topic Re: USB disk error in Operating System - Linux

USB disk error

Adithyan — Thu, 16 Aug 2007 12:44:47 GMT

Hi,

I am plugging a 500GB USB external disk in to my server. The following error comes.

The device /dev/sdgg1 is being put in devlabel's temporary ignore list /etc/sysconfig/devlabel.d/ignore_list to avoid errors.

How would I overcome this.

Pls help

Adithyan

Re: USB disk error

Adithyan — Thu, 16 Aug 2007 13:07:21 GMT

Anything can be done with rmmod modeprobe...????

Re: USB disk error

Matti_Kurkela — Thu, 16 Aug 2007 14:50:12 GMT

This is not related to modprobe or the kernel modules at all. The message is generated by "devlabel", which is a helper daemon.

If my understanding is correct, the devlabel daemon tries to maintain "persistent names" for your disks. If you use more than one hot-pluggable disk, the persistent names would be very convenient - but they aren't absolutely necessary.

For example:
Today, you plug in your 500 GB disk and it becomes /dev/sdg1. You might also plug in your handy USB stick for moving some scripts around, which would then become /dev/sdh1.

Tomorrow, you might reboot the server and then plug in these two devices in the reverse order. Now your USB stick is /dev/sdg1 and your 500 GB disk is /dev/sdh1 !

It would be nice to have a way to refer to the 500 GB disk with some name that does not care whether the disk is currently /dev/sdg1, /dev/sdh1 or /dev/whatever. Devlabel tries to do that by providing symlinks in the /dev/ directory. With some configuration, it might be possible to have devlabel create a symlink named /dev/my_500gb_usb_disk which would always point to the disk, whatever the disk's real device name might be.

But in your system, devlabel is apparently refusing to do this.

You should be able to use the disk as /dev/sdg1 even though devlabel does not work with that particular disk. You'll just need to keep track of the device name by yourself.
(I assume "/dev/sdgg1" is a typo. If not, you have a lot of disks...)

By the way, devlabel was originally created for Linux 2.4 kernel series. Newer distributions use Linux 2.6 series of kernels, and they generally have a more flexible system to replace the functionality of devlabel. It's called "udev".

The fact that you use "devlabel" indicates you're using a fairly old Linux distribution. Are you fully up to date with patches?

MK

Re: USB disk error

Adithyan — Fri, 17 Aug 2007 00:08:47 GMT

Hi Mark,

Thanks for the clarification. Yes your assumption is correct. I have lot of external disks addigned to the server from stoage. /dev/sdgg1 is not typo.

Since I have only one hot pluggable device, the chance of getting the device name change is little I guess??. I could unmount the device without any problem, but when I tried to mount it back using the command "mount /dev/sdgg1 /mnt/hd1" it was throwing an error " not a block special device". What could be wrong?

Thanks

Re: USB disk error

Ivan Kuznetsov — Fri, 17 Aug 2007 02:21:13 GMT

Hello!

Is /dev/sdgg1 a real device name? You can see device type, major and minor numbers by typing ls -l /dev/sdgg.
E.g.

[root@me wiki]# ls -l /dev/sda1
brw-rw---- 1 root disk 8, 1 Feb 2 2005 /dev/sda1

Here "b" (at permission field "brw-rw----") means block device, "8" is a major number (means SCSI disk) and "1" is a minor number (first partition of /dev/sda)

Also you can get kernel log messages (using 'dmesg' command) and see what kernel thinks about your USB disk.
E.g.

Aug 17 11:08:24 me kernel: Product: USB Disk
Aug 17 11:08:24 me kernel: SerialNumber: 192B1AA102D7
Aug 17 11:08:29 me kernel: SCSI device sda: 253952 512-byte hdwr sectors (130 MB)
Aug 17 11:08:29 me kernel: sda: Write Protect is off
Aug 17 11:08:29 me kernel: sda:<7>usb-storage: queuecommand() called
Aug 17 11:08:29 me kernel: sda1

Regards, Ivan Kuznetsov