grub2 stopped working: another 'Kernel Panic - not syncing'

[MikZ]

G'day people,

I rebooted my Mint 14 system for the first time in weeks, and the following error came up after I selected Mint from the grub menu.

I've seen similar errors in the forums, but none of those solutions worked, and neither have the educated guesses I've made along the way—see below. I'd appreciate advice on what to try next.

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[    0.360231] Kernel Panic - not syncing: VFS : Unable to mount root fs on unknown-block(0,0)
[    0.360260] Pid: 1, comm: swapper/0 Not tainted 3.5.0-27-generic #46-Ubuntu
[    0.360283] Call Trace:
[    0.360304] [ffffffff81674200] panic+0xba/0x1c9
[    0.360328] [ffffffff81cf3062] mount_block_root+0x1d6/0x287
[    0.360352] [ffffffff81cf32ac] mount_root+0x57/0x5b
[    0.360375] [ffffffff81cf341d] prepare_namespace+0x16d/0x1a6
[    0.360400] [ffffffff8107d0b0] ? release_tgcred.isra.7+0x30/0x30
[    0.360423] [ffffffff81cf2dc8] kernel_init+0x1c4/0x1c9
[    0.360446] [ffffffff81cf2588] ? loglevel+0x31/0x31
[    0.360468] [ffffffff8168ad64] kernel_threat_helper+0x4/0x10
[    0.360491] [ffffffff81cf2c04] ? start_kernel+0x3c4/0x3c4
[    0.360514] [ffffffff8168ad60] ? gs_change+0x13/0x13

I've tried reinstalling grub from a live CD:

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sudo grub-install --root-directory=/media/target --boot-directory=/media/target/boot /dev/sdb

Yes, those directories are right—I mounted them myself and can ls them, etc. I'm pretty sure the device is correct; the relevant /boot partition is on /dev/sdb for historical reasons that I also discuss below, even though Mint's root directory is on /dev/sda. In any case, the error persisted.

One thing I noticed is that grub seems to call /dev/sdb hd1 in the menu, but hd0 at the grub command line. To illustrate, here's what I found at the grub command line:

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grub> ls (hd0,gpt6)
	Partition hd0,gpt6: Filesystem type ext* - Last modification time 2013-05-04 03:23:32 Saturday, UUID ced816a2-0bd1-4c7a-b43a-92cc57cffa6e - Partition start at 1884977152 - Total size 393216 sectors
grub> ls (hd0,gpt6)/
lost+found/ grub/ System.map-3.5.0-17-generic abi-3.5.0-17-generic config-3.5.0-17-generic initrd.img-3.5.0-17-generic memtest86+.bin memtest86+_multiboot.bin vmlinuz-3.5.0-17-generic System.map-3.5.0-27-generic config-3.5.0-27-generic vmlinuz-3.5.0-27-generic vmlinuz-3.5.0-27-generic vmlinuz-3.5.0-27-generic.efi.signed initrd.img-3.5.0-27-generic
grub> ls (hd0,gpt6)/boot/grub
error: file `/boot/grub' not found.
grub> ls (hd0,gpt6)/grub
gfxblacklist.txt i386-pc/ locale/ fonts/ grub.cfg grubenv

... but when I type e at the boot menu, it looks like this:

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	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_gpt
	insmod ext2
	set root='hd1,gpt6'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6  ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	else
	  search --no-floppy --fs-uuid --set=root ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	fi
	linux	/vmlinuz-3.5.0-27-generic.efi.signed root=/dev/sda8 ro   quiet splash elevator=deadline $vt_handoff

Nevertheless, when I changed the three hd1s to hd0, I still get the same error. (The clock times in the leading square brackets on each line are different, of course, but nothing else.) Ditto when I also change ahci1 to ahci0.

I've seen a post or two where the error appeared after a new Mint installation, or after a kernal update like in http://askubuntu.com/questions/116635/k ... oo-swapper. I've always thought kernel updates come with full-blown distro upgrades, and not just the routine software updates I've done, but maybe I'm wrong. I suppose my unorthodox setup might have confused some update script, though. In any case, I haven't tried the update-initramfs command in the post I linked to, because it's a year old, and not Mint—I don't want to unwittingly create some kind of dependency conflict on top of it all. But if somebody knowledgeable here could assure me it's a safe thing to try, I'm all for it.

Below is the output from bootinfoscript. The first thing it says is that grub's on the MBR of both of my drives, but it's the /dev/sdb bootloader that I boot to—the one on /dev/sda never worked, and my setup is my workaround for the fact that Mint 14 and Windows 8 don't seem to like booting off a SSD together. I have my BIOS boot /dev/sdb by default, and I interrupt it and tell it to boot /dev/sda instead on the odd occasion I want Windows. (I don't think grub ever booted Windows properly on my machine, but it never bothered me enough for me to investigate.)

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                  Boot Info Script 0.61      [1 April 2012]


============================= Boot Info Summary: ===============================

 => Grub2 (v1.99) is installed in the MBR of /dev/sda and looks at sector 
    133847040 of the same hard drive for core.img, but core.img can not be 
    found at this location.
 => Grub2 (v1.99) is installed in the MBR of /dev/sdb and looks at sector 
    1885370368 of the same hard drive for core.img. core.img is at this 
    location and looks in partition 72 for .

