Question:
In C/C++/C#. (I need it for C#, but C and C++ is also fine).
How can I do a mount -a on Linux. I mean programmatically, without starting a process like
system("mount -a");
Edit:
Note the "-a".
My question is not actually about how to mount A mountpoint.
It's about how to mount ALL mountpoints in /etc/fstab.
That means parsing the file, extracting the mountpoints, check if already mounted, and only if not already mounted, mount...
Check out the man page by typing man 2 mount. It talks about a system call that can avoid the actual use of system():
#include <sys/mount.h>
int mount(const char *source, const char *target, const char *filesystemtype,
unsigned long mountflags, const void *data);
@Ignacio Vazquez-Abrams: About your "no way to perform this in C#" ...
Proof that you're wrong by contradiction:
The bellow code is capable of doing the same as
(apt-get install jfsutils)
dd if=/dev/zero of=jfs.dsk bs=1048576 count=150
mkfs.jfs -O jfs.dsk
mkdir -p /mnt/jfs
mount /volumes/jfs.dsk /mnt/jfs -t jfs -o loop
umount /mnt/jfs/
Code:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace Syscalls
{
public class Linux
{
// apt-get source util-linux
// ./mount/loop.h
// ./mount/mount.c
// ./mount/lomount.c
// ./include/linux_version.h
// ./lib/linux_version.c
// ./include/linux_reboot.h
protected const int LOOP_SET_FD = 0x4C00;
protected const int LOOP_CLR_FD = 0x4C01;
protected const int LOOP_GET_STATUS = 0x4C03;
protected const int LOOP_SET_STATUS = 0x4C02;
protected const int LOOP_GET_STATUS64 = 0x4C05;
protected const int LOOP_SET_STATUS64 = 0x4C04;
protected const int LO_NAME_SIZE = 64;
protected const int LO_KEY_SIZE = 32;
protected const int PATH_MAX = 4096;
// MS_RELATIME //(default for Linux >= 2.6.30)
// MS_STRICTATIME //(default for Linux < 2.6.30)
// http://harmattan-dev.nokia.com/docs/library/html/manpages/headers/sys/mount.html
public enum MountFlags : ulong
{
MS_RDONLY = 1, // Mount read-only.
MS_NOSUID = 2, // Ignore suid and sgid bits.
MS_NODEV = 4, // Disallow access to device special files.
MS_NOEXEC = 8, // Disallow program execution.
MS_SYNCHRONOUS = 16, // Writes are synced at once.
MS_REMOUNT = 32, // Alter flags of a mounted FS.
MS_MANDLOCK = 64, // Allow mandatory locks on an FS.
S_WRITE = 128, // Write on file/directory/symlink.
S_APPEND = 256, // Append-only file.
S_IMMUTABLE = 512, // Immutable file.
MS_NOATIME = 1024, // Do not update access times.
MS_NODIRATIME = 2048, // Do not update directory access times.
MS_BIND = 4096, // Bind directory at different place.
