some question about open fail on /dev/sda nodes
Dear all:
I try to open /dev/sda1 with system call, open(/dev/sda1, O_RDONLY).
But each time it will return negative value, that means fail.
my program is like below:
(gdb) list
1 #includestdio.h
2 #includefcntl.h
3 int main(void)
4 {
5 int fd=0;
6 fd = open(/dev/sda1, O_RDONLY);
7
8 printf(%d\n,fd);
9 }
10
(gdb) b 8
Breakpoint 1 at 0x8048423: file test.c, line 8.
(gdb) r
Starting program: /home/cc/a.out
Breakpoint 1, main () at test.c:8
8 printf(%d\n,fd);
(gdb) p fd
$1 = -1
(gdb)
But I am quite sure I really get /dev/sda1 on my linux system.
below are the dmesg:
$ dmesg |grep sda
[ 4.304624] sd 0:0:0:0: [sda] 117210240 512-byte hardware sectors (60012 MB)
[ 4.304642] sd 0:0:0:0: [sda] Write Protect is off
[ 4.304646] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[ 4.304672] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
enabled, doesn't support DPO or FUA
[ 4.304742] sd 0:0:0:0: [sda] 117210240 512-byte hardware sectors (60012 MB)
[ 4.304757] sd 0:0:0:0: [sda] Write Protect is off
[ 4.304760] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[ 4.304786] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
enabled, doesn't support DPO or FUA
[ 4.304790] sda:4Driver 'sr' needs updating - please use bus_type methods
[ 4.319499] sda1 sda2 sda3 sda56usb 4-2: configuration #1
chosen from 1 choice
[ 4.359729] sda6 sda4
[ 4.359951] sd 0:0:0:0: [sda] Attached SCSI disk
[ 22.637589] EXT3 FS on sda4, internal journal
[ 23.586600] EXT3 FS on sda6, internal journal
$
Does that mean I use the wrong systemcall or we cannot open /dev/sda1 like this?
appreciate your help,
miloody
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Re: some question about open fail on /dev/sda nodes
On Sun, Aug 16, 2009 at 3:09 PM, loodymilo...@gmail.com wrote:
Dear all:
I try to open /dev/sda1 with system call, open(/dev/sda1, O_RDONLY).
But each time it will return negative value, that means fail.
Have you checked for the errno ? I guess it is permission denied.
/home/mkatiyar dd if=/dev/sda1 of=/dev/zero
dd: opening `/dev/sda1': Permission denied
Thanks -
Manish
my program is like below:
(gdb) list
1 #includestdio.h
2 #includefcntl.h
3 int main(void)
4 {
5 int fd=0;
6 fd = open(/dev/sda1, O_RDONLY);
7
8 printf(%d\n,fd);
9 }
10
(gdb) b 8
Breakpoint 1 at 0x8048423: file test.c, line 8.
(gdb) r
Starting program: /home/cc/a.out
Breakpoint 1, main () at test.c:8
8 printf(%d\n,fd);
(gdb) p fd
$1 = -1
(gdb)
But I am quite sure I really get /dev/sda1 on my linux system.
below are the dmesg:
$ dmesg |grep sda
[ 4.304624] sd 0:0:0:0: [sda] 117210240 512-byte hardware sectors (60012
MB)
[ 4.304642] sd 0:0:0:0: [sda] Write Protect is off
[ 4.304646] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[ 4.304672] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
enabled, doesn't support DPO or FUA
[ 4.304742] sd 0:0:0:0: [sda] 117210240 512-byte hardware sectors (60012
MB)
[ 4.304757] sd 0:0:0:0: [sda] Write Protect is off
[ 4.304760] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[ 4.304786] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
enabled, doesn't support DPO or FUA
[ 4.304790] sda:4Driver 'sr' needs updating - please use bus_type
methods
[ 4.319499] sda1 sda2 sda3 sda56usb 4-2: configuration #1
chosen from 1 choice
[ 4.359729] sda6 sda4
[ 4.359951] sd 0:0:0:0: [sda] Attached SCSI disk
[ 22.637589] EXT3 FS on sda4, internal journal
[ 23.586600] EXT3 FS on sda6, internal journal
$
Does that mean I use the wrong systemcall or we cannot open /dev/sda1 like
this?
appreciate your help,
miloody
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unsubscribe kernelnewbies to ecar...@nl.linux.org
Please read the FAQ at http://kernelnewbies.org/FAQ
--
Thanks -
Manish
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Re: some question about open fail on /dev/sda nodes
You can print a human readable string for error using 'strerror' function.
see -
man strerror
man errno
--
Thanks,
- John
On 08/16/2009 04:09 PM, Manish Katiyar wrote:
On Sun, Aug 16, 2009 at 3:09 PM, loodymilo...@gmail.com wrote:
Dear all:
I try to open /dev/sda1 with system call, open(/dev/sda1, O_RDONLY).
