|MOUNT(2)||Linux Programmer's Manual||MOUNT(2)|
NAMEmount - mount file system
int mount(const char * source , const char * target ,
const char * filesystemtype , unsigned long mountflags ,
const void * data );
DESCRIPTIONmount() attaches the file system specified by source (which is often a device name, but can also be a directory name or a dummy) to the directory specified by target.
- MS_BIND (Linux 2.4 onward)
- Perform a bind mount, making a file or a directory subtree visible at another point within a file system. Bind mounts may cross file system boundaries and span chroot(2) jails. The filesystemtype and data arguments are ignored. Up until Linux 2.6.26, mountflags was also ignored (the bind mount has the same mount options as the underlying mount point).
- MS_DIRSYNC (since Linux 2.5.19)
- Make directory changes on this file system synchronous. (This property can be obtained for individual directories or subtrees using chattr(1).)
- Permit mandatory locking on files in this file system. (Mandatory locking must still be enabled on a per-file basis, as described in fcntl(2).)
- Move a subtree. source specifies an existing mount point and target specifies the new location. The move is atomic: at no point is the subtree unmounted. The filesystemtype, mountflags, and data arguments are ignored.
- Do not update access times for (all types of) files on this file system.
- Do not allow access to devices (special files) on this file system.
- Do not update access times for directories on this file system. This flag provides a subset of the functionality provided by MS_NOATIME; that is, MS_NOATIME implies MS_NODIRATIME.
- Do not allow programs to be executed from this file system.
- Do not honor set-user-ID and set-group-ID bits when executing programs from this file system.
- Mount file system read-only.
- MS_RELATIME (Since Linux 2.6.20)
- When a file on this file system is accessed, update the file's last access time (atime) only if the current value of atime is less than or equal to the file's last modification time (mtime) or last status change time (ctime). This option is useful for programs, such as mutt(1), that need to know when a file has been read since it was last modified. Since Linux 2.6.30, the kernel defaults to the behavior provided by this flag (unless MS_NOATIME was specified), and the MS_STRICTATIME flag is required to obtain traditional semantics. In addition, since Linux 2.6.30, the file's last access time is always updated if it is more than 1 day old.
Remount an existing mount. This allows you to change the
data of an existing mount without having to unmount and remount the file system.
target should be the same value specified in the initial
filesystemtype are ignored.
- MS_SILENT (since Linux 2.6.17)
- Suppress the display of certain ( printk()) warning messages in the kernel log. This flag supersedes the misnamed and obsolete MS_VERBOSE flag (available since Linux 2.4.12), which has the same meaning.
- MS_STRICTATIME (Since Linux 2.6.30)
- Always update the last access time (atime) when files on this file system are accessed. (This was the default behavior before Linux 2.6.30.) Specifying this flag overrides the effect of setting the MS_NOATIME and MS_RELATIME flags.
- Make writes on this file system synchronous (as though the O_SYNC flag to open(2) was specified for all file opens to this file system).
From Linux 2.4 onward, the MS_NODEV, MS_NOEXEC, and MS_NOSUID flags are settable on a per-mount-point basis. From kernel 2.6.16 onward, MS_NOATIME and MS_NODIRATIME are also settable on a per-mount-point basis. The MS_RELATIME flag is also settable on a per-mount-point basis.
The data argument is interpreted by the different file systems. Typically it is a string of comma-separated options understood by this file system. See mount(8) for details of the options available for each filesystem type.
RETURN VALUEOn success, zero is returned. On error, -1 is returned, and errno is set appropriately.
ERRORSThe error values given below result from filesystem type independent errors. Each file-system type may have its own special errors and its own special behavior. See the Linux kernel source code for details.
- A component of a path was not searchable. (See also path_resolution(7).) Or, mounting a read-only file system was attempted without giving the MS_RDONLY flag. Or, the block device source is located on a file system mounted with the MS_NODEV option.
- source is already mounted. Or, it cannot be remounted read-only, because it still holds files open for writing. Or, it cannot be mounted on target because target is still busy (it is the working directory of some thread, the mount point of another device, has open files, etc.).
- One of the pointer arguments points outside the user address space.
- source had an invalid superblock. Or, a remount ( MS_REMOUNT) was attempted, but source was not already mounted on target. Or, a move ( MS_MOVE) was attempted, but source was not a mount point, or was '/'.
- Too many links encountered during pathname resolution. Or, a move was attempted, while target is a descendant of source.
- (In case no block device is required:) Table of dummy devices is full.
- A pathname was longer than MAXPATHLEN.
- filesystemtype not configured in the kernel.
- A pathname was empty or had a nonexistent component.
- The kernel could not allocate a free page to copy filenames or data into.
- source is not a block device (and a device was required).
- target, or a prefix of source, is not a directory.
- The major number of the block device source is out of range.
- The caller does not have the required privileges.
VERSIONSThe definitions of MS_DIRSYNC, MS_MOVE, MS_REC, MS_RELATIME, and MS_STRICTATIME were added to glibc headers in version 2.12.
CONFORMING TOThis function is Linux-specific and should not be used in programs intended to be portable.
NOTESThe original MS_SYNC flag was renamed MS_SYNCHRONOUS in 1.1.69 when a different MS_SYNC was added to <mman.h>.
Before Linux 2.4 an attempt to execute a set-user-ID or set-group-ID program on a file system mounted with MS_NOSUID would fail with EPERM. Since Linux 2.4 the set-user-ID and set-group-ID bits are just silently ignored in this case.
Per-process namespacesStarting with kernel 2.4.19, Linux provides per-process mount namespaces. A mount namespace is the set of file system mounts that are visible to a process. Mount-point namespaces can be (and usually are) shared between multiple processes, and changes to the namespace (i.e., mounts and unmounts) by one process are visible to all other processes sharing the same namespace. (The pre-2.4.19 Linux situation can be considered as one in which a single namespace was shared by every process on the system.)
SEE ALSOumount(2), namespaces(7), path_resolution(7), mount(8), umount(8)
COLOPHONThis page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.