no root dir).
[ 2323.603466] 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
[ 2323.627446] hfs: can't find a HFS filesystem on dev sda4
[ 2347.927763] EXT4-fs (sda4): unable to read superblock
[ 2347.937927] EXT4-fs (sda4): unable to read superblock
[ 2347.943278] EXT4-fs (sda4): unable to read superblock
[ 2347.954206] FAT-fs (sda4): invalid media value (0xda)
[ 2347.954217] FAT-fs (sda4): Can't find a valid FAT filesystem
[ 2348.020480] XFS (sda4): Invalid superblock magic number
[ 2348.049075] FAT-fs (sda4): invalid media value (0xda)
[ 2348.049085] FAT-fs (sda4): Can't find a valid FAT filesystem
[ 2348.062423] MINIX-fs: unable to read superblock
[ 2348.066949] attempt to access beyond end of device
[ 2348.066959] sda4: rw=16, want=3, limit=2
[ 2348.066965] hfsplus: unable to find HFS+ superblock
[ 2348.071702] qnx4: no qnx4 filesystem (no root dir).
[ 2348.076214] 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
[ 2348.095021] hfs: can't find a HFS filesystem on dev sda4
Mais algumas informações sobre o meu sistema (Ubuntu 15.10 64 bits) e partições:
Saída de lsblk /dev/sda :
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 232,9G 0 disk
├─sda1 8:1 0 100M 0 part /win/boot
├─sda2 8:2 0 74G 0 part /win/c
├─sda3 8:3 0 8G 0 part /boot
├─sda4 8:4 0 1K 0 part
├─sda5 8:5 0 31,3G 0 part /images
├─sda6 8:6 0 40G 0 part /
├─sda7 8:7 0 60G 0 part /home
├─sda8 8:8 0 15G 0 part /win/share
└─sda9 8:9 0 4,6G 0 part [SWAP]
Saída de sudo parted -l /dev/sda :
Model: ATA Hitachi HDS72102 (scsi)
Disk /dev/sda: 250GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos
Disk Flags:
Number Start End Size Type File system Flags
1 1049kB 106MB 105MB primary ntfs boot
2 106MB 79,6GB 79,4GB primary ntfs
3 79,6GB 88,1GB 8590MB primary ext4
4 88,1GB 250GB 162GB extended
6 88,1GB 131GB 42,9GB logical ext4
7 131GB 196GB 64,4GB logical ext4
8 196GB 212GB 16,1GB logical fat32
9 212GB 217GB 4876MB logical linux-swap(v1)
5 217GB 250GB 33,6GB logical ext4
Saída de mount | grep /dev/sda :
/dev/sda6 on / type ext4 (rw,relatime,errors=remount-ro,data=ordered)
/dev/sda1 on /win/boot type fuseblk (rw,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096)
/dev/sda2 on /win/c type fuseblk (rw,relatime,user_id=0,group_id=0,default_permissions,allow_other,blksize=4096)
/dev/sda7 on /home type ext4 (rw,relatime,data=ordered)
/dev/sda5 on /images type ext4 (rw,relatime,data=ordered)
/dev/sda3 on /boot type ext4 (rw,relatime,data=ordered)
/dev/sda8 on /win/share type vfat (rw,relatime,gid=46,fmask=0007,dmask=0007,allow_utime=0020,codepage=437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro)
Conteúdo de /etc/fstab :
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point> <type> <options> <dump> <pass>
# / was on /dev/sda6 during installation
UUID=eee18451-b607-4875-8a88-c9cb6c6544c8 / ext4 errors=remount-ro 0 1
# /boot was on /dev/sda3 during installation
UUID=6dbb8633-dadd-4b5e-8d85-b0895fde9dfb /boot ext4 defaults 0 2
# /home was on /dev/sda7 during installation
UUID=485b3ef1-7216-4053-b25c-f656d529e8e6 /home ext4 defaults 0 2
# /images was on /dev/sda5 during installation
UUID=81dc42c4-a161-4ccd-b704-6e5c09298943 /images ext4 defaults 0 2
# /old partition image file of previous 15.04 installation
/images/backup/ubuntu-vivid-151028-ext4.img /old ext4 defaults,ro
# /win/boot was on /dev/sda1 during installation
UUID=90DCF3A5DCF3842E /win/boot ntfs defaults,umask=007,gid=46 0 0
# /win/c was on /dev/sda2 during installation
UUID=482C7A572C7A3FCC /win/c ntfs defaults,umask=007,gid=46 0 0
# /win/share was on /dev/sda8 during installation
UUID=B148-49F9 /win/share vfat utf8,umask=007,gid=46 0 1
# swap was on /dev/sda9 during installation
UUID=4b184fdc-fe7a-4019-92e4-8a6607fe7291 none swap sw 0 0
/dev/fd0 /media/floppy0 auto rw,user,noauto,exec,utf8 0 0
Isso pode ser tarde, mas eu encontrei um bug debian: link
Parece que o os-prober é o problema e é executado quando um novo kernel é instalado. Acabei de testar uma atualização em um sistema que não tinha essas entradas na saída dmesg antes da atualização, mas elas apareceram depois.