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 http://poweriso.com/poweriso-1.2.tar.gz
$ 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.

Linux Boot Disk under Redhat or Fedora Linux

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Q: How do I create a boot disk under RedHat or Fedora Linux distributions.

A: You need to use mkbootdisk command to creates a stand-alone boot disk floppy for the running system. This command works under both Red Hat Linux /RHEL and Fedora Linux.
This command creates a boot floppy appropriate for the running system or kernel. The boot disk is entirely self-contained, and includes an initial ramdisk image which loads any necessary SCSI modules for the system. The created boot disk looks for the root filesystem on the device suggested by /etc/fstab. The only required argument is the kernel
version to put onto the boot floppy.

(a) Put a floppy disk into drive

(b) Type following command to create a boot disk:

# mkbootdisk $(uname -r)


Insert a disk in /dev/fd0. Any information on the disk will be lost.
Press  to continue or ^C to abort:

(c) If you would like to use second floppy disk then use command as follows:

# mkbootdisk –device /dev/fd1 $(uname -r)

(d) You can also instructs this command to make a bootable ISO image as devicefile:

# mkbootdisk –iso $(uname -r)

Then you can burn ISO image to CDR/CDRW.

Will Microsoft office and other Windows applications be able to run on my Linux distribution?

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Short answer is yes. To be frank it depends upon the application. Popular Windows application can be run using Wine software under Linux (and UNIX like oses). Wine project aims to allow a PC running a Unix/Linux like operating system and the X Window System to execute x86 programs for Microsoft Windows.

Wine can run many popular windows application such as MS-Office, Dreamweaver, Internet Explorer 5.5+, Adobe Photoshop 7, Illustrator 9, Acrobat Reader etc. See complete list of supported applications.

CrossOver Office is a commercial program of Wine software that allows many Windows-based applications to run on Linux. The actively-supported applications include Microsoft Office 2003, XP, 2000 and 97, Microsoft Internet Explorer 6, Macromedia Dreamweaver MX, Macromedia Flash MX, Adobe Photoshop, Lotus Notes and Quicken. A full list of application is available from CodeWeavers web site.

Other choice is to use VMware software on top of Linux, which allows to install Windows (and other operating systems) and its application inside virtual machine. VMware Workstation is one of the commercial software products sold by VMware Inc. The Workstation software consists of a virtual machine suite for Intel x86-compatible computers, which allows the creation and execution of multiple x86 virtual computers simultaneously.

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