Programming :: C Program - Getting The Raw Size Of A Block Device
Oct 16, 2010
How do you go about getting the raw size of a block device under Linux from within a C program? And I mean the raw size of the block device itself, not a file system that may or may not be installed on it. And I'd like to be able to get the raw size of any block device, from hard drives (e.g., /dev/sda) to LVM partitions (/dev/mapper/vg0-home) to loop devices to anything else that is a Linux block device.
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May 11, 2011
I have one hard disk (call her HDA) that contains nothing but a single ext4 partition containing a backup of all my important data. Last night I did a clean install of Ubuntu 10.10 on my primary hard disk (call her HDB) and from there proceeded to upgrade directly to Ubuntu 11.04 upgrade. In 10.10, I was able to read HDA just fine. However after the upgrade, I can no longer mount this drive. When mounting from file browser:
Code:
Error mounting: mount: wrong fs type, bad option, bad superblock on /dev/sda,missing codepage or helper program, or other error In some cases useful info is found in syslog - try dmesg | tail or so The end of dmesg said the following:
Code:
dmesg | tail
[ 82.130904] EXT4-fs (sda): bad geometry: block count 122096646 exceeds size of device (122096381 blocks)
my hard disk has a block count greater than the size of my device. I've done my background searching on this and tried a command line utility I've never heard of before:
Code:
# sudo e2fsck /dev/sda
e2fsck 1.41.14 (22-Dec-2010)
The filesystem size (according to the superblock) is 122096646 blocks
The physical size of the device is 122096381 blocks
[code]....
this is as far as I've gotten. This drive holds over a decade's worth of work for me and is extremely valuable. I really didn't think that the Ubuntu upgrade process would mess with this drive, seeing as the Ubuntu install was contained on an entirely different drive. What is it that I need to do to restore my drive to working status?
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Jul 12, 2011
Here [URL].. it says that you need to provide a block size to open an archive. What does that mean, and what would be a good number to use?
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Nov 30, 2010
Is there an easy example of a block device driver I could follow as a guide to write my own module?
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Feb 13, 2009
I'm setting up a machine that's going to be used to test randomly connected tape drives one at a time, and as such, I'm writing the test routine using mt in a bash script, for user-friendliness. The problem is the block device name changes on occasion as tape drives are swapped out and busses are rescanned, so I can't "hard code" a block name into the script.
I know programs like lsscsi and hwinfo will give you block device names as part of their output, but I can't seem to grep anything in such a way as to have the final output be just the block name (ie /dev/st2, or optimally 'st2'), so that I can just have the script read said output, and drop it into the necessary variable.
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Nov 1, 2010
I have a write call to a ttyACM serial device that blocks after several hundreds bytes are written.I'm writing in ~25 byte chunks, so I have 5-8 successful writes, then the next write blocks forever.I can bypass the blocked call using select, but I can never call write again without closing and re-opening the port.
The serial port is opened correctly because I can read from it just fine. Write permissions are correct, and it's opened RW.The code is likely correct because I tested the same code using the same device on a pure RS-232 serial port, and it worked fine - no block. Is there anything to know about the linux ACM module?It's my understanding that write calls basically shouldn't block.They're supposed to return -1 if there's an error.
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Apr 15, 2011
I am trying to run C++ program on linux.
My program consume a lot of memory so that the memory is used up fast and memory swap is very high.
I can find this by "ps" .
My program is long.
I need to find out which part of my program consume so much memory ?
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Jul 14, 2010
I am writing a program in C to create a GUI application using GTK 2. My actual program is quite large, so I am using a modified version of the sample program from GNOME library for trial. I wish to increase the font size, and I have using PangoFontDescription. I have made that section of the code bold and italic below for quick reference to the code that affects fonts. But it does not make any difference. I am compiling the C file using gcc. The code is as follows(hello.c):
#include <gtk/gtk.h>
#include <glib.h>
#include <gdk/gdk.h>
[code]....
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Aug 1, 2010
you have to read from many devices separate devices and make it look like a single one. It sounds very much like a device driver to me, perhaps... but getting my hands dirty with kernel code sounds like a daunting task for me that I've never done it...
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Apr 27, 2011
i am trying learn to program linux kernel modules and smoothly transition in device driver programming. I have a year and a half worth of programming in C and have been using linux for years!! But my question is how do i compile a module? I got as far as coding it but am stuck as of now.
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Mar 1, 2010
In a book, I read tha cmchk command is used to get the disk block size. But in Ubuntu, it is not allowed as command is not available.Can some body tell me what is its equivalent in Ubuntu.
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Nov 24, 2010
Does anyone have a guide/instructions to change the Block Size on a Linux disk from 4096 bytes to 1mb or more?
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Aug 20, 2011
i'm calculating the size of directories using "du"
PHP: function du($path)
{
exec ('du -sb ' . $path, $res[]);
$size = $res[0][0];
[Code].....
But then again, it doesn't calculate the actual file size, but rather a size aligned to 1024 bytes just as Windows does that with 4096 bytes cluster size. Is there a way to calculate the actual file size? eg. 1021 bytes
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Mar 8, 2010
I'm trying trying to understand dd, and I'd like to know why frequently do we have to use a block read/write size, like "dd bs=1024", "dd ibs=512"... If it executes the operation byte by byte, isn't it irrelevant? What is this block size then?
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Jan 17, 2011
I use dd in its simplest form to clone a hard drive dd if=INPUT of=OUTPUT However, I read in the manpage that dd knows a blocksize parameter. I was wondering whether there is an optimal value for the blocksize parameter that will speed up the cloning procedure?
