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Recipe 9.12. Finding Device Names for mount and fstab
Use dmesg and fdisk. dmesg finds device names, and fdisk shows the partition numbers on hard drives. Referring to http://www.lanana.org/docs/device-list/devices.txt can be helpful as well, as it is the list of official /dev names. (If you have kernel sources installed, the devices.txt file may be present on your system in the /usr/src/* directory.)
This command searches dmesg for CD drives:
$ dmesg | grep -i cd hdc: ATAPI CDROM, ATAPI CD/DVD-ROM DRIVE hdc: ATAPI 40X CD-ROM DRIVE, 128K cache, UDMA (33)
A quick search in devices.txt reveals
Second IDE hard disk/CD-ROM interface 0 = /dev/hdc Master: whole disk (or CD-ROM)
Ignore the 0 = part; your device name is /dev/hdc.
This is what CD drives using the IDE-SCSI subsystem look like:
$ dmesg | grep -i cd hdb: TOSHIBA DVD-ROM SD-M1202, ATAPI CD/DVD-ROM drive hdc: LITE-ON LTR-24102B, ATAPI CD/DVD-ROM drive ide-cd: ignoring drive hdb ide-cd: ignoring drive hdc Type: CD-ROM ANSI SCSI revision: 02 Type: CD-ROM ANSI SCSI revision: 02 Attached scsi CD-ROM sr0 at scsi0, channel 0, id 0, lun 0 Attached scsi CD-ROM sr1 at scsi0, channel 0, id 1, lun 0 scd0: scsi3-mmc drive: 32x/32x cd/rw xa/form2 cdda tray Uniform CD-ROM driver Revision: 3.12 scd1: scsi3-mmc drive: 131x/40x writer cd/rw xa/form2 cdda tray
So the drive names are /dev/scd0 and /dev/scd1.
With hard drives, you must select specific partitions, since each partition is a separate block device. fdisk -l displays all partitions on all detected hard drives:
# /sbin/fdisk -l Disk /dev/hda: 20.5 GB, 20576747520 bytes 255 heads, 63 sectors/track, 2501 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/hda1 * 1 893 7172991 7 HPFS/NTFS /dev/hda2 894 1033 1124550 c W95 FAT32 (LBA) /dev/hda4 1034 2501 11791710 f W95 Ext'd (LBA) /dev/hda5 2437 2501 522081 82 Linux swap /dev/hda6 1034 1670 5116639+ 83 Linux /dev/hda7 1671 2436 6152863+ 83 Linux Partition table entries are not in disk order
Copy the device name from the Device column exactly as it is shown.
This is what a USB pen drive looks like in dmesg:
hub.c: new USB device 00:1d.0-2.3, assigned address 5 usb.c: USB device 5 (vend/prod 0x1915/0x2220) is not claimed ... SCSI device sda: 128000 512-byte hdwr sectors (66 MB) sda: Write Protect is off sda: sda1
Your device name is /dev/sda1.
This how fdisk sees USB drives:
# fdisk -l Disk /dev/sda: 65 MB, 65536000 bytes 8 heads, 32 sectors/track, 500 cylinders Units = cylinders of 256 * 512 = 131072 bytes Device Boot Start End Blocks Id System /dev/sda1 * 1 499 63856 6 FAT16
All storage devices are block devices in /dev. /dev names them according to their physical connections. For example:
Storage devices on Linux follow this naming convention:
IDE and USB devices that use the SCSI emulation subsystem are sometimes named /dev/sr*, which is symlinked to /dev/sd*.
If you have kernel sources installed, look for the devices.txt file to see the definitions of all those /dev names.
9.12.4 See Also
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