# Missing devicefiles for partitions

## marjue_1

Hi

I have a new installed Gentoo server with software raid on it. I developed this system on a temporary hardware and everything was fine.

Now after the move on the final hardware i have the following problem.

The system boots up fine.

The raid is damaged:

```
Personalities : [linear] [raid0] [raid1] [raid6] [raid5] [raid4] [multipath]

md126 : active raid1 sda1[0]

      48064 blocks [2/1] [U_]

md4 : active raid1 sda4[0]

      145479040 blocks [2/1] [U_]

md127 : active raid1 sda3[0]

      9767424 blocks [2/1] [U_]
```

When i tried to readd the sdbx partitions i noticed that there is /dev/sdb but no /dev/sdb1 or sdb2 or ....

But there are partitions:

```
fdisk -l /dev/sdb

Disk /dev/sdb: 160.0 GB, 160041885696 bytes, 312581808 sectors

Units = Sektoren of 1 * 512 = 512 bytes

Sector size (logical/physical): 512 bytes / 512 bytes

I/O size (minimum/optimal): 512 bytes / 512 bytes

Disk identifier: 0x484d5754

   Gerät  boot.     Anfang        Ende     Blöcke   Id  System

/dev/sdb1   *          63       96389       48163+  fd  Linux raid autodetect

/dev/sdb2           96390     2088449      996030   82  Linux Swap / Solaris

/dev/sdb3         2088450    21623489     9767520   fd  Linux raid autodetect

/dev/sdb4        21623490   312581807   145479159   fd  Linux raid autodetect
```

What is wrong in my system?

Thanks for help.

Bye

Marcus

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## NeddySeagoon

marjue_1,

Welcome to Gentoo.

You have a partition table on /dev/sdb, that does not mean there is anything behind it.  Lets mount /dev/sdb1, in readonly mode as a test. 

```
mount -o ro,offset=32256 /dev/sdb /mnt/cdrom
```

Now look around /mnt/cdrom and see if it looks like /dev/sdb1

The offset= option tells mount to look for a filesystem =bytes from the start of the block device given.

32256 bytes is 63 sectors from the start of /dev/sdb, which is just where /dev/sdb1 should be, if its still there.

Readonly stops you changing the filesystem accidently.

Do you have any other /dev/sd* devices ?

Your dmesg output would be useful, can you put it onto a pastebin?

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## marjue_1

Hi

I have moutet /dev/sdb as you suggested. I can see the files from the /boot filesystem which is normally mouted from /dev/md126

```
ls -l /mnt/cdrom

insgesamt 18903

lrwxrwxrwx 1 root root       1 21. Jul 2012  boot -> .

drwxr-xr-x 2 root root    1024 20. Feb 16:15 grub

-rw-r--r-- 1 root root 2796575 21. Jul 2012  initramfs-genkernel-x86-3.3.8-gentoo

-rw-r--r-- 1 root root 1806856 29. Jan 20:26 initramfs-genkernel-x86-3.5.7-gentoo

-rw-r--r-- 1 root root 4720624 17. Jan 21:59 kernel

-rw-r--r-- 1 root root 4963632  2. Feb 16:58 kernel_3.5.7

-rw-r--r-- 1 root root 4971792 21. Jul 2012  kernel_old

drwx------ 2 root root   12288 20. Jul 2012  lost+found
```

These are the sdx files from /dev

```
ls -l /dev/sd*

brw-rw---- 1 root disk 8,  0 28. Feb 15:06 /dev/sda

brw-rw---- 1 root disk 8,  1 28. Feb 15:06 /dev/sda1

brw-rw---- 1 root disk 8,  2 28. Feb 15:06 /dev/sda2

brw-rw---- 1 root disk 8,  3 28. Feb 15:06 /dev/sda3

brw-rw---- 1 root disk 8,  4 28. Feb 15:06 /dev/sda4

brw-rw---- 1 root disk 8, 16  6. Mär 09:34 /dev/sdb
```

i will send dmsg in a few minutes

Bye

Marcus

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## marjue_1

Here the dmsg

there is a "[    3.414138]  sdb: unable to read partition table". But why! The drive is working. I have already re-written the table.

Is it possible to rescan the IDE-bus. I know a script from SuSE to rescan the SCSI-bus for new drives during uptime.

Because of the old hardware i was forced to plug the drives on a single parallel-IDE Port as master/slave (jumper is on drive-select).

In the developing machine the drives have been on two controllers as master. Is there something missing in the kernel?

The pastebin'ed dmsg

http://de.pastebin.ca/2329461

Bye

Marcus

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## NeddySeagoon

marjue_1,

Jumpering the drives to cable select only works when 

a) your motherboard supports cable select

b) you use 80 wire IDE cables

c) your drives support cable select.

d) the IDE cable is fitted the right way round - it has a motherboard end[1].

I suspect something does not support cable select.

The good news is that you can emulate it.

Set the jumpers on the drives as follows:-

Set the drive at the end of the IDE cable to master

Set the drive in the middle of the IDE cable to slave.  

Thats what cable select does, so setting the jumpers this way is harmless, even if you do have working cable select.

The IDE bus cannot be rescanned.  Unlike SCSI it does not support hot plugging devices, so there is no point.

You will hate raid on two drives on the same IDE cable as commands to the drives cannot be overlapped.

This makes it very slow.

dmesg shows that sdb appears to be present but that it cannot be read - see all the resets and errors for sdb.

This may be as a result of both drives attempting to respond to commands sent to sdb because your cable select doesn't work.

[1]to determine the IDE cable ends, look at the cable close to the two end connectors. Notice that at one end, one wire is cut short.

The end with one wire cut short goes to the master drive.

This wire is connected to 0v on the motherboard and is connected to the slave drive only, where the 0v sets the drive to slave mode.

As its not connected to the master, the voltage there remains high (5v), which selects master mode.

This only works with 80 wire IDE cables.

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## marjue_1

Hi NeddySeagoon

Yes i know all these limitations. I was forced to do so because i only had old hardware for the developing machine and the production machine is not really better   :Rolling Eyes: 

But i didn't know that cable select only works on 80-pin cables   :Shocked: 

I will set the jumpers to real master and slave and check the other things you told me

And then i will ask the boss of the company for SATA drives

Thanks for help .... i will report in some days

Bye

Marcus

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## _______0

cheap ass boss

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