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Linux udev tip: Assign Static SCSI Device Name

So how do you assign static names for SCSI device using udev under Linux? Simply use the scsi_id and other udev tools such as :

[a] scsi_id - retrieve and generate a unique SCSI identifier.
[b] udev_start - script to initialize /dev by using udev
[c] udevtest - simulate a udev run and print the action to the console.

What the hell is udev?

udev is the device manager for the Linux 2.6 kernel series. Its primary function is managing device nodes in /dev. Old UNIX system creates device in the /dev with static files. udev dynamically provides only the nodes for the devices actually present on a system.

Note following configuration is only tested on Gentoo / RHEL 5.x / CentOS 5.x Linux server systems but it should work with other distros with udev support.

Step # 1: Get WWID of the SCSI device

To get the WWID of /dev/sdd, type:
# scsi_id -g -u -s /block/sdd
Where,

  • -g : Treat the device as white listed
  • -u : Reformat the output
  • -s /bock/sdd : Generate an id for the /block/sdd (/dev/sdd). The mount point must not be included. For example, use /block/sdd, not /sys/block/sdd.

Step # 2: Create /etc/udev/rules.d/25-names.rules file

Open /etc/udev/rules.d/25-names.rules and append following text (replace WWID with actual id obtained from above command):

KERNEL=="sd*", BUS=="scsi", PROGRAM=="/sbin/scsi_id -g -u -s %p", RESULT=="WWID", SYMLINK+="scsiharddisk%n"

Above rule will create /dev/scsiharddisk (a symlink - select any other meaningful name as per your proecjet ) for the SCSI device with a given WWID. Please note that partitions on this device will be assigned the device names like /dev/scsiharddisk1, /dev/scsiharddisk2 and so on. Next, verify that everything is correct order, enter:
# udevtest
Start initialize /dev for new devices:
# start_udev
Verify symbolic links are created, enter:
# ls -l /dev/scsiharddisk*

Read the man pages for more information:
man scsi_id
man udevtest
man 7 udev

Mac ZFS Source Code Released

ZFS has amazing feature set and now it is ported to Mac

ZFS file system developed by Sun for its UNIX operating system. ZFS presents a pooled storage model that completely eliminates the concept of volumes and the associated problems of partitions, provisioning, wasted bandwidth and stranded storage. Thousands of filesystems can draw from a common storage pool, each one consuming only as much space as it actually needs. The combined I/O bandwidth of all devices in the pool is available to all filesystems at all times.

Apple has ported ZFS from Open Solaris to the Mac OS X platform. You can download ZFS beta version here (via ./).

If you are using hot swappable hard disk and created new partition using fdisk then you need to reboot Linux based system to get partition recognized. Without reboot you will NOT able to create filesystem on your newly created or modified partitions with the mke2fs command.

However with partprobe command you should able to create a new file system without rebooting the box. It is a program that informs the operating system kernel of partition table changes, by requesting that the operating system re-read the partition table.
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Asked by Payal K.

Q. I would like to know - can I access Linux ext3 partitions from windows 2000 server (dual boot) or windows XP desktop, as I have tons of MP3 and video files downloaded under Linux.

A. It is true that you can easily access your Windows partitions from Linux. However with small free utility called Explore2fs you can easily access Linux ext3 or ext2 partitions too without any problem.

Does ext3 work with windows?

Short answer - Yes.

You can always get your favorite MP3/video or PDF file stored inside Linux ext3 file system. This utility works on

  • Windows 95
  • Windows 98
  • Windows ME
  • Windows NT 4.0
  • Windows 2000
  • Windows XP
  • Windows Server 2003

However please note that I don't recommend to install this utility on a production Linux serer (if you have one) as it does not enforce security permission from windows operating system.One more thing before using this utility make sure you have a backup of all important data.

Download Explore2fs

=> You can download Explore2fs, the WIN32 explorer for Linux ext2fs partitions here.

Read and Write access to Linux file system from Windows

As pointed out by Anonymous user you can use Ext2 Installable File System For Windows, which provide Complete reading and writing access to files and directories of volumes with the Ext2 or Ext3 file system. You can download the software here.