C++ Code to Access Linux Hard Disk Sectors (with a LoopBack Virtual Hard Disk)
Hi all,
I'm kind of new to programming in Linux & c/c++. I'm currently writing a FileManager using Ubuntu Linux(10.10) for Learning Purposes. I've got started on this project by creating a loopback device to be used as my virtual hard disk. After creating the loop back hard disk and mounting it has the following configuration.
Now what I want to do is develop a c++ program to read & write files to this loop back device,which I'm using to simulate an actual hard disk,at the blocks & sectors level. So far I've come up with the following code. But I'm still unable to read files from the hard disk one block at a time.
When I run this Program All what I get is the message for NULL.
"Error In Opening the HardDisk File Retuning Error...".
Could you please help me by pointing what am I doing wrong here ?. So I could open the loopback device as a file an access it at the sectors & block level.
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When we write a programme,we declare variables and compiler allocates memory to them.I want to get access to the physical block number of hard-disk where actually the data is stored by the programme "
Some one help me out... (1 Reply)
When we write a programme,we declare variables and compiler allocates memory to them.I want to get access to the physical block number of hard-disk where actually the data is stored by the programme "
Some one help me out... (3 Replies)
Discussion started by: nagraz007
3 Replies
LEARN ABOUT SUNOS
prtvtoc
prtvtoc(1M) System Administration Commands prtvtoc(1M)NAME
prtvtoc - report information about a disk geometry and partitioning
SYNOPSIS
prtvtoc [-fhs] [-t vfstab] [-m mnttab] device
DESCRIPTION
The prtvtoc command allows the contents of the label to be viewed. The command can be used only by the super-user.
The device name can be the file name of a raw device in the form of /dev/rdsk/c?t?d?s2 or can be the file name of a block device in the
form of /dev/dsk/c?t?d?s2.
OPTIONS
The following options are supported:
-f Report on the disk free space, including the starting block address of the free space, number of blocks, and unused parti-
tions.
-h Omit the headers from the normal output.
-m mnttab Use mnttab as the list of mounted filesystems, in place of /etc/mnttab.
-s Omit all headers but the column header from the normal output.
-t vfstab Use vfstab as the list of filesystem defaults, in place of /etc/vfstab.
EXAMPLES
Example 1: Using the prtvtoc Command
The following example uses the prtvtoc command on a 424-megabyte hard disk:
example# prtvtoc /dev/rdsk/c0t3d0s2
* /dev/rdsk/c0t3d0s2 partition map
*
* Dimension:
* 512 bytes/sector
* 80 sectors/track
* 9 tracks/cylinder
* 720 sectors/cylinder
* 2500 cylinders
* 1151 accessible cylinders
*
* Flags:
* 1: unmountable
* 10: read-only
* * First Sector Last
* Partition Tag Flags Sector Count Sector Mount Directory
0 2 00 0 76320 76319 /
1 3 01 76320 132480 208799
2 5 00 0 828720 828719
5 6 00 208800 131760 340559 /opt
6 4 00 340560 447120 787679 /usr
7 8 00 787680 41040 828719 /export/home
example#
The data in the Tag column above indicates the type of partition, as follows:
Name Number
UNASSIGNED 0x00
BOOT 0x01
ROOT 0x02
SWAP 0x03
USR 0x04
BACKUP 0x05
STAND 0x06
VAR 0x07
HOME 0x08
ALTSCTR 0x09
CACHE 0x0a
RESERVED 0x0b
The data in the Flags column above indicates how the partition is to be mounted, as follows:
Name Number
MOUNTABLE, READ AND WRITE 0x00
NOT MOUNTABLE 0x01
MOUNTABLE, READ ONLY 0x10
Example 2: Using the prtvtoc Command with the -f Option
The following example uses the prtvtoc command with the -f option on a 424-megabyte hard disk:
example# prtvtoc -f /dev/rdsk/c0t3d0s2
FREE_START=0 FREE_SIZE=0 FREE_COUNT=0 FREE_PART=34
Example 3: Using the prtvtoc Command on a Disk Over One Terabyte
The following example uses uses the prtvtoc command on a disk over one terabyte:.
example# prtvtoc /dev/rdsk/c1t1d0s2
* /dev/rdsk/c1t1d0s2 partition map
*
* Dimensions:
* 512 bytes/sector
* 3187630080 sectors
* 3187630013 accessible sectors
*
* Flags:
* 1: unmountable
* 10: read-only
*
* First Sector Last
* Partition Tag Flags Sector Count Sector Mount Directory
0 2 00 34 262144 262177
1 3 01 262178 262144 524321
6 4 00 524322 3187089340 3187613661
8 11 00 3187613662 16384 318763004
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
+-----------------------------+-----------------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+-----------------------------+-----------------------------+
|Availability |SUNWcsu |
+-----------------------------+-----------------------------+
SEE ALSO devinfo(1M), fmthard(1M), format(1M), mount(1M), attributes(5)WARNINGS
The mount command does not check the "not mountable" bit.
SunOS 5.10 25 Jul 2002 prtvtoc(1M)