sda1: __________________________________________________________________________

    File system:       ntfs
    Boot sector type:  Windows Vista/7: NTFS
    Boot sector info:  No errors found in the Boot Parameter Block.
    Operating System:  
    Boot files:        

sda2: __________________________________________________________________________

    File system:       vfat
    Boot sector type:  Unknown
    Boot sector info:  No errors found in the Boot Parameter Block.
    Operating System:  
    Boot files:        /efi/Boot/bootx64.efi

sda3: __________________________________________________________________________

    File system:       
    Boot sector type:  -
    Boot sector info: 
    Mounting failed:   mount: unknown filesystem type ''

sda4: __________________________________________________________________________

    File system:       ntfs
    Boot sector type:  Windows Vista/7: NTFS
    Boot sector info:  No errors found in the Boot Parameter Block.
    Operating System:  
    Boot files:        /bootmgr /Boot/BCD /Windows/System32/winload.exe

sda5: __________________________________________________________________________

    File system:       
    Boot sector type:  -
    Boot sector info: 
    Mounting failed:   mount: unknown filesystem type ''
mount: unknown filesystem type ''

sda6: __________________________________________________________________________

    File system:       ext4
    Boot sector type:  -
    Boot sector info: 
    Operating System:  
    Boot files:        

sda7: __________________________________________________________________________

    File system:       ext4
    Boot sector type:  -
    Boot sector info: 
    Operating System:  
    Boot files:        

sda8: __________________________________________________________________________

    File system:       ext4
    Boot sector type:  -
    Boot sector info: 
    Operating System:  Linux Mint 14 Nadia
    Boot files:        /etc/fstab

sdb1: __________________________________________________________________________

    File system:       ext4
    Boot sector type:  -
    Boot sector info: 
    Operating System:  
    Boot files:        

sdb2: __________________________________________________________________________

    File system:       ext4
    Boot sector type:  -
    Boot sector info: 
    Operating System:  
    Boot files:        

sdb3: __________________________________________________________________________

    File system:       
    Boot sector type:  -
    Boot sector info: 
    Mounting failed:   mount: unknown filesystem type ''
mount: unknown filesystem type ''
mount: unknown filesystem type ''

sdb4: __________________________________________________________________________

    File system:       ext4
    Boot sector type:  -
    Boot sector info: 
    Operating System:  
    Boot files:        

sdb5: __________________________________________________________________________

    File system:       ntfs
    Boot sector type:  Windows Vista/7: NTFS
    Boot sector info:  No errors found in the Boot Parameter Block.
    Operating System:  
    Boot files:        

sdb6: __________________________________________________________________________

    File system:       ext4
    Boot sector type:  -
    Boot sector info: 
    Operating System:  
    Boot files:        /grub/grub.cfg

sdb7: __________________________________________________________________________

    File system:       BIOS Boot partition
    Boot sector type:  Grub2's core.img
    Boot sector info: 

sdb8: __________________________________________________________________________

    File system:       ext3
    Boot sector type:  -
    Boot sector info: 
    Operating System:  
    Boot files:        

============================ Drive/Partition Info: =============================

Drive: sda _____________________________________________________________________

Disk /dev/sda: 256.1 GB, 256060514304 bytes
255 heads, 63 sectors/track, 31130 cylinders, total 500118192 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes

Partition  Boot  Start Sector    End Sector  # of Sectors  Id System

/dev/sda1                   1   500,118,191   500,118,191  ee GPT


GUID Partition Table detected.

Partition    Start Sector    End Sector  # of Sectors System
/dev/sda1           2,048     2,050,047     2,048,000 Windows Recovery Environment (Windows)
/dev/sda2       2,050,048     2,582,527       532,480 EFI System partition
/dev/sda3       2,582,528     2,844,671       262,144 Microsoft Reserved Partition (Windows)
/dev/sda4       2,844,672   137,056,255   134,211,584 Data partition (Windows/Linux)
/dev/sda5     485,437,440   500,117,503    14,680,064 -
/dev/sda6     137,056,256   137,449,471       393,216 Data partition (Windows/Linux)
/dev/sda7     137,449,472   138,498,047     1,048,576 Data partition (Windows/Linux)
/dev/sda8     138,498,048   485,435,548   346,937,501 Data partition (Windows/Linux)

Drive: sdb _____________________________________________________________________

Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders, total 1953525168 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 4096 bytes

Partition  Boot  Start Sector    End Sector  # of Sectors  Id System

/dev/sdb1                   1 1,953,525,167 1,953,525,167  ee GPT


GUID Partition Table detected.

Partition    Start Sector    End Sector  # of Sectors System
/dev/sdb1           2,048     8,390,655     8,388,608 Data partition (Windows/Linux)
/dev/sdb2       8,390,656    41,945,087    33,554,432 Data partition (Windows/Linux)
/dev/sdb3      41,945,088    57,691,181    15,746,094 Swap partition (Linux)
/dev/sdb4     104,921,088 1,616,541,695 1,511,620,608 Data partition (Windows/Linux)
/dev/sdb5   1,616,541,696 1,884,977,151   268,435,456 Data partition (Windows/Linux)
/dev/sdb6   1,884,977,152 1,885,370,367       393,216 Data partition (Windows/Linux)
/dev/sdb7   1,885,370,368 1,886,417,243     1,046,876 BIOS Boot partition
/dev/sdb8   1,886,418,944 1,953,523,711    67,104,768 Data partition (Windows/Linux)

