USB drive not being recognized under Linux

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In order to access USB drive under Linux you need to load special USB driver and support must be included in running Linux kernel. Try following command one by one to solve your problem:

Step # 1 : Make sure your external drive detected by system
Run dmesg command which print or control the kernel ring buffer:

# dmesg


# dmesg | grep –i USB


usbcore: registered new driver usbfs
usbcore: registered new driver hub
USB Universal Host Controller Interface driver v2.3
uhci_hcd 0000:00:1d.0: new USB bus registered, assigned bus number 1
hub 1-0:1.0: USB hub found
uhci_hcd 0000:00:1d.1: new USB bus registered, assigned bus number 2
hub 2-0:1.0: USB hub found
uhci_hcd 0000:00:1d.2: new USB bus registered, assigned bus number 3
usb 1-2: new full speed USB device using uhci_hcd and address 2
hub 3-0:1.0: USB hub found

As you see USB support is included in kernel. You can also verify this with following command:

# lspci -v | grep HCI


0000:00:1d.0 USB Controller: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #1 (rev 02) (prog-if 00 [UHCI])
0000:00:1d.1 USB Controller: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #2 (rev 02) (prog-if 00 [UHCI])
0000:00:1d.2 USB Controller: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #3 (rev 02) (prog-if 00 [UHCI])
0000:00:1d.7 USB Controller: Intel Corporation 82801DB/DBM (ICH4/ICH4-M) USB2 EHCI Controller (rev 02) (prog-if 20 [EHCI])

Step # 2 : Load USB modules/driver
If you cannot see your external USB drive in above dmesg output then try to load usb-uhci and usb-ohci modules (driver):

# modprobe usb-uhci
# modprobe usb-ohci
# modprobe usb-storage

Now again run dmesg:

# dmesg


usb 4-1: new high speed USB device using ehci_hcd and address 3
scsi2 : SCSI emulation for USB Mass Storage devices
usb-storage: device found at 3
usb-storage: waiting for device to settle before scanning
Vendor: SAMSUNG   Model: SV4002H           Rev: 0811
Type:   Direct-Access                      ANSI SCSI revision: 00
SCSI device sdb: 78242976 512-byte hdwr sectors (40060 MB)
sdb: assuming drive cache: write through
SCSI device sdb: 78242976 512-byte hdwr sectors (40060 MB)
sdb: assuming drive cache: write through
 sdb: sdb1
sd 2:0:0:0: Attached scsi disk sdb
usb-storage: device scan complete

Step 3 : Use external USB drive
As you see device sdb assigned to an external USB drive use mount command to mount drive:
List partitions on /dev/sdb:

# fdisk -l | grep sdb


Disk /dev/sda doesn't contain a valid partition table
Disk /dev/sdb: 40.0 GB, 40060403712 bytes
/dev/sdb1               1        4870    39118243+   c  W95 FAT32 (LBA)

Now mount partition:

# mount /dev/sdb1 /mnt

See also:

How do I find the path to a command file?

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You can use command which (use to locate a command). which returns the pathnames of the files which would be executed in the current environment, had its arguments been given as commands in a strictly POSIX-conformant shell. It does this by searching the PATH for executable files matching the names of the arguments.

which {command-name}


$ which ls


$ which gcc


See also:

How do I remotely administer a Windows server running IIS 6.0 web server from a Windows XP Professional dekstop system?

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MS Internet Information Services (IIS) is a set of Internet-based services such as NTP, FTP, HTTP/HTTPS, SMPT, NNTP etc. It is the world’s second most used web server (number one is Apache Web server).

You need to use IIS 6.0 Manager for Windows XP. With IIS 6.0 Manager for Windows XP, administrators can remotely manage an IIS 6.0 server from a Windows XP Professional desktop computer system.

According to Microsoft documentation, “With IIS 6.0 Manager for Windows XP, administrators can remotely manage an IIS 6.0 server from a Windows XP Professional workstation. This tool only installs a snap-in for Microsoft Management Console and its associated DLLs and documentation; it does not install the complete IIS 6.0 server on your local computer”

You can download (3.7 MB) Internet Information Services (IIS) 6.0 Manager for Windows XP from Microsoft web site.

Debian Linux boot disk creation

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Under Debian Linux use mkboot command that makes a bootdisk. mkboot only works on floppy disk drive. By default the bootdisk will use the kernel /vmlinuz and the current root partition. Use the -r option to specify a different partition, and provide the new kernel file directly to specify a different kernel. Use the -d option to specify a different device for the floppy drive.

To create a boot disk of the kernel /vmlinuz:
See kernel version (soft link):

# ls –l /vmlinuz
# mkboot


Insert a floppy diskette into your boot drive, and press .

To use second floppy drive /dev/fd1:

# mkboot -d /dev/fd1

Explain Virtual File System

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Virtual file system (VFS) or Virtual filesystem switch is an abstraction layer on top of a more concrete file system. The purpose of a VFS is to allow for client applications to access different types of concrete file systems in a uniform way. A VFS can for example be used to access local and network storage devices transparently without the client application noticing the difference. Or it can be used to bridge the differences in Windows, Mac OS and Unix filesystems, so that applications could access files on local file systems of those types without having to know what type of file system they’re accessing.