}; // End Enum MountFlags : ulong
/*
// http://unix.superglobalmegacorp.com/Net2/newsrc/sys/fcntl.h.html
[Flags]
protected enum OpenFlags : int
{
// open-only flags
O_RDONLY = 0x0000, // open for reading only
O_WRONLY = 0x0001, // open for writing only
O_RDWR = 0x0002, // open for reading and writing
O_ACCMODE = 0x0003, // mask for above modes
//#ifdef KERNEL
FREAD = 0x0001,
FWRITE = 0x0002,
//#endif
O_NONBLOCK = 0x0004, // no delay
O_APPEND = 0x0008, // set append mode
//#ifndef _POSIX_SOURCE
O_SHLOCK = 0x0010, // open with shared file lock
O_EXLOCK = 0x0020, // open with exclusive file lock
O_ASYNC = 0x0040, // signal pgrp when data ready
O_FSYNC = 0x0080, // synchronous writes
//#endif
O_CREAT = 0x0200, // create if nonexistant
O_TRUNC = 0x0400, // truncate to zero length
O_EXCL = 0x0800, // error if already exists
//#ifdef KERNEL
FMARK = 0x1000, // mark during gc()
FDEFER = 0x2000, // defer for next gc pass
FHASLOCK = 0x4000 // descriptor holds advisory lock
} // End Enum OpenFlags : int
*/
[System.Runtime.InteropServices.StructLayout(System.Runtime.InteropServices.LayoutKind.Sequential)]
protected struct loop_info
{
public int lo_number;
public System.UIntPtr lo_device; //my_dev_t lo_device; // my_dev_t: long unsigned int
public System.UIntPtr lo_inode; //unsigned long lo_inode;
public System.UIntPtr lo_rdevice; //my_dev_t lo_rdevice;// my_dev_t: long unsigned int
public int lo_offset;
public int lo_encrypt_type;
public int lo_encrypt_key_size;
public int lo_flags;
[System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst = LO_NAME_SIZE)]
public string lo_name; //char lo_name[LO_NAME_SIZE];
[System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst = LO_KEY_SIZE)]
public string lo_encrypt_key; //unsigned char lo_encrypt_key[LO_KEY_SIZE];
[System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValArray, SizeConst = 2)]
public System.UIntPtr[] lo_init; //unsigned long lo_init[2];
[System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst = 4)]
public string reserved; //char reserved[4];
}; // End Struct loop_info
protected struct loop_info64
{
public System.UInt64 lo_device;
public System.UInt64 lo_inode;
public System.UInt64 lo_rdevice;
public System.UInt64 lo_offset;
public System.UInt64 lo_sizelimit; /* bytes, 0 == max available */
public System.UInt32 lo_number;
public System.UInt32 lo_encrypt_type;
public System.UInt32 lo_encrypt_key_size;
public System.UInt32 lo_flags;
// http://stackoverflow.com/questions/1725855/uint8-t-vs-unsigned-char
[System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst = LO_NAME_SIZE)]
public string lo_file_name; // uint8_t lo_file_name[LO_NAME_SIZE];
[System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst = LO_NAME_SIZE)]
public string lo_crypt_name; // uint8_t lo_crypt_name[LO_NAME_SIZE];
[System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValTStr, SizeConst = LO_KEY_SIZE)]
public string lo_encrypt_key; // uint8_t lo_encrypt_key[LO_KEY_SIZE];
[System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.ByValArray, SizeConst = 2)]
public System.UInt64[] lo_init;
}; // End Struct loop_info64
// http://www.student.cs.uwaterloo.ca/~cs350/common/os161-src-html/kern_2include_2kern_2stat_8h.html
protected static bool S_ISBLK(int mode)
{
const uint S_IFMT = 070000;
const uint S_IFBLK = 050000;
return (((mode) & S_IFMT) == S_IFBLK);
} // End Function S_ISBLK
public static int KERNEL_VERSION()
{
Mono.Unix.Native.Utsname unameres = new Mono.Unix.Native.Utsname();