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Feb 5, 2011
I am doing some benchmarking on EXT4 performance on Compact Flash media. I have created an ext4 fs with block size of 65536. however I cannot mount it on ubuntu-10.10-netbook-i386. (it is already mounting ext4 fs with 4096 bytes of block sizes) According to my readings on ext4 it should allow such big block sized fs. I want to hear your comments.
[Code]...
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Mar 31, 2010
I have reformatted my hard drive with allocation size 64K for a better performance on my WDTV HD media player(dealing with large files). When I mount this drive on Linux, the mount tells me that "blksize=4096".If I keep writing files usinghis default etting(blksize=4096) to my NTFS formatted hard drive, will my WDTV be able to benefit from the performance improvement of 64k allocation size ? Should I try and mount my hard drive with a larger blksize ?I did some research on google but couldn't find an option to increase the blksize when mounting an NTFS pre-formatted drive.
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Apr 8, 2011
what block size means in plain English? I know block size 4k has 2 TB of file size limit and 1024 has around 17 GB. How do they calculate this?
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Mar 31, 2010
I have reformatted my hard drive with allocation size 64K(formatted on windows with 64k setting) for a better performance on my WDTV HD media player(dealing with large files).When I mount this drive on Linux, the properties tells me that"blksize=4096".If I keep writing files using this default setting(blksize=4096) to my NTFS formatted hard drive, will my WDTV be able to benefit from the performance improvement of 64k allocation size ?I am confused, Does it have anything to do with "blksize=4096". ?Should I try and mount my hard drive with a larger blksize ?I did some research on google but couldn't find an option to increase the blksize when mounting an NTFS pre-formatted drive
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Mar 4, 2010
I want to generate a temporary random list from a directory of files and then determine the size of an arbitrary block of files from this list (say 1-25 or 26-50) and add their names to a file along with some other info for each name. I can generate a random list with file sizes like this: ls -l | sort -R | cut -d " " -f 6 but i'm not sure how to add up the sizes of just a certain block of these files and at the same time save the file names.
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Apr 7, 2010
I have an external hard disk drive and I would like it to be recognized with the same name (e.g. /dev/sbd) after each boot.
Is there any way to make that?
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Jun 1, 2010
I want to test LVM+Raid. When I was testing ZFS on Solaris, I was able to create regular files, and use those as disks for testing.I tried creating a regular file full of zeros w/ dd, then partitioning that. fdisk seemed to be able to create a partition on the regular file, but mkfs and parted couldn't work with it. Is there any way to create fake block devices for testing?
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Jun 14, 2010
When I try to mount the /dev/sdd1 device then it give errormount -t ext3 /dev/sdd1 /4hdmount:/dev/sdd1 is not a valid block device
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Apr 25, 2010
I created LVM and formatted it. But at the time of mounting it getting this error message ".....not a block device".
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Jun 10, 2010
depending on reading some apparmor docs, I know that apparmor read logs to determine what profile a program will be, that means a profile only can be built when the program have been exec at least a time, or we already how will be executed of a specific program. but if a hack inserts a bad-program such as a back door or virus what should never be executed any time, and at the same time we don't know what's the consequence will happen due to the behaviors of a bad-program. therefore, how could apparmor do to prevent these situations? Can apparmor confine every thing what under a specific directory by default? because use: aa-autodep /path/to/restrict/* is 'complain' by default and everything are allowed, can apparmor deny everything by default?
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Apr 22, 2010
Is it possible somehow to block some bluetooth device with specif address (mac) ?
(like iptables block by mac)?
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Jan 19, 2011
I built a Raid5 volume with 3 SATA II hard disk drives. Further I have a system disk conected through IDE. During the first setup the IDE disk becomes sda, the SATA II disk sd[bcd] respectively. Now, sometimes the device names change after reboot - why ever... E.g. one of the raid5 disk become sda and so I got an error message during the boot procedure regarding the raid set. Curious, when the system is up and I stop and restart the Raid5 volume it comes up and runs fine. Because I'm currently at work I can't post any more detailed config files at the moment.
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Jul 4, 2011
I am trying to debug the issue of a desktop that has for the last two weeks started having kernel panics at boot time. This machine has been running flawlessly for the last 8 years, and has had three OS upgrades. I am using memtest to try to understand the issue. The following is part of the memtest output: Reading all physical volumes Buffer I/O error device hdc logical block 0 Buffer I/O error device hdc logical block 15
Illegal node for this track or incompatible media (asc=0x64 ascq=0x00) The failed "Read 10" packet command was /dev/hdc: read failed after 0 of 4096 at 0 Input/output error and similar set of mesaages After this udev checks correctly, and hardware, storage and audio are initialized However sometime in the middle of the boot process, a kernel panic occurs with message Kernel panic -- not symcing : Fatal exception in interrupt
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Nov 2, 2009
* I am implementing mass storage device on a test board.
* It contains NAND flash.
* Using corresponding "udc driver" and "g_file_storage" I could make my test board enumerate as mass storage device on my Linux machine.
* my 16 MB pen drive (test board) is now ready for read/write.
But there are some Bad Blocks on the NAND.Hence copy is not complete. Although on Linux machine there is no error message. Now , what is there in a normal pen drive which manages the Bad Block or what am I missing so that such Bad Blocks are managed.
Here is the error I get on my test board :
mtdblock: erase of region [0x2c0000, 0x4000] on "Bon 2" failed
end_request: I/O error, dev mtdblock2, sector 5664
Buffer I/O error on device mtdblock2, logical block 708
[code]....
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Mar 15, 2011
I want to keet some data on windows dir. I have tried the below command and giving the below error.
[root@xyz0044 ~]# mount -t cifs //10.48.64.52/jata -o username=domainv.kumar3,password=xxxx /mnt/backup
mount: block device //10.48.64.52/jata is write-protected, mounting read-only
mount: cannot mount block device //10.48.64.52/jata read-only
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