# [~~SOLVED~~] boot failure: no disk devices in /dev

## bglxx

hi members,

one of my servers was going down (maybe a defective power suppy), but it's not possible to start this system again, because the following message appears on screen:

```

 * Populating /dev with existing devices through uevents            [ ok ]

 * Waiting for uevents to be processed..                            [ ok ]

 * Mounting devpts at /dev/pts...                                   [ ok ]

 * Checking root filesystem...

fsck.ext4: No such file or directory while trying to open /dev/md2

/dev/md2

The superblock could not be read

...

...

Give root password

```

When I'm login as root, there are no disk devices in /dev. Nov /dev/sd? and no /dev/md?.

When I'm booting from USB stick, there are all devices available.

Does anyone knows why are my devices not available?

Thanks in advance - BerndLast edited by bglxx on Thu Sep 16, 2010 5:02 pm; edited 3 times in total

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## mcanswer

Have you recently (after last reboot) upgraded your kernel, udev or initrd? What is an output of "dmesg | grep -e sd -e md"? If you manually create needed device nodes (mknod /dev/sda b 8 0 ) are they readable? [/quote]

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## bglxx

 *Quote:*   

> Have you recently (after last reboot) upgraded your kernel, udev or initrd?

 

no, there are no changes since last boot.

 *Quote:*   

> What is an output of "dmesg | grep -e sd -e md"? 

 

```

Command line: root=/dev/ram0 init=/linuxrc ramdisk=8192 real_root=/dev/md2 udev

Kernel command line: root=/dev/ram0 init=/linuxrc ramdisk=8192 real_root=/dev/md2 udev

ata1: SATA max UDMA/133 cmd 0xd480 ctl 0xd400 bmdma 0xcc00 irq 23

ata2: SATA max UDMA/133 cmd 0xd080 ctl 0xd000 bmdma 0xcc08 irq 23

ata3: SATA max UDMA/133 cmd 0xc880 ctl 0xc800 bmdma 0xc080 irq 22

ata4: SATA max UDMA/133 cmd 0xc480 ctl 0xc400 bmdma 0xc088 irq 22

ata5: SATA max UDMA/133 cmd 0xc000 ctl 0xbc00 bmdma 0xb480 irq 21

ata6: SATA max UDMA/133 cmd 0xb880 ctl 0xb800 bmdma 0xb488 irq 21

sd 0:0:0:0: [sda] 976773168 512-byte logical blocks: (500 GB/465 GiB)

sd 0:0:0:0: [sda] Write Protect is off

sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00

sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA

 sda: sda1 sda2 sda3 sda4

sd 0:0:0:0: [sda] Attached SCSI disk

sd 1:0:0:0: [sdb] 976773168 512-byte logical blocks: (500 GB/465 GiB)

sd 1:0:0:0: [sdb] Write Protect is off

sd 1:0:0:0: [sdb] Mode Sense: 00 3a 00 00

sd 1:0:0:0: [sdb] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA

sd 2:0:0:0: [sdc] 1953525168 512-byte logical blocks: (1.00 TB/931 GiB)

sd 2:0:0:0: [sdc] Write Protect is off

sd 2:0:0:0: [sdc] Mode Sense: 00 3a 00 00

sd 2:0:0:0: [sdc] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA

 sdc:

 sdb: sdc1

sd 2:0:0:0: [sdc] Attached SCSI disk

 sdb1 sdb2 sdb3 sdb4

sd 1:0:0:0: [sdb] Attached SCSI disk

md: raid1 personality registered for level 1

md: raid6 personality registered for level 6

md: raid5 personality registered for level 5

md: raid4 personality registered for level 4

sd 3:0:0:0: [sdd] 1953525168 512-byte logical blocks: (1.00 TB/931 GiB)

sd 3:0:0:0: [sdd] Write Protect is off

sd 3:0:0:0: [sdd] Mode Sense: 00 3a 00 00

sd 3:0:0:0: [sdd] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA

sd 4:0:0:0: [sde] 1953525168 512-byte logical blocks: (1.00 TB/931 GiB)

sd 4:0:0:0: [sde] Write Protect is off

sd 4:0:0:0: [sde] Mode Sense: 00 3a 00 00

sd 4:0:0:0: [sde] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA

 sde:

 sdd: sdd1

sd 3:0:0:0: [sdd] Attached SCSI disk

 sde1

sd 4:0:0:0: [sde] Attached SCSI disk

sd 0:0:0:0: Attached scsi generic sg0 type 0

sd 1:0:0:0: Attached scsi generic sg1 type 0

sd 2:0:0:0: Attached scsi generic sg2 type 0

sd 3:0:0:0: Attached scsi generic sg3 type 0

sd 4:0:0:0: Attached scsi generic sg4 type 0

md: raid0 personality registered for level 0

md: raid10 personality registered for level 10

md: Autodetecting RAID arrays.

md: Scanned 11 and added 11 devices.

md: autorun ...

md: considering sde1 ...

md:  adding sde1 ...

md:  adding sdd1 ...

md: sdb4 has different UUID to sde1

md: sdb3 has different UUID to sde1

md: sdb2 has different UUID to sde1

md: sdb1 has different UUID to sde1

md:  adding sdc1 ...

md: sda4 has different UUID to sde1

md: sda3 has different UUID to sde1

md: sda2 has different UUID to sde1

md: sda1 has different UUID to sde1

md: created md4

md: bind<sdc1>

md: bind<sdd1>

md: bind<sde1>

md: running: <sde1><sdd1><sdc1>

raid5: device sde1 operational as raid disk 2

raid5: device sdd1 operational as raid disk 1

raid5: device sdc1 operational as raid disk 0

raid5: allocated 3222kB for md4

raid5: raid level 5 set md4 active with 3 out of 3 devices, algorithm 2

 disk 0, o:1, dev:sdc1

 disk 1, o:1, dev:sdd1

 disk 2, o:1, dev:sde1

md4: detected capacity change from 0 to 2000404348928

md: considering sdb4 ...

md:  adding sdb4 ...

md: sdb3 has different UUID to sdb4

md: sdb2 has different UUID to sdb4

md: sdb1 has different UUID to sdb4

md:  adding sda4 ...

md: sda3 has different UUID to sdb4

md: sda2 has different UUID to sdb4

md: sda1 has different UUID to sdb4

md: created md3

md: bind<sda4>

md: bind<sdb4>

md: running: <sdb4><sda4>

raid1: raid set md3 active with 2 out of 2 mirrors

md3: detected capacity change from 0 to 414044061696

md: considering sdb3 ...

md:  adding sdb3 ...

md: sdb2 has different UUID to sdb3

md: sdb1 has different UUID to sdb3

md:  adding sda3 ...

md: sda2 has different UUID to sdb3

md: sda1 has different UUID to sdb3

md: created md2

md: bind<sda3>

md: bind<sdb3>

md: running: <sdb3><sda3>

raid1: raid set md2 active with 2 out of 2 mirrors

md2: detected capacity change from 0 to 68730355712

md: considering sdb2 ...

md:  adding sdb2 ...

md: sdb1 has different UUID to sdb2

md:  adding sda2 ...

md: sda1 has different UUID to sdb2

md: created md1

md: bind<sda2>

md: bind<sdb2>

md: running: <sdb2><sda2>

raid1: raid set md1 active with 2 out of 2 mirrors

md1: detected capacity change from 0 to 17190748160

md: considering sdb1 ...

md:  adding sdb1 ...

md:  adding sda1 ...

md: created md0

md: bind<sda1>

md: bind<sdb1>

md: running: <sdb1><sda1>

raid1: raid set md0 active with 2 out of 2 mirrors

md0: detected capacity change from 0 to 139722752

md: ... autorun DONE.

 md2: unknown partition table

EXT3-fs (md2): error: couldn't mount because of unsupported optional features (240)

EXT2-fs (md2): error: couldn't mount because of unsupported optional features (240)

EXT4-fs (md2): mounted filesystem with ordered data mode

 md0: unknown partition table

