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Itserpol
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PostPosted: Fri Feb 05, 2010 6:47 am    Post subject: Boot partition won't mount, superblock error Reply with quote

Hi all. This is my second time installing Gentoo, and I'm not sure what's happening here.

When I boot Gentoo, it displays the following error about my boot partition (sdb1)

Code:
fsck.ext2: No such file or directory while trying to open /dev/sdb1
/dev/sdb1:
The superblock could not be read or does not describe a correct ext2 filesystem. If the device is valid and it really contains an ext2 filesystem (and not swap or ufs pr something else), then the superblock is corrupt, and you might try running e2fsck with an alternate superblock:
   e2fsck -b 8193 <device>


So of course when Gentoo attempts to mount sdb1, I get

Code:
mount: special device /dev/sdb1 does not exist


My searches have shown that other people with similar problems are rendered completely unable to boot, but for me Gentoo is able to finish booting from which point I can login as root and manually mount sdb1 to /boot. What's going on?

My fstab

Code:

/dev/sdb1     /boot         ext2     defaults,noatime         1 2
/dev/sdb2     none          swap     sw                       0 0
/dev/sdb3     /home         ext3     noatime                  0 2
/dev/sdb4     /             ext3     noatime                  0 1

/dev/sda2     /mnt/Win7     ntfs

/dev/cdrw     /mnt/cdrw     auto     noauto,user              0 0
/dev/dvd1     /mnt/dvd1     auto     noauto,user              0 0
/dev/fd0      /mnt/floppy   auto     noauto,user              0 0
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Jaglover
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PostPosted: Fri Feb 05, 2010 7:44 am    Post subject: Reply with quote

/boot does not need to be mounted, bootloader reads it at an early boot stage and boots the kernel from there. Once the kernel is loaded into RAM there is no need to access /boot.
Situation you describe is possible when ext2 support is built as module, thus not available before / is mounted.
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patrikas
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PostPosted: Fri Feb 05, 2010 9:30 am    Post subject: Reply with quote

Isn't the root file system the one which gets mounted first since it is pointed by bootloader ?

Firstly check ext2 support in .config. Last time I installed gentoo I had similar problem because ext2 was not selected by default and I didn't notice that.
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Jaglover
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PostPosted: Fri Feb 05, 2010 9:38 am    Post subject: Reply with quote

Itserpol,

your error will go away if you set noauto option for /boot as per handbook.

@patrikas
Quote:
Isn't the root file system the one which gets mounted first since it is pointed by bootloader ?
Yes, root filesystem is mounted as /.
Quote:
Firstly check ext2 support in .config. Last time I installed gentoo I had similar problem because ext2 was not selected by default and I didn't notice that.
OP states he can mount it after the system is booted.
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Itserpol
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PostPosted: Fri Feb 05, 2010 2:46 pm    Post subject: Reply with quote

Thanks for the quick replies!

As for ext2 support, I double checked and it is indeed built into the kernel (not as a module).
Is there any way I can fix this so that I don't have manually mount /boot? That could get a little annoying... :?
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Jaglover
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PostPosted: Sat Feb 06, 2010 10:47 am    Post subject: Reply with quote

Why you need to mount /boot all the time? It does not need to be mounted for Gentoo to function.
Anyhow, look into dmsg.
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Itserpol
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PostPosted: Sat Feb 06, 2010 5:03 pm    Post subject: Reply with quote

Well okay, I guess you're right. I really don't need to have /boot mounted all the time. But the same superblock error keeps coming up every time I start Gentoo. If I were to recreate the partition (after backing up my kernel and grub data of course), could that solve it?
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Mike Hunt
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PostPosted: Sat Feb 06, 2010 5:06 pm    Post subject: Reply with quote

But do mount boot before copying a new kernel to it. :)

Please post the output of
Code:
fdisk -l
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Itserpol
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PostPosted: Sun Feb 07, 2010 4:46 pm    Post subject: Reply with quote

