File system is read-only but shouldn't be

[marian42]

Hi,

I tried to install owncloud on my rpi and somehow it failed.
Now every command I use returns some error message that says my file system is read-only.

Owncloud isn't really my priority anymore (altough it woudl be nice to have), I just want everything else to work again...
For example, apache won't start because it can't get write access to /var/log/apache2/error.log

What can I do to make apache and everything else run again?

Thanks

[cpc464]

Put your SD card into another linux system and do an fsck on it.

[marian42]

Code: Select all

fsck from util-linux 2.25.1
e2fsck 1.42.10 (18-May-2014)
ext2fs_open2: Bad magic number in super-block
fsck.ext2: Superblock invalid, trying backup blocks...
fsck.ext2: Bad magic number in super-block while trying to open /dev/mmcblk0p1

The superblock could not be read or does not describe a valid ext2/ext3/ext4
filesystem.  If the device is valid and it really contains an ext2/ext3/ext4
filesystem (and not swap or ufs or something else), then the superblock
is corrupt, and you might try running e2fsck with an alternate superblock:
    e2fsck -b 8193 <device>
 or
    e2fsck -b 32768 <device>

Not sure if this was the correct device though.

[DirkS]

Not sure if this was the correct device though.

It wasn't. You checked the first partition on the sd card, and it's probably the FAT partition

Did you do as suggested and use an SD card reader in another Pi (or other Linux system)?
In that case the partition to check is most likely /dev/sda2

[marian42]

I used a laptop with ubuntu.

Code: Select all

lsblk
NAME        MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda           8:0    0 238.5G  0 disk 
├─sda1        8:1    0   300M  0 part 
├─sda2        8:2    0   100M  0 part /boot/efi
├─sda3        8:3    0   128M  0 part 
├─sda4        8:4    0 194.8G  0 part 
└─sda5        8:5    0  33.9G  0 part /
mmcblk0     179:0    0   7.4G  0 disk 
└─mmcblk0p1 179:1    0   3.7G  0 part 

The sd card has 8GB, so by the size it should be the last one.

[DougieLawson]

It looks like something has trashed the partition table on that device.

Do you have a backup?

[marian42]

I don't have one that is up to date.
Could the pi boot with a broken partition table? (It does boot)

[DougieLawson]

Any backup is OK, we only need to look at the partition table with sudo fdisk -l to get the start & end sectors, length and format for each partition.

We can then write a new partition table to the borked card and that should fix the damage.

[marian42]

I have an .img file from December 2013, this should do it.

[DougieLawson]

You can run fdisk -l against that *.img.

[marian42]

From the image:

Code: Select all

fdisk -l rpi.img

Disk rpi.img: 3.8 GiB, 4075290624 bytes, 7959552 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x000f06b6

Device     Boot   Start     End Sectors  Size Id Type
rpi.img1           2048 2466796 2464749  1.2G  e W95 FAT16 (LBA)
rpi.img2        2473984 7959551 5485568  2.6G 85 Linux extended
rpi.img5        2482176 2596863  114688   56M  c W95 FAT32 (LBA)
rpi.img6        2605056 7959551 5354496  2.6G 83 Linux

Without the image:

Code: Select all

sudo fdisk -l

Disk /dev/sda: 238.5 GiB, 256060514304 bytes, 500118192 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: gpt
Disk identifier: 8C1EF8C0-4264-4568-BDC1-752906F0CD69

Device         Start       End   Sectors   Size Type
/dev/sda1       2048    616447    614400   300M Windows recovery environment
/dev/sda2     616448    821247    204800   100M EFI System
/dev/sda3     821248   1083391    262144   128M Microsoft reserved
/dev/sda4    1083392 409602047 408518656 194.8G Microsoft basic data
/dev/sda5  409602048 480585727  70983680  33.9G Linux filesystem

Disk /dev/mmcblk0: 7.4 GiB, 7948206080 bytes, 15523840 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x000f06b6

Device         Boot   Start      End  Sectors  Size Id Type
/dev/mmcblk0p1         2048  2466796  2464749  1.2G  e W95 FAT16 (LBA)
/dev/mmcblk0p2      2473984 15523839 13049856  6.2G 85 Linux extended
/dev/mmcblk0p5      2482176  2596863   114688   56M  c W95 FAT32 (LBA)
/dev/mmcblk0p6      2605056 15523839 12918784  6.2G 83 Linux

Not sure if the partition table is actually broken.

[DougieLawson]

You're comparing apples vs oranges.

The image is a 4GB card the broken one is an 8GB card.

But generally the start sectors are identical. So that bit is OK.

[marian42]

Solution: The problem was caused by a wrong edit to the /etc/fstab file. I could gain write access by remounting /dev/sda and edited the fstab file. Now everything works fine, I could even get owncloud to work. Thank you for helping

[cpc464]

Good news.

You fixed it by mounting the Pi partition on another Linux system and fixing the /etc/fstab file.

What was the fix to the file, for people having this problem in future ?

Just a note about fsck: Not sure what fsck command you used, but fsck has to be run on the partition with the suspected problem. In your case this would have been

fsck /dev/mmcblk0p2
or
fsck /dev/mmcblk0p6

The "bad magic number" messages are often caused by using the wrong device. Sometimes people typing something like fsck /dev/mmcblk0 (a devfice referring to the whole device, not the partition).

Cheers,
Jim

[marian42]

You fixed it by mounting the Pi partition on another Linux system and fixing the /etc/fstab file.

I actually did it by remounting /dev/sda on the pi itself. I first thought that this wasn't possible because I was using the mount commant wrong.

What was the fix to the file, for people having this problem in future ?

The file was fine and I broke it by adding "permissions" to the root filesystem. It should go to an entry for an NTFS hard drive.

[ioha]

see marian42, you got it finally. congrats