"blkid" output: ________________________________________________________________

Device           UUID                                   TYPE       LABEL

/dev/loop0                                              squashfs   
/dev/sda1        A4645B9B645B6ED4                       ntfs       WINRE_DRV
/dev/sda2        D05C-66B8                              vfat       SYSTEM_DRV
/dev/sda4        DA885EE2885EBD27                       ntfs       Windows8_OS
/dev/sda6        6d3c351e-57cf-4a8f-90af-ef750044c636   ext4       
/dev/sda7        ea9d8614-05af-4e1a-954e-9e29be23e519   ext4       
/dev/sda8        39777fa9-0bb7-4301-ac98-379f12fd1bfb   ext4       
/dev/sdb1        468828a8-ee42-44e8-8b8b-fae6be2bd053   ext4       
/dev/sdb2        7133fea1-f360-492a-89c4-45ae79780e05   ext4       
/dev/sdb4        7e9d8cb4-846f-4034-b16e-77811ec1cb02   ext4       
/dev/sdb5        63D593D3565C55A6                       ntfs       /media/win/d
/dev/sdb6        ced816a2-0bd1-4c7a-b43a-92cc57cffa6e   ext4       
/dev/sdb8        afc6a4cb-4cba-43be-8700-ffd6e1e7040b   ext3       
/dev/sr0                                                iso9660    Linux Mint 14 Cinnamon 64-bit

================================ Mount points: =================================

Device           Mount_Point              Type       Options

/dev/loop0       /rofs                    squashfs   (ro,noatime)
/dev/sr0         /cdrom                   iso9660    (ro,noatime)


=============================== sda8/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>
proc            /proc           proc    nodev,noexec,nosuid 0       0
# / was on /dev/sda8 during installation
UUID=39777fa9-0bb7-4301-ac98-379f12fd1bfb /               ext4    errors=remount-ro,noatime,nodiratime,discard 0       1
# /boot was on /dev/sdb6 during installation
UUID=ced816a2-0bd1-4c7a-b43a-92cc57cffa6e /boot           ext4    defaults        0       2
# /home was on /dev/sdb8 during installation
UUID=afc6a4cb-4cba-43be-8700-ffd6e1e7040b /home           ext3    defaults        0       2
# /home/mikz was on /dev/sdb4 during installation
UUID=7e9d8cb4-846f-4034-b16e-77811ec1cb02 /home/mikz      ext4    defaults        0       2
# /media/win/c was on /dev/sda4 during installation
UUID=DA885EE2885EBD27 /media/win/c    ntfs    defaults,umask=007,gid=46,noatime,nodiratime,discard 0       0
# /media/win/d was on /dev/sdb5 during installation
UUID=63D593D3565C55A6 /media/win/d    ntfs    defaults,umask=007,gid=46 0       0
# /reserve/biosgrub was on /dev/sda7 during installation
UUID=ea9d8614-05af-4e1a-954e-9e29be23e519 /reserve/biosgrub ext4    defaults,noatime,nodiratime,discard        0       2
# /reserve/boot was on /dev/sda6 during installation
UUID=6d3c351e-57cf-4a8f-90af-ef750044c636 /reserve/boot   ext4    defaults,noatime,nodiratime,discard        0       2
# /tmp was on /dev/sdb2 during installation
UUID=7133fea1-f360-492a-89c4-45ae79780e05 /tmp            ext4    defaults        0       2
# /var was on /dev/sdb1 during installation
UUID=468828a8-ee42-44e8-8b8b-fae6be2bd053 /var            ext4    defaults        0       2
# swap was on /dev/sdb3 during installation
#UUID=3c58d06a-bb2c-4be4-a0d2-9db7439ac934 none            swap    sw              0       0
/dev/mapper/cryptswap1 none swap sw 0 0
--------------------------------------------------------------------------------

============================= sdb6/grub/grub.cfg: ==============================

--------------------------------------------------------------------------------
#
# DO NOT EDIT THIS FILE
#
# It is automatically generated by grub-mkconfig using templates
# from /etc/grub.d and settings from /etc/default/grub
#

### BEGIN /etc/grub.d/00_header ###
if [ -s $prefix/grubenv ]; then
  set have_grubenv=true
  load_env
fi
set default="0"

if [ x"${feature_menuentry_id}" = xy ]; then
  menuentry_id_option="--id"
else
  menuentry_id_option=""
fi

export menuentry_id_option

if [ "${prev_saved_entry}" ]; then
  set saved_entry="${prev_saved_entry}"
  save_env saved_entry
  set prev_saved_entry=
  save_env prev_saved_entry
  set boot_once=true
fi

function savedefault {
  if [ -z "${boot_once}" ]; then
    saved_entry="${chosen}"
    save_env saved_entry
  fi
}

function recordfail {
  set recordfail=1
  if [ -n "${have_grubenv}" ]; then if [ -z "${boot_once}" ]; then save_env recordfail; fi; fi
}

function load_video {
  if [ x$feature_all_video_module = xy ]; then
    insmod all_video
  else
    insmod efi_gop
    insmod efi_uga
    insmod ieee1275_fb
    insmod vbe
    insmod vga
    insmod video_bochs
    insmod video_cirrus
  fi
}

if [ x$feature_default_font_path = xy ] ; then
   font=unicode
else
insmod part_gpt
insmod ext2
set root='hd0,gpt8'
if [ x$feature_platform_search_hint = xy ]; then
  search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt8 --hint-efi=hd0,gpt8 --hint-baremetal=ahci0,gpt8  39777fa9-0bb7-4301-ac98-379f12fd1bfb
else
  search --no-floppy --fs-uuid --set=root 39777fa9-0bb7-4301-ac98-379f12fd1bfb
fi
    font="/usr/share/grub/unicode.pf2"
fi

if loadfont $font ; then
  set gfxmode=auto
  load_video
  insmod gfxterm
  set locale_dir=$prefix/locale
  set lang=en_AU
  insmod gettext
fi
terminal_output gfxterm
if [ "${recordfail}" = 1 ]; then
  set timeout=-1
else
  set timeout=10
fi
### END /etc/grub.d/00_header ###

### BEGIN /etc/grub.d/05_debian_theme ###
set menu_color_normal=white/black
set menu_color_highlight=black/light-gray
### END /etc/grub.d/05_debian_theme ###