Mono.Unix.Native.Syscall.uname(out unameres);
System.Text.RegularExpressions.Match ma = System.Text.RegularExpressions.Regex.Match(unameres.release, @"(\d+).(\d+).(\d+)(-)?(\d+)?");
string strMajor = ma.Groups[1].Value;
string strMinor = ma.Groups[2].Value;
string strTiny = ma.Groups[3].Value;
string strPatchlevel = ma.Groups[5].Value;
int a = System.Convert.ToInt32(strMajor);
int b = System.Convert.ToInt32(strMinor);
int c = System.Convert.ToInt32(strTiny);
return KERNEL_VERSION(a, b, c);
} // End Function KERNEL_VERSION
//# define KERNEL_VERSION(a,b,c) (((a) << 16) + ((b) << 8) + (c))
public static int KERNEL_VERSION(int a, int b, int c)
{
return (((a) << 16) + ((b) << 8) + (c));
}
public static string CreateVirtualDisk(int iSize)
{
string strBaseDirectory = @"/volumes/";
string strFileName = System.Guid.NewGuid().ToString().Replace("-", "") + ".dsk";
string strFileNameAndPath = System.IO.Path.Combine(strBaseDirectory, strFileName);
using (var fs = new System.IO.FileStream(strFileNameAndPath, System.IO.FileMode.Create, System.IO.FileAccess.Write, System.IO.FileShare.None))
{
fs.SetLength(iSize);
} // End Using fs
return strFileNameAndPath;
} // End Function CreateVirtualDisk
// umount("/mnt/testdisk");
public static bool umount(string strMountPoint)
{
int status = UnsafeNativeMethods.umount(strMountPoint);
if (status == 0)
Console.WriteLine("Successfully unmounted device.");
else
Console.WriteLine("Unmount status: " + status.ToString());
if (status == 0)
return true;
return false;
} // End Function Unmount
public static string find_unused_loop_device()
{
string dev;
int fd;
Mono.Unix.Native.Stat statbuf;
loop_info loopinfo = new loop_info();
loop_info64 lo64 = new loop_info64();
for (int i = 0; i <= 7; i++)
{
dev = "/dev/loop" + i.ToString();
if (System.Convert.ToBoolean(Mono.Unix.Native.Syscall.stat(dev, out statbuf)) == (false && S_ISBLK((int)statbuf.st_mode)))
{
if ((fd = Mono.Unix.Native.Syscall.open(dev, Mono.Unix.Native.OpenFlags.O_RDONLY)) >= 0)
{
// This block was commented out initially
if (UnsafeNativeMethods.ioctl(fd, LOOP_GET_STATUS64, ref lo64) == 0)
{
if (Mono.Unix.Native.Syscall.GetLastError() == Mono.Unix.Native.Errno.ENXIO)
{ // probably free
Mono.Unix.Native.Syscall.close(fd);
return dev;
}
}
if (UnsafeNativeMethods.ioctl(fd, LOOP_GET_STATUS, ref loopinfo) != 0)
{
// http://tomoyo.sourceforge.jp/cgi-bin/lxr/source/include/asm-generic/errno-base.h#L9
// ENXIO - No such device or address
// The device accessed by a command is physically not present,
// or the address of the device is not present
if (Mono.Unix.Native.Syscall.GetLastError() == Mono.Unix.Native.Errno.ENXIO)
{
// that means the device is most-likely free
Mono.Unix.Native.Syscall.close(fd);
return dev;
}
} // End if (UnsafeNativeMethods.ioctl(fd, LOOP_GET_STATUS, ref loopinfo) != 0)
Mono.Unix.Native.Syscall.close(fd);
} // End if ((fd = UnsafeNativeMethods.open(dev, OpenFlags.O_RDONLY)) >= 0)
} // End if (System.Convert.ToBoolean(Mono.Unix.Native.Syscall.stat(dev, out statbuf)) == (false && S_ISBLK((int)statbuf.st_mode)))
} // Next i
return null;
} // End Function find_unused_loop_device
public static int set_loop(string device, string file, int offset, ref int loopro)
{
loop_info loopinfo = new loop_info();
int fd = 0, ffd = 0;
Mono.Unix.Native.OpenFlags mode;
mode = loopro != 0 ? Mono.Unix.Native.OpenFlags.O_RDONLY : Mono.Unix.Native.OpenFlags.O_RDWR;
if (
(
ffd = Mono.Unix.Native.Syscall.open(file, mode)
) < 0
&&
(
(!System.Convert.ToBoolean((int)loopro))
&&
(