Mike Hunt wrote:
But do mount boot before copying a new kernel to it. :)


Haha, yeah of course

Mike Hunt wrote:
Please post the output of
Code:
fdisk -l


Code:
Disk /dev/sda: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0x23668288

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          13      102400    7  HPFS/NTFS
Partition 1 does not end on cylinder boundary.
/dev/sda2              13       60802   488282112    7  HPFS/NTFS

Disk /dev/sdb: 500.1 GB, 500107862016 bytes
255 heads, 63 sectors/track, 60801 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xededd70e

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *           1           5       40131   83  Linux
/dev/sdb2               6          71      530145   82  Linux swap / Solaris
/dev/sdb3              72        6599    52436160   83  Linux
/dev/sdb4            6600       13127    52436160   83  Linux


sda is my Windows 7 drive, sdb is Gentoo
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Mike Hunt
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PostPosted: Sun Feb 07, 2010 5:12 pm    Post subject: Reply with quote

Ok, now we need to see your /boot/grub/grub.conf please.
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Itserpol
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PostPosted: Sun Feb 07, 2010 8:48 pm    Post subject: Reply with quote

Code:
default 0
timeout 10
splashimage=(hd1,0)/boot/grub/splash.xpm.gz

title Gentoo Linux 2.6.31-r6
root (hd1,0)
kernel /boot/kernel-2.6.31-gentoo-r6 root=/dev/sdb4 video=uvesafb:mtrr:3,ywrap,1600x1050@70

title Windows 7
rootnoverify (hd0,0)
makeactive
chainloader +1
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Itserpol
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PostPosted: Thu Feb 11, 2010 2:34 pm    Post subject: Reply with quote

I finally got around to recreating the boot partition and it didn't help, making me think it may be a hardware problem (I have had problems with this disk before).

Also, is it normal to have a symbolic link from /boot to /boot? I thought I could do without it when copying my backup data back onto the partition, but apparently grub can't find the kernel without it.
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John R. Graham
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PostPosted: Thu Feb 11, 2010 2:42 pm    Post subject: Reply with quote

Yes, it's normal. It's a convention so that your grub.conf kernel line looks the same whether /boot is on an independent mounted filesystem or just a directory off of your root filesystem. You could get rid of the symbolic link and then just specify your kernel line like
Code:
kernel /kernel-2.6.31-gentoo-r6 root=/dev/sdb4 video=uvesafb:mtrr:3,ywrap,1600x1050@70
but I don't recommend it.

Could you share the commands you used to recreate the filesystem?

- John

JRG: Edited for typos.
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Last edited by John R. Graham on Fri Feb 12, 2010 4:25 pm; edited 1 time in total
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Itserpol
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PostPosted: Thu Feb 11, 2010 8:15 pm    Post subject: Reply with quote

First I booted to my Gentoo liveUSB and started fdisk.
Code:

# fdisk /dev/sdb

Then I deleted the first partition (/boot), created a new partition 1 on the same space, made it bootable, and wrote my changes to the partition table. In lieu of a code box, my commands here were d, 1, n, p, enter, enter (using default cylinders), a, 1, w.

Next, I applied an ext2 filesystem.
Code:

# mke2fs /dev/sdb1

Finally, I created /mnt/gentoo/boot and /mnt/gentoo/home directories, mounted /dev/sdb1 and /dev/sdb3 to them (respectively), copied the backup onto /mnt/gentoo/boot, unmounted the partitions and rebooted.
Code:

# mkdir /mnt/gentoo/boot /mnt/gentoo/home
# mount /dev/sdb1 /mnt/gentoo/boot
# mount /dev/sdb3 /mnt/gentoo/home
# cp -R /mnt/gentoo/home/boot_backup/boot /mnt/gentoo
# umount /mnt/gentoo/boot /mnt/gentoo/home
# reboot
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Mike Hunt
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PostPosted: Thu Feb 11, 2010 10:54 pm    Post subject: Reply with quote

... and? Was rebooting successful?
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Itserpol
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PostPosted: Fri Feb 12, 2010 4:13 pm    Post subject: Reply with quote

Well, yeah. The rebooting went just fine. But the repartitioning didn't fix anything. I'm exactly where I was when I started.
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John R. Graham
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PostPosted: Fri Feb 12, 2010 4:31 pm    Post subject: Reply with quote

Could you post the output of
Code:
equery list -i e2fsprogs
or, alternatively,
Code:
eix e2fsprogs
please?