### BEGIN /etc/grub.d/06_mint_theme ###
set menu_color_normal=white/black
set menu_color_highlight=white/light-gray
### END /etc/grub.d/06_mint_theme ###

### BEGIN /etc/grub.d/10_linux ###
function gfxmode {
	set gfxpayload="$1"
	if [ "$1" = "keep" ]; then
		set vt_handoff=vt.handoff=7
	else
		set vt_handoff=
	fi
}
if [ ${recordfail} != 1 ]; then
  if [ -e ${prefix}/gfxblacklist.txt ]; then
    if hwmatch ${prefix}/gfxblacklist.txt 3; then
      if [ ${match} = 0 ]; then
        set linux_gfx_mode=keep
      else
        set linux_gfx_mode=text
      fi
    else
      set linux_gfx_mode=text
    fi
  else
    set linux_gfx_mode=keep
  fi
else
  set linux_gfx_mode=text
fi
export linux_gfx_mode
if [ "$linux_gfx_mode" != "text" ]; then load_video; fi
menuentry 'Linux Mint 14 Cinnamon 64-bit, 3.5.0-27-generic.efi.signed (/dev/sdb6)' --class linuxmint --class gnu-linux --class gnu --class os {
	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_gpt
	insmod ext2
	set root='hd1,gpt6'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6  ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	else
	  search --no-floppy --fs-uuid --set=root ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	fi
	linux	/vmlinuz-3.5.0-27-generic.efi.signed root=/dev/sda8 ro   quiet splash elevator=deadline $vt_handoff
}
menuentry 'Linux Mint 14 Cinnamon 64-bit, 3.5.0-27-generic.efi.signed (/dev/sdb6) -- recovery mode' --class linuxmint --class gnu-linux --class gnu --class os {
	recordfail
	insmod gzio
	insmod part_gpt
	insmod ext2
	set root='hd1,gpt6'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6  ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	else
	  search --no-floppy --fs-uuid --set=root ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	fi
	echo	'Loading Linux 3.5.0-27-generic.efi.signed ...'
	linux	/vmlinuz-3.5.0-27-generic.efi.signed root=/dev/sda8 ro recovery nomodeset 
}
submenu "Previous Linux versions" {
menuentry 'Linux Mint 14 Cinnamon 64-bit, 3.5.0-27-generic (/dev/sdb6)' --class linuxmint --class gnu-linux --class gnu --class os {
	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_gpt
	insmod ext2
	set root='hd1,gpt6'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6  ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	else
	  search --no-floppy --fs-uuid --set=root ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	fi
	linux	/vmlinuz-3.5.0-27-generic root=UUID=39777fa9-0bb7-4301-ac98-379f12fd1bfb ro   quiet splash elevator=deadline $vt_handoff
	initrd	/initrd.img-3.5.0-27-generic
}
menuentry 'Linux Mint 14 Cinnamon 64-bit, 3.5.0-27-generic (/dev/sdb6) -- recovery mode' --class linuxmint --class gnu-linux --class gnu --class os {
	recordfail
	insmod gzio
	insmod part_gpt
	insmod ext2
	set root='hd1,gpt6'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6  ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	else
	  search --no-floppy --fs-uuid --set=root ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	fi
	echo	'Loading Linux 3.5.0-27-generic ...'
	linux	/vmlinuz-3.5.0-27-generic root=UUID=39777fa9-0bb7-4301-ac98-379f12fd1bfb ro recovery nomodeset 
	echo	'Loading initial ramdisk ...'
	initrd	/initrd.img-3.5.0-27-generic
}
menuentry 'Linux Mint 14 Cinnamon 64-bit, 3.5.0-17-generic (/dev/sdb6)' --class linuxmint --class gnu-linux --class gnu --class os {
	recordfail
	gfxmode $linux_gfx_mode
	insmod gzio
	insmod part_gpt
	insmod ext2
	set root='hd1,gpt6'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6  ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	else
	  search --no-floppy --fs-uuid --set=root ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	fi
	linux	/vmlinuz-3.5.0-17-generic root=UUID=39777fa9-0bb7-4301-ac98-379f12fd1bfb ro   quiet splash elevator=deadline $vt_handoff
	initrd	/initrd.img-3.5.0-17-generic
}
menuentry 'Linux Mint 14 Cinnamon 64-bit, 3.5.0-17-generic (/dev/sdb6) -- recovery mode' --class linuxmint --class gnu-linux --class gnu --class os {
	recordfail
	insmod gzio
	insmod part_gpt
	insmod ext2
	set root='hd1,gpt6'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6  ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	else
	  search --no-floppy --fs-uuid --set=root ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	fi
	echo	'Loading Linux 3.5.0-17-generic ...'
	linux	/vmlinuz-3.5.0-17-generic root=UUID=39777fa9-0bb7-4301-ac98-379f12fd1bfb ro recovery nomodeset 
	echo	'Loading initial ramdisk ...'
	initrd	/initrd.img-3.5.0-17-generic
}
}
### END /etc/grub.d/10_linux ###

### BEGIN /etc/grub.d/10_lupin ###
### END /etc/grub.d/10_lupin ###

### BEGIN /etc/grub.d/20_linux_xen ###

### END /etc/grub.d/20_linux_xen ###

### BEGIN /etc/grub.d/20_memtest86+ ###
menuentry "Memory test (memtest86+)" {
	insmod part_gpt
	insmod ext2
	set root='hd1,gpt6'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6  ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	else
	  search --no-floppy --fs-uuid --set=root ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	fi
	linux16	/memtest86+.bin
}
menuentry "Memory test (memtest86+, serial console 115200)" {
	insmod part_gpt
	insmod ext2
	set root='hd1,gpt6'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd1,gpt6 --hint-efi=hd1,gpt6 --hint-baremetal=ahci1,gpt6  ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	else
	  search --no-floppy --fs-uuid --set=root ced816a2-0bd1-4c7a-b43a-92cc57cffa6e
	fi
	linux16	/memtest86+.bin console=ttyS0,115200n8
}
### END /etc/grub.d/20_memtest86+ ###

