using mount command within a c program

[diegos]

Hi,

I want to use the mount command from a c program running in a linux machine with 2.6.18 kernel. I want to use it to mount a file system via nfs.

I have tried the umount2 command and it works but the mount command throws an error : Invalid argument.

Sure i'm doing something wrong but i need help because i can't find any example of a c-programm using this function with nfs.

mount( "server's ip address:/nameofdirectory", "/mnt", "nfs", 0, "");

and /mnt is a directory existing in my local file system.

Any advice??

Thanks in advance

[gerard4143]

Try info/man system, this should allow you to execute the shell commands "mount/umount" from your program...Gerard4143

[BharathShankar]

Try popen() call to execute the mount command.

[Lakshmipathi]

Hi diegos,
Is nfs demaon running in your machine ?
If so,first try to mount using mount command.

If above works fine,try posting out of

strace your_executable.

[diegos]

Hi Lakshmipathi,

Yes, nfs daemon is running and if I run

mount -t nfs 172.20.41.173:/server /mnt

it works without problem and i can see the remote directory.

The result of strace ./pruebamount is:

execve("./pruebamount", ["./pruebamount"], [/* 17 vars */]) = 0
uname({sys="Linux", node="srvInstPreprod", ...}) = 0
brk(0) = 0x804a000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
mmap2(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f18000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=21956, ...}) = 0
mmap2(NULL, 21956, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7f12000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/tls/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\2 40O\1"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0644, st_size=1245488, ...}) = 0
mmap2(NULL, 1251484, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7de0000
mmap2(0xb7f08000, 28672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x12 = 0xb7f08000
mmap2(0xb7f0f000, 10396, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7f0f000
close(3) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7ddf000
mprotect(0xb7f08000, 20480, PROT_READ) = 0
set_thread_area({entry_number:-1 -> 6, base_addr:0xb7ddf8e0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
munmap(0xb7f12000, 21956) = 0
mount("172.20.41.173:/server", "/mnt", "nfs", 0, "") = -1 EINVAL (Invalid argument)
fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7f17000
write(1, "mensaje_error 22 Invalid argumen"..., 34mensaje_error 22 Invalid argument
) = 34
munmap(0xb7f17000, 4096) = 0
exit_group(34) = ?
Process 14103 detached

I would prefer to use this function instead of the popen or system call because i think (i'm not sure if it's true) that i could be able to have a better control of the execution.

Thanks in advance for your help and attention.

[Lakshmipathi]

Try to fill the last argument as rw or ro and check again.

mount( "server's ip address:/nameofdirectory", "/mnt", "nfs", 0, "rw");

EINVAL denotes invalid parameter is passed.So it can be fixed.

[diegos]

I've tried changing the last argument to "rw", "ro" but it remains with the same error.

it could be the syntax of ip address:/nameofdirectory that it's wrong??

I can't find any example of a c program making a call to mount() as i'm trying to do.

Thanks for your replies

[Lakshmipathi]

one suggestion ,from another forum:

mount(need to be mounted,"point mount path,flag,"MNT_RDONLY");

code mount in c language - Page 2 - High Level Programming - The UNIX and Linux Forums


and this another - Seems like you need to fill struct and pass it

Re: [gentoo-user] mount nfs thru mount system call

I'm not sure which is correct-just try them-Though i used mount() sys.call but never tried it with NFS.So curious about
the solution.

Let me know the results

[diegos]

i'm still with more or less the same error.

Now, following my code is:

#include <stdio.h>
#include <errno.h>
#include <sys/socket.h>
#include <linux/mount.h>
#include <linux/nfs.h>
#include <linux/nfs_mount.h>
#include <sys/param.h>

main (int argc, char *argv[]) {


/*struct nfs_mount_data data;*/
struct nfs2_fh estruc1;
struct sockaddr_in estruc2;
struct nfs3_fh estruc3;
struct nfs_mount_data data={4,
1,
estruc1,
1,
4096,
4096,
1000,
3,
1,
1,
1,
1,
estruc2,
"172.20.41.173",
17,
1,
estruc3,
4,
""};


mount("172.20.41.173:/server", "/mnt", "nfs", 0 , data);
/*
mount("172.20.41.173:/server", "/mnt", "nfs", 0 , "rsize=4096,wsize=4096");
*/
printf("mensaje_error %d %s\n",errno, strerror(errno));
}

But the strace ....

execve("./kk", ["./kk"], [/* 17 vars */]) = 0
uname({sys="Linux", node="srvInstPreprod", ...}) = 0
brk(0) = 0x804a000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
mmap2(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7fab000
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY) = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=21956, ...}) = 0
mmap2(NULL, 21956, PROT_READ, MAP_PRIVATE, 3, 0) = 0xb7fa5000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
open("/lib/tls/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\2 40O\1"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0644, st_size=1245488, ...}) = 0
mmap2(NULL, 1251484, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xb7e73000
mmap2(0xb7f9b000, 28672, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x12 = 0xb7f9b000
mmap2(0xb7fa2000, 10396, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xb7fa2000
close(3) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7e72000
mprotect(0xb7f9b000, 20480, PROT_READ) = 0
set_thread_area({entry_number:-1 -> 6, base_addr:0xb7e728e0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0
munmap(0xb7fa5000, 21956) = 0
mount("172.20.41.173:/server", "/mnt", "nfs", 0, umovestr: Input/output error
0x4) = -1 EFAULT (Bad address)
fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 0), ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xb7faa000
write(1, "mensaje_error 14 Bad address\n", 29mensaje_error 14 Bad address
) = 29
munmap(0xb7faa000, 4096) = 0
exit_group(29) = ?
Process 13592 detached

With the string "rsize=4096,wsize=4096" instead of data, it does the same.

I'm begining to be run out of ideas...

Any other idea??

thanks

[diegos]

The last thing I've tried was:

struct nfs2_fh estruc1={""};
struct sockaddr_in estruc2; //={AF_INET,0};
struct nfs3_fh estruc3={0,""};
struct nfs_mount_data data={3, /* version */
1, /* fd */
estruc1,
1, /* flags */
4096, /* rsize */
4096, /* wsize */
1000, /* timeo */
3, /* retrans */
3, /* acregmin */
60, /* acregmax */
30, /* acdirmin */
60, /* acdirmax */
estruc2,
"172.20.41.173", /* hostname */
14, /* namelen */
1, /* bsize */
estruc3,
4,
""};

const char *remoto = "172.20.41.173:/server";
const char *puntomontaje = "/mnt";
const char *tipomontaje = "nfs";
unsigned long int flags = MS_RDONLY;
int flags_umount = 0;

int error;

if (mount(remoto, puntomontaje, tipomontaje, flags, &data) == 0) {
printf("Se ha montado correctamente\n");
} else {
printf("No se ha podido montar.");
switch(errno){
case EBUSY: printf("Ya esta montado\n"); break;
case EINVAL: printf("einval\n"); break;
default: break;
}
}

In certain moment, it worked! but i've tried to repeat it without success. Really, i don't known the detailed meaning of the nfs_mount_data structure... Any help??

it would be very helpful if i find an example of c program using this.

thanks in advance