Mono.Unix.Native.Syscall.GetLastError() != Mono.Unix.Native.Errno.EROFS
||
(ffd = Mono.Unix.Native.Syscall.open(file, mode = Mono.Unix.Native.OpenFlags.O_RDONLY))
< 0
)
)
) // if
{
Console.WriteLine("Error: file: " + file);
//perror_msg("%s", file);
return 1;
} // End if
if ((fd = Mono.Unix.Native.Syscall.open(device, mode)) < 0)
{
Mono.Unix.Native.Syscall.close(ffd);
Console.WriteLine("Error: device: " + device);
//perror_msg("%s", device);
return 1;
}
loopro = System.Convert.ToInt32(mode == Mono.Unix.Native.OpenFlags.O_RDONLY);
//memset(&loopinfo, 0, sizeof(loopinfo));
//safe_strncpy(loopinfo.lo_name, file, LO_NAME_SIZE);
//strncpy(loopinfo.lo_name, file, LO_NAME_SIZE);
loopinfo.lo_name = string.IsNullOrEmpty(file) ? null : file.Substring(0, Math.Min(file.Length, LO_NAME_SIZE));
loopinfo.lo_offset = offset;
loopinfo.lo_encrypt_key_size = 0;
if (UnsafeNativeMethods.ioctl(fd, LOOP_SET_FD, ffd) < 0)
{
Console.WriteLine("ioctl: LOOP_SET_FD");
//perror_msg("ioctl: LOOP_SET_FD");
Mono.Unix.Native.Syscall.close(fd);
Mono.Unix.Native.Syscall.close(ffd);
return 1;
}
if (UnsafeNativeMethods.ioctl(fd, LOOP_SET_STATUS, ref loopinfo) < 0)
{
int ro = 0;
UnsafeNativeMethods.ioctl(fd, LOOP_CLR_FD, ref ro);
//perror_msg("ioctl: LOOP_SET_STATUS");
Console.WriteLine("ioctl: LOOP_SET_STATUS");
Mono.Unix.Native.Syscall.close(fd);
Mono.Unix.Native.Syscall.close(ffd);
return 1;
}
Mono.Unix.Native.Syscall.close(fd);
Mono.Unix.Native.Syscall.close(ffd);
return 0;
} // End Function set_loop
public static int del_loop(string device)
{
int fd;
if ((fd = Mono.Unix.Native.Syscall.open(device, Mono.Unix.Native.OpenFlags.O_RDONLY)) < 0)
{
//perror_msg("%s", device);
Console.WriteLine("Error description: " + Mono.Unix.Native.Syscall.strerror(Mono.Unix.Native.Syscall.GetLastError()));
return 0;
}
int r = 0;
if (UnsafeNativeMethods.ioctl(fd, LOOP_CLR_FD, ref r) < 0)
{
//perror_msg("ioctl: LOOP_CLR_FD");
Console.WriteLine("ioctl: LOOP_CLR_FD\nError description: " + Mono.Unix.Native.Syscall.strerror(Mono.Unix.Native.Syscall.GetLastError()));
return 0;
}
Mono.Unix.Native.Syscall.close(fd);
Console.WriteLine("Successfully closed loop-device\n");
return 1;
} // End Function del_loop
public static bool mount(string strDevice, string strMountPoint, string strFsType)
{
return mount(strDevice, strMountPoint, strFsType, MountFlags.MS_NOATIME);
}
public static bool mount(string strDevice, string strMountPoint, string strFsType, MountFlags mflags)
{
return mount(strDevice, strMountPoint, strFsType, mflags, IntPtr.Zero);
}
// http://cboard.cprogramming.com/c-programming/126630-using-sys-mount-h-mounting-usb-thumb-drive.html
// http://stackoverflow.com/questions/10458549/mount-usb-drive-in-linux-with-c
// mount("/dev/loop1", "/mnt/testdisk", "vfat");
public static bool mount(string strDevice, string strMountPoint, string strFsType, MountFlags mflags, IntPtr options)
{
// http://linux.die.net/man/2/mount
// MS_RDONLY
// MS_RELATIME (default for Linux >= 2.6.30)
// MS_STRICTATIME (default for Linux < 2.6.30)
if (UnsafeNativeMethods.mount(strDevice, strMountPoint, strFsType, mflags, options) != 0)
{
Mono.Unix.Native.Errno errno = Mono.Unix.Native.Syscall.GetLastError();
if (errno == Mono.Unix.Native.Errno.EBUSY)
{
Console.WriteLine("Mountpoint busy");
}
else
{
Console.WriteLine("Mount error: " + Mono.Unix.Native.Syscall.strerror(errno));
}
return false;
}
else
{
Console.WriteLine("Successfully mounted device !");
}
return true; ;
} // End Function mount
static class UnsafeNativeMethods
{
//string name = "Test";