### BEGIN /etc/grub.d/30_os-prober ###
menuentry 'Windows 8 (loader) (on /dev/sda4)' --class windows --class os $menuentry_id_option 'osprober-chain-DA885EE2885EBD27' {
	insmod part_gpt
	insmod ntfs
	set root='hd0,gpt4'
	if [ x$feature_platform_search_hint = xy ]; then
	  search --no-floppy --fs-uuid --set=root --hint-bios=hd0,gpt4 --hint-efi=hd0,gpt4 --hint-baremetal=ahci0,gpt4  DA885EE2885EBD27
	else
	  search --no-floppy --fs-uuid --set=root DA885EE2885EBD27
	fi
	drivemap -s (hd0) ${root}
	chainloader +1
}
### END /etc/grub.d/30_os-prober ###

### BEGIN /etc/grub.d/30_uefi-firmware ###
### END /etc/grub.d/30_uefi-firmware ###

### BEGIN /etc/grub.d/40_custom ###
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.
### END /etc/grub.d/40_custom ###

### BEGIN /etc/grub.d/41_custom ###
if [ -f  ${config_directory}/custom.cfg ]; then
  source ${config_directory}/custom.cfg
elif [ -z "${config_directory}" -a -f  $prefix/custom.cfg ]; then
  source $prefix/custom.cfg;
fi
### END /etc/grub.d/41_custom ###
--------------------------------------------------------------------------------

=================== sdb6: Location of files loaded by Grub: ====================

           GiB - GB             File                                 Fragment(s)

 898.842303276 = 965.124574208  grub/grub.cfg                                  1
 898.893548012 = 965.179597824  initrd.img-3.5.0-17-generic                    3
 898.973711014 = 965.265672192  initrd.img-3.5.0-27-generic                    2
 898.871234894 = 965.155639296  vmlinuz-3.5.0-17-generic                       1
 898.913956642 = 965.201511424  vmlinuz-3.5.0-27-generic                       1
 898.919817924 = 965.207804928  vmlinuz-3.5.0-27-generic.efi.signed            1

======================== Unknown MBRs/Boot Sectors/etc: ========================

Unknown GPT Partiton Type
dee2bfd3af3ddf11ba40e3a556d89593
Unknown BootLoader on sda2

00000000  eb 58 90 4d 53 44 4f 53  35 2e 30 00 02 08 fe 1b  |.X.MSDOS5.0.....|
00000010  02 00 00 00 00 f8 00 00  3f 00 ff 00 00 48 1f 00  |........?....H..|
00000020  00 20 08 00 01 02 00 00  00 00 00 00 02 00 00 00  |. ..............|
00000030  01 00 06 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
00000040  80 00 29 b8 66 5c d0 4e  4f 20 4e 41 4d 45 20 20  |..).f\.NO NAME  |
00000050  20 20 46 41 54 33 32 20  20 20 33 c9 8e d1 bc f4  |  FAT32   3.....|
00000060  7b 8e c1 8e d9 bd 00 7c  88 56 40 88 4e 02 8a 56  |{......|.V@.N..V|
00000070  40 b4 41 bb aa 55 cd 13  72 10 81 fb 55 aa 75 0a  |@.A..U..r...U.u.|
00000080  f6 c1 01 74 05 fe 46 02  eb 2d 8a 56 40 b4 08 cd  |...t..F..-.V@...|
00000090  13 73 05 b9 ff ff 8a f1  66 0f b6 c6 40 66 0f b6  |.s......f...@f..|
000000a0  d1 80 e2 3f f7 e2 86 cd  c0 ed 06 41 66 0f b7 c9  |...?.......Af...|
000000b0  66 f7 e1 66 89 46 f8 83  7e 16 00 75 39 83 7e 2a  |f..f.F..~..u9.~*|
000000c0  00 77 33 66 8b 46 1c 66  83 c0 0c bb 00 80 b9 01  |.w3f.F.f........|
000000d0  00 e8 2c 00 e9 a8 03 a1  f8 7d 80 c4 7c 8b f0 ac  |..,......}..|...|
000000e0  84 c0 74 17 3c ff 74 09  b4 0e bb 07 00 cd 10 eb  |..t.<.t.........|
000000f0  ee a1 fa 7d eb e4 a1 7d  80 eb df 98 cd 16 cd 19  |...}...}........|
00000100  66 60 80 7e 02 00 0f 84  20 00 66 6a 00 66 50 06  |f`.~.... .fj.fP.|
00000110  53 66 68 10 00 01 00 b4  42 8a 56 40 8b f4 cd 13  |Sfh.....B.V@....|
00000120  66 58 66 58 66 58 66 58  eb 33 66 3b 46 f8 72 03  |fXfXfXfX.3f;F.r.|
00000130  f9 eb 2a 66 33 d2 66 0f  b7 4e 18 66 f7 f1 fe c2  |..*f3.f..N.f....|
00000140  8a ca 66 8b d0 66 c1 ea  10 f7 76 1a 86 d6 8a 56  |..f..f....v....V|
00000150  40 8a e8 c0 e4 06 0a cc  b8 01 02 cd 13 66 61 0f  |@............fa.|
00000160  82 74 ff 81 c3 00 02 66  40 49 75 94 c3 42 4f 4f  |.t.....f@Iu..BOO|
00000170  54 4d 47 52 20 20 20 20  00 00 00 00 00 00 00 00  |TMGR    ........|
00000180  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
*
000001a0  00 00 00 00 00 00 00 00  00 00 00 00 0d 0a 44 69  |..............Di|
000001b0  73 6b 20 65 72 72 6f 72  ff 0d 0a 50 72 65 73 73  |sk error...Press|
000001c0  20 61 6e 79 20 6b 65 79  20 74 6f 20 72 65 73 74  | any key to rest|
000001d0  61 72 74 0d 0a 00 00 00  00 00 00 00 00 00 00 00  |art.............|
000001e0  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00  |................|
000001f0  00 00 00 00 00 00 00 00  ac 01 b9 01 00 00 55 aa  |..............U.|
00000200


