Difference between revisions of "Mount"

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(Undo revision 330646 by Andy Crowd (talk) - the previous link provides more up to date manpage)
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* Documentation of file systems supported by kernel: [https://www.kernel.org/doc/Documentation/filesystems/ kernel.org]
 
* Documentation of file systems supported by kernel: [https://www.kernel.org/doc/Documentation/filesystems/ kernel.org]
* Manual for the ''mount'' command: [http://manpages.ubuntu.com/manpages/hardy/man8/mount.8.html manpage]
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* Manual for the ''mount'' command: [http://linux.die.net/man/8/mount linux.die.net]
 
* [[Wikipedia:Mount (Unix)]]
 
* [[Wikipedia:Mount (Unix)]]
 
* Creating and using disk images mini-howto: [http://darkdust.net/writings/diskimagesminihowto darkdust.net]
 
* Creating and using disk images mini-howto: [http://darkdust.net/writings/diskimagesminihowto darkdust.net]

Revision as of 18:49, 16 August 2014

mount is an application used to access file systems, partition tables, and shared folders. It can mount file systems supported by the Linux kernel, but can be extended with other drivers or applications, such as ntfs-3g for mounting NTFS filesystems.

Supported file systems

To view the supported files systems by your kernel and their configurations:

$ zgrep -e 'FS_' -e _FS -e 'CONFIG_ISO' -e  '_NLS=' -e CONFIG_NLS_ISO /proc/config.gz

You can read about supported file systems by the mount command in the manual: man mount.

mtab

The /etc/mtab is a system-generated file created and updated by the mount application whenever any file system is mounted or unmounted.

It lists each device node, mount point and mount options used. Whenever the mount program is executed without any arguments, this file is printed.

Note: The /etc/mtab file is meant to be used to display the status of currently mounted file systems only. It should not be manually modified.

File Definition

Each line in the file represents a file system that is currently mounted and displays the following information:

  • The file system.
  • The mount point.
  • The file system type.
  • Mount options used while mounting the file system.

Alternatives that can be used to change the default options

Here are a few examples about how to extend mount functionality and modify default options. To change the default settings in the kernel you will need to compile the kernel yourself. If the script does not exist then the default options will be used.

The mount.X scripts, where X is the name of a file system, can be used to alter the default mount options for almost any of its supported file systems. Use the -i option to ignore mount.X scripts, mount -i -t reiserfs /dev/sdXY /mnt/sdXY.

VFAT, FAT, DOS

Here is an example of the default mount configuration in the kernel:

$ zgrep -e FAT -e DOS /proc/config.gz | sort -r 
# DOS/FAT/NT Filesystems
CONFIG_FAT_FS=m
CONFIG_MSDOS_PARTITION=y
CONFIG_FAT_FS=m
CONFIG_MSDOS_FS=m
CONFIG_VFAT_FS=m
CONFIG_FAT_DEFAULT_CODEPAGE=437
CONFIG_FAT_DEFAULT_IOCHARSET="iso8859-1"
CONFIG_NCPFS_SMALLDOS=y

A short description of the options:

  • Language settings: CONFIG_FAT_DEFAULT_CODEPAGE, CONFIG_FAT_DEFAULT_IOCHARSET.
  • All filenames to lower letters on a FAT partitions if enabled: CONFIG_NCPFS_SMALLDOS
  • Enables support of the FAT file systems: CONFIG_FAT_FS, CONFIG_MSDOS_FS, CONFIG_VFAT_FS
  • Enables support of a FAT partitioned harddisks on 86x PCs: CONFIG_MSDOS_PARTITION


If the partition type detected by mount is VFAT then it will run the /usr/bin/mount.vfat script.

/usr/bin/mount.vfat
#!/bin/bash
#mount VFAT with full rw (read-write) permissions for all users
#/usr/bin/mount -i -t vfat -oumask=0000,iocharset=utf8 "$@"
#The above is the same as
mount -i -t vfat -oiocharset=utf8,fmask=0000,dmask=0000 "$@"

See also: more details about mounting of the FAT file systems.

NTFS

The default configuration:

$ zgrep ^CONFIG_NTFS  /proc/config.gz
CONFIG_NTFS_FS=m
CONFIG_NTFS_RW=y

The kernel config option CONFIG_NTFS_RW=y enables read-write support for NTFS file systems. It also means the kernel is predefined to use the ntfs-3g driver in read-write mode. The build in support of the NTFS file systems by the kernel is read-only even if read-write is activated by an option.

Note:
  • When ntfs-3g is being installed it might create a symlink /usr/bin/mount.ntfs to the /usr/bin/ntfs-3g.
  • The ntfs-3g mount tool supports many of the same command line options as the linux standard mount utility, but is specialized on mounting of the NTFS formated partitions.
  • By default on mounting the ntfs-3g driver gives the full read-write permissions to the all users. In some situations access with a full permission rights can cause the damage, see NTFS troubleshooting.

The default mount options can be altered when running mount.ntfs by renaming the /usr/bin/mount.ntfs symlink if exists and creating a script in its place with a preferred options or use the -i option (mount -i -t ntfs) to ignore all the mount.X files and use the natively supported functionality by the kernel. This example will mount NTFS as a read-only:

/usr/bin/mount.ntfs
#!/bin/bash
#mount -i -oro "$@"
#mount with a read-only rights
ntfs-3g -oro  "$@" & disown

See man 8 ntfs-3g for more information about the ntfs-3g driver.


You can add more actions for when an external storage device, such as a USB drive or image file (ISO, img, dd), is mounted by using scripts.

See also