//TypedReference tf = __makeref(name);
//int c = VarSum(2, __arglist(__makeref(name)));
// http://khason.net/blog/how-to-pinvoke-varargs-variable-arguments-in-c-or-hidden-junk-in-clr/
// //int rv = ioctl(2, 3, __arglist(5, 10));
[System.Runtime.InteropServices.DllImportAttribute("libc", EntryPoint = "ioctl",
CallingConvention = System.Runtime.InteropServices.CallingConvention.Cdecl)]
public static extern int ioctl(int descriptor, int request, __arglist);
[System.Runtime.InteropServices.DllImport("libc", SetLastError = true)]
public static extern int ioctl(int d, int request, int data);
[System.Runtime.InteropServices.DllImport("libc", SetLastError = true)]
public static extern int ioctl(int d, int request, ref int data);
[System.Runtime.InteropServices.DllImport("libc", SetLastError = true)]
public static extern int ioctl(int d, int request, ref loop_info data);
[System.Runtime.InteropServices.DllImport("libc", SetLastError = true)]
public static extern int ioctl(int d, int request, ref loop_info64 data);
//[System.Runtime.InteropServices.DllImport("libc", SetLastError = true)]
//public static extern int open([System.Runtime.InteropServices.MarshalAs(System.Runtime.InteropServices.UnmanagedType.LPStr)]string pathname, OpenFlags flags);
//[System.Runtime.InteropServices.DllImport("libc", SetLastError = true)]
//public static extern int close(int fd);
//[System.Runtime.InteropServices.DllImport("libc", SetLastError = true)]
//public static extern IntPtr read(int fd, IntPtr buffer, UIntPtr count);
///////unsafe public static extern IntPtr read(int fd, void* buffer, UIntPtr count);
// http://linux.die.net/man/2/mount
// http://www.kernel.org/doc/man-pages/online/pages/man2/mount.2.html
[System.Runtime.InteropServices.DllImport("libc", SetLastError = true)]
private static extern int mount(string source, string target, string filesystemtype, UIntPtr mountflags, System.IntPtr data);
//int mount(const char *source, const char *target, const char *filesystemtype, ulong mountflags, const void *data);
public static int mount(string source, string target, string filesystemtype, MountFlags mountflags, System.IntPtr data)
{
System.UIntPtr p = new System.UIntPtr((ulong)mountflags);
return mount(source, target, filesystemtype, p, data);
} // End Function mount
[System.Runtime.InteropServices.DllImport("libc", SetLastError = true)]
public static extern int umount(string strMountPoint);
// extern int umount (__const char *__special_file);
} // End Class UnsafeNativeMethods
public static void TryMount()
{
const bool SUCCESS = true;
// int iReturnCode = Mono.Unix.Native.Syscall.system("mount -a");
// int iReturnCode = Mono.Unix.Native.Syscall.system("mount /volumes/jfs.dsk /mnt/jfs -t jfs -o loop");
// int iReturnCode = Mono.Unix.Native.Syscall.system("mkfs.jfs -O \"jfs.dsk\"");
string strLoopDeviceToUse = find_unused_loop_device();
string strMountPoint = "/mnt/testdisk";
int ro = 0;
set_loop(strLoopDeviceToUse, "/volumes/testdisk.dsk", 0, ref ro);
string strLoopDeviceToUse2 = find_unused_loop_device();
bool status = false;
int mountAttempts = 0;
do
{
//status = mount("/dev/sda1", "/media/usb0", "vfat", MS_MGC_VAL | MS_NOSUID, "");
status = mount(strLoopDeviceToUse, strMountPoint, "vfat", MountFlags.MS_NOATIME);
if (status != SUCCESS)
System.Threading.Thread.Sleep(1000);
mountAttempts++;
} while (status != SUCCESS && mountAttempts < 3);
} // End Sub TryMount
// In gcc or g++, to show all of the macros that are defined for a given platform:
// gcc -dM -E test.c
// or
// g++ -dM -E test.cpp