=============================== StdErr Messages: ===============================

  No volume groups found

So my partitions are:

/dev/sda1 Windows diagnostic partition or something
/dev/sda2 EFI system partition
/dev/sda3 'Microsoft reserved partition', whatever that means
/dev/sda4 My main Windows partition (C drive)
/dev/sda5 Yet another hidden Windows partition
/dev/sda6 reserved by me for a possible future /boot
/dev/sda7 reserved by me for a possible future biosgrub
/dev/sda8 Mint 14 root
/dev/sdb1 /var
/dev/sdb2 /tmp
/dev/sdb3 SWAP
/dev/sdb4 /home/mikz
/dev/sdb5 an additional NTFS partition
/dev/sdb6 /boot
/dev/sdb7 biosgrub
/dev/sdb8 /home

And FWIW, this is a Lenovo T430s, with a SSD as /dev/sda, and a 1TB spinning disc as /dev/sdb

Again, any advice would be greatly appreciated. Cheers.

[anamnesis]

G'day people,

I've tried reinstalling grub from a live CD:

Hello
"a live CD". Which one? Grub 1.99 can't handle efi. Grab a live CD with grub 2.0 (!) and try again.Don't forget to chroot and don't forget to run sudo update-grub after the installation
Good luck!
Regards

[MikZ]

"a live CD". Which one? Grub 1.99 can't handle efi.

Just my Mint boot installation DVD, actually. It's grub 2.0:

Code: Select all

mint / # grub-install --version
grub-probe: error: cannot find a device for /boot (is /dev mounted?).
grub-install.real (GRUB) 2.00-7ubuntu11

And yes, /dev was mounted, and I was in a chroot shell at the time. But let me back up for a minute, and show the results of my latest attempts. In a new Mint 14 session off the DVD, and a new command window:

Code: Select all

sudo swapoff -av
mint@mint ~ $ alias ll='ls -althr'
mint@mint ~ $ ll /mnt
total 0
drwxr-xr-x 2 root root   3 Oct  9  2012 .
drwxr-xr-x 1 root root 240 May 11  2013 ..
mint@mint ~ $ sudo mount -t ext4 /dev/sda8 /mnt
mint@mint ~ $ sudo mount -t ext4 /dev/sdb1 /mnt/var
mint@mint ~ $ sudo mount -t ext4 /dev/sdb2 /mnt/tmp
mint@mint ~ $ sudo mount -t ext4 /dev/sdb6 /mnt/boot
mint@mint ~ $ sudo mount -t ext3 /dev/sdb8 /mnt/home
mint@mint ~ $ ll /mnt
total 133K
drwxr-xr-x   6 root root 4.0K Mar 23  2012 opt
drwxr-xr-x   2 root root 4.0K Jun 11  2012 selinux
drwxr-xr-x   2 root root 4.0K Jul 21  2012 sys
drwxr-xr-x   2 root root 4.0K Oct  9  2012 proc
drwxr-xr-x   2 root root 4.0K Oct  9  2012 mnt
drwxr-xr-x   2 root root 4.0K Oct 17  2012 srv
drwxr-xr-x   4 root root 4.0K Oct 17  2012 dev
drwxr-xr-x  10 root root 4.0K Nov  5  2012 run
drwx------   2 root root  16K Apr 17 00:47 lost+found
drwxr-xr-x   4 root root 4.0K Apr 17 00:47 reserve
drwxr-xr-x   3 root root 4.0K Apr 17 01:52 win
drwxr-xr-x   6 root root 4.0K Apr 17 03:34 home
drwxr-xr-x   4 root root 4.0K Apr 17 07:56 media
drwx------   9 root root 4.0K Apr 20 05:22 root
lrwxrwxrwx   1 root root   33 Apr 21 05:16 initrd.img.old -> /boot/initrd.img-3.5.0-27-generic
lrwxrwxrwx   1 root root   29 Apr 21 05:16 vmlinuz.old -> boot/vmlinuz-3.5.0-27-generic
lrwxrwxrwx   1 root root   32 Apr 21 05:17 initrd.img -> boot/initrd.img-3.5.0-27-generic
lrwxrwxrwx   1 root root   29 Apr 21 05:17 vmlinuz -> boot/vmlinuz-3.5.0-27-generic
drwxr-xr-x   4 root root 1.0K Apr 21 05:17 boot
drwxr-xr-x   2 root root  12K Apr 21 08:37 bin
drwxr-xr-x  12 root root 4.0K Apr 21 09:06 usr
drwxr-xr-x   2 root root 4.0K Apr 30 22:13 lib32
drwxr-xr-x   2 root root 4.0K Apr 30 22:13 lib64
drwxr-xr-x   2 root root  12K Apr 30 22:14 sbin
drwxr-xr-x  23 root root 4.0K Apr 30 22:14 lib
drwxr-xr-x  14 root root 4.0K May  1 02:53 var
drwxr-xr-x  26 root root 4.0K May  4 02:51 .
drwxr-xr-x 152 root root  12K May  4 04:46 etc
drwxrwxrwt  28 root root 4.0K May  4 08:01 tmp
drwxr-xr-x   1 root root  240 May 11  2013 ..
mint / # ls /boot
abi-3.5.0-17-generic     grub                         memtest86+.bin               vmlinuz-3.5.0-17-generic
abi-3.5.0-27-generic     initrd.img-3.5.0-17-generic  memtest86+_multiboot.bin     vmlinuz-3.5.0-27-generic
config-3.5.0-17-generic  initrd.img-3.5.0-27-generic  System.map-3.5.0-17-generic  vmlinuz-3.5.0-27-generic.efi.signed
config-3.5.0-27-generic  lost+found                   System.map-3.5.0-27-generic