```

 *Quote:*   

> If you manually create needed device nodes (mknod /dev/sda b 8 0 ) are they readable?

 

mknod /dev/sda b 8 0 creates the device and its accessible

mknod /dev/md0 b 9 0 creates the raid device and its also accessible

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## mcanswer

Your dmesg looks just fine. It's from corrupted system or when you boot from usb?

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## bglxx

 *Quote:*   

> Your dmesg looks just fine. It's from corrupted system or when you boot from usb?

 

its from the corrupted system.

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## mcanswer

In my opinion, your problem is udev - related. Try to reemerge udev or rebuild your initrd. Why did you append udev option to kernel command line? I'm not sure, but shouldn't be dev=udev?

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## bglxx

 *Quote:*   

> In my opinion, your problem is udev - related. Try to reemerge udev or rebuild your initrd.

 

I've tried to boot with the previos kernel and initrd and the result is the same. Tomorrow I will reemerge the udev. Hope this helps.

 *Quote:*   

>  Why did you append udev option to kernel command line?

 

Thats an automatic generated command line from grub installer.

 *Quote:*   

>  I'm not sure, but shouldn't be dev=udev?

 

I will take a look at the docs.

Thank you for your ideas, I hope, I can tell you tomorrow that it works because this is the prototype of a new generation of inhouse servers. Old generation runs without any difficulties since years.

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## bglxx

10 points to Poland   :Very Happy: 

I've done following:

```

mknod /dev/md0 b 9 0

mknod /dev/md1 b 9 1

mknod /dev/md2 b 9 2

mknod /dev/md3 b 9 3

mount -no remount,rw /

emerge -a udev

shutdown -rf now

```

and the system starting is okay.

Thanks for helping me.   :Very Happy: 

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## bglxx

sorry, but its not solved:

the system boots and works fine, but there are no devices like /dev/sda or dev/md0 into the /dev directory.

"mount" tells me, that / is mounted to /dev/md2 and "cat /proc/mdstat" ist telling me, that there some /dev/md? devices containing /dev/sd? disks

now I'm confused

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## bglxx

I've compiled a new kernel 2.6.34-gentoo-r6 and now it works. Don't know why.

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