// http://manual.cream.org/index.cgi/gnu_dev_major.3
// http://www.gnu.org/software/gnulib/coverage/usr/include/sys/sysmacros.h.gcov.frameset.html
// http://en.wikipedia.org/wiki/C_data_types
protected static uint gnu_dev_major(System.UInt64 __dev)
{
return (uint)((uint)(((__dev >> 8) & 0xfff)) | ((uint)(__dev >> 32) & ~0xfff));
}
protected static uint gnu_dev_minor(System.UInt64 __dev)
{
return (uint)((uint)(__dev & 0xff) | ((uint)(__dev >> 12) & ~0xff));
}
public static string loopfile_from_sysfs(string device)
{
string res = null;
Mono.Unix.Native.Stat st;
System.IntPtr f;
//if (stat(device, &st) || !S_ISBLK(st.st_mode))
//if (System.Convert.ToBoolean(Mono.Unix.Native.Syscall.stat(device, out st)) || !S_ISBLK((int) st.st_mode))
// return null;
Mono.Unix.Native.Syscall.stat(device, out st);
const string _PATH_SYS_DEVBLOCK = "/sys/dev/block";
string strPath = string.Format("{0}/{1}:{2}/loop/backing_file", _PATH_SYS_DEVBLOCK, gnu_dev_major(st.st_rdev), gnu_dev_minor(st.st_rdev));
f = Mono.Unix.Native.Syscall.fopen(strPath, "r");
if (f == IntPtr.Zero)
return null;
Mono.Unix.Native.Syscall.fclose(f);
res = System.IO.File.ReadAllText(strPath);
strPath = null;
return res;
} // End Function loopfile_from_sysfs
public static string loopdev_get_loopfile(string device)
{
string res = loopfile_from_sysfs(device);
if (res == null)
{
loop_info lo = new loop_info();
loop_info64 lo64 = new loop_info64();
int fd;
if ((fd = Mono.Unix.Native.Syscall.open(device, Mono.Unix.Native.OpenFlags.O_RDONLY)) < 0)
return null;
if (UnsafeNativeMethods.ioctl(fd, LOOP_GET_STATUS64, ref lo64) == 0)
{
//lo64.lo_file_name[LO_NAME_SIZE-2] = '*';
//lo64.lo_file_name[LO_NAME_SIZE-1] = 0;
//res = strdup((char *) lo64.lo_file_name);
res = lo64.lo_file_name;
Console.WriteLine("LOOP_GET_STATUS64");
}
else if (UnsafeNativeMethods.ioctl(fd, LOOP_GET_STATUS, ref lo) == 0)
{
//lo.lo_name[LO_NAME_SIZE-2] = '*';
//lo.lo_name[LO_NAME_SIZE-1] = 0;
//res = strdup((char *) lo.lo_name);
res = lo.lo_name;
Console.WriteLine("LOOP_GET_STATUS");
}
Mono.Unix.Native.Syscall.close(fd);
} // End if (res == null)
return res;
} // End Function loopdev_get_loopfile
public static void TryUnmount()
{
/*
string strMountPoint = "/mnt/testdisk";
umount(strMountPoint);
System.Threading.Thread.Sleep(1000);
del_loop("/dev/loop2");
*/
string xxx = loopdev_get_loopfile("/dev/loop0");
Console.WriteLine("xxx: " + xxx);
}
// kernel-support:
// grep hfs /proc/filesystems
// cat /proc/partitions
// apt-get install hfsprogs
// sudo modprobe hfsplus
// dd if=/dev/zero of=hfsplus.dsk bs=1048576 count=150
// mkfs.hfsplus /volumes/hfsplus.dsk
// mkfs.hfsplus hfsplus.dsk
// apt-get install jfsutils
// dd if=/dev/zero of=jfs.dsk bs=1048576 count=150
// mkfs.jfs -O jfs.dsk
// mkdir -p /mnt/jfs
// mount /volumes/jfs.dsk /mnt/jfs -t jfs -o loop
// umount /mnt/jfs/
// mkdir -p /mnt/hfsplus
// mount -t hfsplus /volumes/hfsplus.dsk /mnt/hfsplus/ -o loop
//
} // End Class Linux
} // End Namespace Syscalls
// http://ubuntuforums.org/showthread.php?t=135113
// http://stackoverflow.com/questions/7027151/call-expect-script-in-c-process
// http://linux.die.net/man/1/expect
// http://linux.die.net/man/3/libexpect
// http://linuxcommand.org/man_pages/losetup8.html
// losetup /dev/loop0 /file
// losetup -d /dev/loop0
// http://linux.about.com/library/cmd/blcmdl8_losetup.htm
To perma-mount it in fstab, you need to get the partition uuid (blkid)
getmntent can help you read /etc/fstab (and then use the mount function in the other answers).