So /mnt looks like / did on my system, and /mnt/boot looks like /boot, and is consistent with what I find when I drop to a command line from the grub menu (see above). But then there's this new error: 'grub-probe: error: failed to get canonical path of /cow'

Code: Select all

mint@mint ~ $ sudo grub-install --root-directory=/mnt/ /dev/sdb
grub-probe: error: failed to get canonical path of /cow.
Installation finished. No error reported.

Since it says it finished without error anyhow (despite the error), I tried running update-grub and rebooting. Same error:

Code: Select all

mint@mint ~ $ sudo update-grub
/usr/sbin/grub-probe: error: failed to get canonical path of /cow.

I tried a few other things:

Code: Select all

mint@mint ~ $ sudo grub-install --root-directory=/mnt/ --boot-directory=/mnt/boot/ /dev/sdb
grub-probe: error: failed to get canonical path of /cow.
Installation finished. No error reported.
mint@mint ~ $ df
Filesystem     1K-blocks    Used Available Use% Mounted on
/cow             3935896  221768   3714128   6% /
udev             3922332       4   3922328   1% /dev
tmpfs            1574360    1116   1573244   1% /run
/dev/sr0          901716  901716         0 100% /cdrom
/dev/loop0        858368  858368         0 100% /rofs
tmpfs            3935896      52   3935844   1% /tmp
none                5120       0      5120   0% /run/lock
none             3935896     608   3935288   1% /run/shm
none              102400      16    102384   1% /run/user
/dev/sda8      170745884 4587884 157484564   3% /mnt
/dev/sdb1        4128448 1750276   2168460  45% /mnt/var
/dev/sdb2       16513960  617976  15057124   4% /mnt/tmp
/dev/sdb6         190403   78041    102532  44% /mnt/boot
/dev/sdb8       33025904  213268  31135020   1% /mnt/home
mint@mint ~ $ sudo grub-install --recheck --root-directory=/mnt/ --boot-directory=/mnt/boot/ /dev/sdb
grub-probe: error: failed to get canonical path of /cow.

And yet, I still get the original 'Kernel Panic - not syncing: VFS : Unable to mount root fs on unknown-block(0,0)'

Don't forget to chroot and don't forget to run sudo update-grub after the installation

I tried that method, too. I guess I'm not mounting something correctly?

Code: Select all

mint@mint ~ $ sudo chroot /mnt
mint / # df
df: `/sys/fs/fuse/connections': No such file or directory
df: `/sys/kernel/debug': No such file or directory
df: `/sys/kernel/security': No such file or directory
df: `/run/user': No such file or directory
df: `/proc/sys/fs/binfmt_misc': No such file or directory
Filesystem     1K-blocks    Used Available Use% Mounted on
/dev/sda8      170745884 4587884 157484564   3% /
sysfs          170745884 4587884 157484564   3% /sys
udev           170745884 4587884 157484564   3% /dev
devpts         170745884 4587884 157484564   3% /dev/pts
/dev/sdb1        4128448 1750276   2168460  45% /var

I don't know what those first five paths are. Any idea what I'm doing wrong? Still, / and /boot look okay:

Code: Select all

mint / # ll /
total 137K
drwxr-xr-x   6 root root 4.0K Mar 23  2012 opt
drwxr-xr-x   2 root root 4.0K Jun 12  2012 selinux
drwxr-xr-x   2 root root 4.0K Jul 21  2012 sys
drwxr-xr-x   2 root root 4.0K Oct 10  2012 proc
drwxr-xr-x   2 root root 4.0K Oct 10  2012 mnt
drwxr-xr-x   2 root root 4.0K Oct 18  2012 srv
drwxr-xr-x   4 root root 4.0K Oct 18  2012 dev
drwxr-xr-x  10 root root 4.0K Nov  6  2012 run
drwx------   2 root root  16K Apr 17 10:47 lost+found
drwxr-xr-x   4 root root 4.0K Apr 17 10:47 reserve
drwxr-xr-x   3 root root 4.0K Apr 17 11:52 win
drwxr-xr-x   6 root root 4.0K Apr 17 13:34 home
drwxr-xr-x   4 root root 4.0K Apr 17 17:56 media
drwx------   9 root root 4.0K Apr 20 15:22 root
lrwxrwxrwx   1 root root   33 Apr 21 15:16 initrd.img.old -> /boot/initrd.img-3.5.0-27-generic
lrwxrwxrwx   1 root root   29 Apr 21 15:16 vmlinuz.old -> boot/vmlinuz-3.5.0-27-generic
lrwxrwxrwx   1 root root   32 Apr 21 15:17 initrd.img -> boot/initrd.img-3.5.0-27-generic
lrwxrwxrwx   1 root root   29 Apr 21 15:17 vmlinuz -> boot/vmlinuz-3.5.0-27-generic
drwxr-xr-x   4 root root 1.0K Apr 21 15:17 boot
drwxr-xr-x   2 root root  12K Apr 21 18:37 bin
drwxr-xr-x  12 root root 4.0K Apr 21 19:06 usr
drwxr-xr-x   2 root root 4.0K May  1 08:13 lib32
drwxr-xr-x   2 root root 4.0K May  1 08:13 lib64
drwxr-xr-x   2 root root  12K May  1 08:14 sbin
drwxr-xr-x  23 root root 4.0K May  1 08:14 lib
drwxr-xr-x  14 root root 4.0K May  1 12:53 var
drwxr-xr-x  26 root root 4.0K May  4 12:51 ..
drwxr-xr-x  26 root root 4.0K May  4 12:51 .
drwxr-xr-x 152 root root  12K May  4 14:46 etc
drwxrwxrwt  28 root root 4.0K May  4 18:01 tmp
mint / # ls /boot
abi-3.5.0-17-generic     grub                         memtest86+.bin               vmlinuz-3.5.0-17-generic
abi-3.5.0-27-generic     initrd.img-3.5.0-17-generic  memtest86+_multiboot.bin     vmlinuz-3.5.0-27-generic
config-3.5.0-17-generic  initrd.img-3.5.0-27-generic  System.map-3.5.0-17-generic  vmlinuz-3.5.0-27-generic.efi.signed
config-3.5.0-27-generic  lost+found                   System.map-3.5.0-27-generic