- John
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Itserpol
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PostPosted: Sat Feb 13, 2010 4:49 am    Post subject: Reply with quote

Code:

# equery list -i e2fsprogs
[ Searching for package 'e2fsprogs' in all categories among: ]
 * installed packages
[I--] [  ] sys-fs/e2fsprogs-1.41.9 (0)
[I--] [  ] sys-libs/e2fsprogs-libs-1.41.9 (0)
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BrummieJim
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PostPosted: Tue Feb 16, 2010 7:43 pm    Post subject: Reply with quote

Sorry if I'm hijacking this thread, but I have exactly the same problem, but it's on my root partition. My system was working fine before I updated the system with an emerge world on saturday. The system still boots fine, just boot and home aren't mounted. Home still has data on it, as I can mount it from a knoppix boot.

I have a knoppix USB device so I was going to run e2fsck on the partition without mounting it, is this a bad idea?

Is this a hardward fault and a sign of an aging drive? Had the computer for about two years.
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Jaglover
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PostPosted: Wed Feb 17, 2010 1:19 am    Post subject: Reply with quote

Did you forget running dispatch-conf.
Can you still mount those partitions from your Gentoo by hand. If not, what's the error message.
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BrummieJim
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PostPosted: Wed Feb 17, 2010 7:25 pm    Post subject: Reply with quote

In my case you can't mount any of the partitions as the /dev/sda doesn't exist.

I've run dispatch-conf and am running a revdep-rebuild now.

Any more suggestions?
Jim
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BrummieJim
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PostPosted: Thu Feb 18, 2010 1:09 am    Post subject: Reply with quote

trying ae2fsck -b 32768 /dev/sda7, but it comes up with lots of errors, I hit y to fix, but still gentoo can't detect the patitions.

Knoppix has no problem.
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hendric
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PostPosted: Sun Mar 02, 2014 9:18 am    Post subject: Sorry to necro old thread... Reply with quote

I was running into the same problem (boot partition does not mount by default, error listed in dmesg is "couldn't mount as ext2 due to feature incompatibility", but mount /dev/sda2 /boot worked fine) during my first install. I want /boot mounted as I will be experimenting with the kernel and need to change it frequently.

I did some testing, and here is what I found out.

Changing the filesystem type from ext2 to auto for grub2 seems to make it work, however dmesg still reports some complaints from EXT4-fs

(sda2): couldn't mount as ext3 due to feature incompatibilities
(sda2): couldn't mount as ext2 due to feature incompatibilities
(sda2): mounted filesystem with ordered data mode. Opts: (null)

mount reports
/dev/sda2 on /boot type ext4 (rw, noatime)

So I tried ext4 in /etc/fstab, and now /boot mounts fine.

My suspicion ss the installation for grub2 is overwriting the ext2 configuration done in the earlier step. Sound likely?


FWIW, I am installing into a VirtualBox VM, using a 64 bit OS.
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Hu
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PostPosted: Sun Mar 02, 2014 4:22 pm    Post subject: Reply with quote

hendric wrote:
My suspicion ss the installation for grub2 is overwriting the ext2 configuration done in the earlier step. Sound likely?
No. Also, you resurrected a thread last active in 2010. Although the original problem was never reported solved, it looks quite different from yours. Your problem is that you made boot an ext4 filesystem, then told the kernel to mount it as ext2. When you use the long form of mount, it defaults to -t auto.
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