More info about VFS:

Under Linux you can create a Virtual File System as follows
Use dd command to create a VFS disk image (5 MB):
$ dd if=/dev/zero of=/tmp/vfs-disk count=10240
Format your disk image with mkfs.ext3 command:
$ mkfs.ext3 /tmp/vfs-disk
When prompted for confirmation type ‘y’ to format VFS disk image.

Mounting VFS with a loopback device:
# mkdir -p /mnt/vfs0
# mount -o loop=/dev/loop0 /tmp/vfs-disk /mnt/vfs0

It will act as a normal file system. You can take this image to other computer and mount it.

Howto open .daa files (Direct-Access-Archive) under Linux / UNIX

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Q. How do I open .daa file under Linux or UNIX or Windows?

A. You need to use PowerISO for Linux (windows xp/vista/2000 user see below)– This is a free utility for linux which can extract, list, and convert image files (including ISO, BIN, DAA, and other formats). Type “poweriso -? ” for detailed usage information. It is a disk image format that supports advanced features, such as compression, password protection, and splitting to multiple volumes.

Update: Checkout AcetoneISO – a GUI utility for Linux and the disk image emulator that mounts images of DVD and CD media. It can open your .daa file.

Open .daa file – Linux only program

Download poweriso here. Or use wget program:
$ wget
$ tar -zxvf poweriso-1.2.tar.gz
$ ls



Task: list all files and directories in root direcory of /mnt/iso/obsd39/cd39.iso

$ ./poweriso list /mnt/iso/obsd39/cd39.iso /
$ ./poweriso list /mnt/iso/obsd39/cd39.iso / -r

Convert files/directories from .daa image file

Convert image file to other format. For example convert image.daa to standard iso file, enter:
$./poweriso convert image.daa -o image.iso -ot iso

Extract files/directories from image file

Extract all files and directories in root directory of /mnt/iso/obsd39/cd39.iso to /tmp recursively:
$ ./poweriso extract image.iso / -od /tmp

Task: Display help

Type poweriso -? for help:
$ ./poweriso -?

Open daa file – MS Windows only program

You need to use special shareware program called PowerISO to open .daa extension files. This program only works under MS-Windows. See PowerISO web site for more information.

Download PowerISO

Download a free copy of PowerISO (trial version i.e. try it before you purchase software) for MS-Windows.

Is it safe to use hdparm command to get or set hard disk parameters under Linux?

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hdparm command provides a command line interface to various hard disk ioctls supported by the stock Linux ATA/IDE device driver subsystem. Some options may work correctly only with the latest kernels.

Getting hard disk information
You can safely use hdparm to get hard disk information. For example, try out following command to get information about SCSI hard disk (login as the root user):

# hdparm /dev/sda

OR get detailed information:

# hdparm –I /dev/hda



ATA device, with non-removable media
Model Number:       SAMSUNG SP0822N                      
Serial Number:      S06QJ10Y123456   
Firmware Revision:  WA100-31
Used: ATA/ATAPI-6 T13 1410D revision 1
Supported: 7 6 5 4 & some of 7
Logical  max current
cylinders 16383 65535
heads  16 1
sectors/track 63 63
CHS current addressable sectors:    4128705
LBA    user addressable sectors:  156368016
LBA48  user addressable sectors:  156368016
device size with M = 1024*1024:       76351 MBytes
device size with M = 1000*1000:       80060 MBytes (80 GB)
LBA, IORDY(can be disabled)
Queue depth: 1
Standby timer values: spec'd by Standard, no device specific minimum
R/W multiple sector transfer: Max = 16 Current = ?
Recommended acoustic management value: 254, current value: 0
DMA: mdma0 mdma1 mdma2 udma0 udma1 *udma2 udma3 udma4 udma5
    Cycle time: min=120ns recommended=120ns
PIO: pio0 pio1 pio2 pio3 pio4
    Cycle time: no flow control=120ns  IORDY flow control=120ns
Enabled Supported:
NOP cmd
  * Host Protected Area feature set
  * Look-ahead
  * Write cache
  * Power Management feature set
Security Mode feature set
SMART feature set
  * FLUSH CACHE EXT command
  * Mandatory FLUSH CACHE command
  * Device Configuration Overlay feature set
  * 48-bit Address feature set
Automatic Acoustic Management feature set
SET MAX security extension
  * SMART self-test
  * SMART error logging
Master password revision code = 65534
not enabled
not locked
not frozen
not expired: security count
supported: enhanced erase
HW reset results:
CBLID- below Vih
Device num = 1 determined by the jumper
Checksum: correct

You can also find out how fast your hard disk can read or write (cache) data. Run following command 2-3 times to get meaningful results:

# hdparm –tT /dev/hda


Timing cached reads:   1008 MB in  2.00 seconds = 502.96 MB/sec
Timing buffered disk reads:   54 MB in  3.09 seconds =  17.46 MB/sec

Setting hard disk parameters
Setting parameter can be dangerous. Your OS/Linux kernel is optimized to autodetect the correct settings for most hard drives. Do not try to set new values using hdparm command. Wrong parameter may result into loss and/or corruption of data. Read man page of hdparm for all options. You can configure your hard disk using /etc/hdparm.conf under Debian Linux. Under RedHat Linux try /etc/sysconfig/harddisk file.

Caution: Do not modify above files, leave files, as it is unless you know exactly what you are doing.