... but grub doesn't seem to think so:

Code: Select all

mint / # grub-install --recheck /dev/sdb
grub-probe: error: cannot find a device for /boot (is /dev mounted?).
Path `/boot/grub' is not readable by GRUB on boot. Installation is impossible. Aborting.

I didn't think I'd need to sudo in a sudoed chroot session, but just in case, I tried:

Code: Select all

mint / # sudo grub-install --recheck /dev/sdb
sudo: unable to resolve host mint
grub-probe: error: cannot find a device for /boot (is /dev mounted?).
Path `/boot/grub' is not readable by GRUB on boot. Installation is impossible. Aborting.

D'oh! More ideas, anyone?

Good luck!

Thanks, and thanks for taking a stab at it.

[anamnesis]

Hi,
you have a separate boot partion (sdb6). So, open shell in the live cd and:

sudo mkdir /mnt/boot
sudo mount /dev/sdb6 /mnt/boot

sudo mount /dev/sdb5 /mnt
sudo grub-install --root-directory=/mnt /dev/sdb

hth

[MikZ]

you have a separate boot partion (sdb6). So, open shell in the live cd and:

sudo mkdir /mnt/boot
sudo mount /dev/sdb6 /mnt/boot

sudo mount /dev/sdb5 /mnt
sudo grub-install --root-directory=/mnt /dev/sdb

Thanks, anamnesis. I'm aware of my partition setup, which is why I've used the --root-directory argument in every attempt, except when chroot was active—please see above.

Still, I tried mounting just /mnt/boot and /mnt as you suggested (except I pointed /mnt to the correct /dev/sda8 partition). The result was the old failed to get canonical path of /cow. I'm assuming that it's referring to the copy on write loop driver that my live CD uses, and that grub-probe wants to know where to copy its stuff from. But there's no cow subdirectory in /mnt or /dev, so I don't know where it is, nor how to give this information to grub-probe.

But I question whether grub-install alone is going to fix this problem. I wonder if an update got confused about my boot and root partitions being on separate drives, and something to messed up that I need to fix by hand—the fact that hd0 and hd1 mean different things in the config file and on the command line has made me suspicious. But I'm really just making vaguely educated guesses, and my education could include some more tutoring.

In the meantime, I'll play with the grub command line some more, and see if I can get a successful boot.

[MikZ]

Okay, I've gotten unstuck, with a lot of help from the Ubuntu's Grub2 troubleshooting page (especially the Search & Set section) and manually editing grub.cfg.

I created a new menuentry that looks like this:

Code: Select all

   recordfail
   gfxmode $linux_gfx_mode
   insmod gzio
   insmod part_gpt
   insmod ext2
   set prefix='(hd0,gpt6)/grub'
   set root='hd1,gpt8'
   linux   (hd0,6)/vmlinuz-3.5.0-27-generic.efi.signed root=/dev/sda8 ro   quiet splash elevator=deadline $vt_handoff
   initrd  (hd0,6)/initrd.img-3.5.0-27-generic

If you compare that with my post on 4 May, you'll see the first four lines are the same, but then I manually set the prefix variable, fix the root, specify the path to the kernel explicitly, and add initrd. I'm not sure whether all four of these changes are necessary, because I made all four edits at the grub menu, found they worked, and then updated grub.cfg.

The problem, of course, is that grub.cfg will be overwritten next time update-grub gets run. I think that perhaps the Mint installer created its own grub.cfg, and that update-grub got run in the meantime as part of an update. I think I can customise grub to add that menu option as part of update-grub—I've been reading this grub2 tutorial, and although it doesn't seem 100% accurate, it's given me a better idea about how it all works.

I'm pleased that I can boot my system, but the software engineer in me is uneasy about having fixed the problem without really understanding why, especially since this feels like a hack. A future update may even break it again. So if there's any well-thought advice out there, I'd really appreciate it. (By well-thought, I mean please check that I haven't already tried it. I know I've posted a lot of detail—this forum encourages it!—but your browser's find function can make this easy to spot.)

My guess is that grub-install wasn't able to translate my --root-directory parameter to 'hd1,gpt8', probably because it failed to get canonical path of /cow. Perhaps it came up with the messed up compromise of hd1,gpt6—right partition, wrong drive!—because hd0 and hd1 get swapped around when I boot off the CD? Does that make sense? Does anybody know how to correct this?