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serenity/Base/usr/share/man/man2/mount.md

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Name

mount - mount a filesystem

Synopsis

#include <unistd.h>

int mount(int source_fd, const char* target, const char* fs_type, int flags);

Description

mount() mounts a filesystem stored at source_fd by overlaying its contents over target.

fs_type must be one of the following supported filesystems:

  • Ext2FS (or ext2): The ext2 filesystem.
  • ProcFS (or proc): The process pseudo-filesystem (normally mounted at /proc).
  • DevPtsFS (or devpts): The pseudoterminal pseudo-filesystem (normally mounted at /dev/pts).
  • TmpFS (or tmp): A non-persistent filesystem that stores all its data in RAM. An instance of this filesystem is normally mounted at /tmp.

For Ext2FS, source_fd must refer to an open file descriptor to a file containing the filesystem image. This may be a device file or any other seekable file. All the other filesystems ignore the source_fd — you can even pass an invalid file descriptor such as -1.

The following flags are supported:

  • MS_NODEV: Disallow opening any devices from this file system.
  • MS_NOEXEC: Disallow executing any executables from this file system.
  • MS_NOSUID: Ignore set-user-id bits on executables from this file system.
  • MS_BIND: Perform a bind-mount (see below).

These flags can be used as a security measure to limit the possible abuses of the newly mounted file system.

Bind mounts

If MS_BIND is specified in flags, fs_type is ignored and a bind mount is performed instead. In this case, the file or directory specified by source_fd is overlayed over target — the target appears to be replaced by a copy of the source. This can be used as an alternative to symlinks or hardlinks.

Errors

  • EFAULT: The fs_type or target are invalid strings.
  • EPERM: The current process does not have superuser privileges.
  • ENODEV: The fs_type is unrecognized, or the file descriptor to source is not found, or the source doesn't contain a valid filesystem image. Also, this error occurs if fs_type is valid, but the file descriptor from source_fd is not seekable.
  • EBADF: If the source_fd is not valid, and either fs_type specifies a file-backed filesystem (and not a pseudo filesystem), or MS_BIND is specified in flags.

All of the usual path resolution errors may also occur.

See also