But each time it will return negative value, that means fail.
Have you checked for the errno ? I guess it is permission denied.
/home/mkatiyar dd if=/dev/sda1 of=/dev/zero
dd: opening `/dev/sda1': Permission denied
Thanks -
Manish
my program is like below:
(gdb) list
1 #includestdio.h
2 #includefcntl.h
3 int main(void)
4 {
5 int fd=0;
6fd = open(/dev/sda1, O_RDONLY);
7
8printf(%d\n,fd);
9 }
10
(gdb) b 8
Breakpoint 1 at 0x8048423: file test.c, line 8.
(gdb) r
Starting program: /home/cc/a.out
Breakpoint 1, main () at test.c:8
8printf(%d\n,fd);
(gdb) p fd
$1 = -1
(gdb)
But I am quite sure I really get /dev/sda1 on my linux system.
below are the dmesg:
$ dmesg |grep sda
[4.304624] sd 0:0:0:0: [sda] 117210240 512-byte hardware sectors (60012 MB)
[4.304642] sd 0:0:0:0: [sda] Write Protect is off
[4.304646] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[4.304672] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
enabled, doesn't support DPO or FUA
[4.304742] sd 0:0:0:0: [sda] 117210240 512-byte hardware sectors (60012 MB)
[4.304757] sd 0:0:0:0: [sda] Write Protect is off
[4.304760] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[4.304786] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
enabled, doesn't support DPO or FUA
[4.304790] sda:4Driver 'sr' needs updating - please use bus_type methods
[4.319499] sda1 sda2 sda3 sda56usb 4-2: configuration #1
chosen from 1 choice
[4.359729] sda6 sda4
[4.359951] sd 0:0:0:0: [sda] Attached SCSI disk
[ 22.637589] EXT3 FS on sda4, internal journal
[ 23.586600] EXT3 FS on sda6, internal journal
$
Does that mean I use the wrong systemcall or we cannot open /dev/sda1 like this?
appreciate your help,
miloody
--
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unsubscribe kernelnewbies to ecar...@nl.linux.org
Please read the FAQ at http://kernelnewbies.org/FAQ
Re: some question about open fail on /dev/sda nodes
Resending
On Sun, Aug 16, 2009 at 7:38 PM, Siddu siddu.s...@gmail.com wrote:
On Sun, Aug 16, 2009 at 3:09 PM, loody milo...@gmail.com wrote:
Dear all:
I try to open /dev/sda1 with system call, open(/dev/sda1, O_RDONLY).
But each time it will return negative value, that means fail.
my program is like below:
(gdb) list
1 #includestdio.h
2 #includefcntl.h
3 int main(void)
4 {
5 int fd=0;
6fd = open(/dev/sda1, O_RDONLY);
7
8printf(%d\n,fd);
9 }
10
(gdb) b 8
Breakpoint 1 at 0x8048423: file test.c, line 8.
(gdb) r
Starting program: /home/cc/a.out
Breakpoint 1, main () at test.c:8
8printf(%d\n,fd);
(gdb) p fd
$1 = -1
(gdb)
But I am quite sure I really get /dev/sda1 on my linux system.
below are the dmesg:
$ dmesg |grep sda
[4.304624] sd 0:0:0:0: [sda] 117210240 512-byte hardware sectors
(60012 MB)
[4.304642] sd 0:0:0:0: [sda] Write Protect is off
[4.304646] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[4.304672] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
enabled, doesn't support DPO or FUA
[4.304742] sd 0:0:0:0: [sda] 117210240 512-byte hardware sectors
(60012 MB)
[4.304757] sd 0:0:0:0: [sda] Write Protect is off
[4.304760] sd 0:0:0:0: [sda] Mode Sense: 00 3a 00 00
[4.304786] sd 0:0:0:0: [sda] Write cache: enabled, read cache:
enabled, doesn't support DPO or FUA
[4.304790] sda:4Driver 'sr' needs updating - please use bus_type
methods
[4.319499] sda1 sda2 sda3 sda56usb 4-2: configuration #1
chosen from 1 choice
[4.359729] sda6 sda4
[4.359951] sd 0:0:0:0: [sda] Attached SCSI disk
[ 22.637589] EXT3 FS on sda4, internal journal
[ 23.586600] EXT3 FS on sda6, internal journal
$
Does that mean I use the wrong systemcall or we cannot open /dev/sda1 like
this?
appreciate your help,
miloody
Try to run the following code as root and also as normal user . You ll see
the difference
#include stdio.h
#include fcntl.h
int main ( int argc , char *argv[] ) {
int fd = 0;
fd = open( /dev/sda1 , O_RDONLY );
if ( fd == -1 ) {
perror( The System Error Message was );
}
else {
printf(The File Descriptor is : %d \n, fd );
}
return 0;
}
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Please read the FAQ at http://kernelnewbies.org/FAQ
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Regards,
~Sid~
--
Regards,
~Sid~
