Mount
The Mediawiki system (the 'software' that runs this site) capitalises all articles. Please note that commands on most UNIX and Unix-like systems are entered in lower case. As an example the article documenting the Ln command would be issued from the command line as 'ln'.
The mount command is used to link a file system to the local host allowing access to files stored upon them. These file systems could be on physical media, such as a hard drive, CD-ROM or USB memory key, or virtual media, such as file server shares. FreeBSD has support for reading from a large number of file systems and can write back to a majority of them.
Contents |
Operation
The mounting of a file system to the local host works by creating a mount-point at which the file system can be accessed. This fits in with the Unix concept of 'everything is a file' and as such a CD-ROM drive, for example, is typically mounted as '/cdrom'. Other file systems are typically mounted under the '/mnt' directory. The technical term is called 'grafting' a device to the local file system tree.
An typical installation of FreeBSD might have the following mount-points:
/ - file system root; /var - log files; /usr - user specific directories, ports, etc.; /tmp - temporary workspace; /cdrom - physical CD-ROM drive.
These mount-points are automatically mounted when the system is started because they are stored in a file called '/etc/fstab' (derived from File System TABle). The fstab file used to mount the above listed mount-points contains the following entires:
# Device Mountpoint FStype Options Dump Pass# /dev/ad0s1b none swap sw 0 0 /dev/ad0s1a / ufs rw 1 1 /dev/ad0s1e /tmp ufs rw 2 2 /dev/ad0s1f /usr ufs rw 2 2 /dev/ad0s1d /var ufs rw 2 2 /dev/acd0 /cdrom cd9660 ro,noauto 0 0
The mounted file systems in this example are physical devices attached to the local system and located under the /dev directory with the hard drive being 'ad0s1x' and CD-ROM being 'acd0'. The 'none' mount-point simply exists to inform the system of where the swap-file (often called 'virtual memory') is located. Further details of the fstab file can be found in the fstab article.
Mount Commands
The mount command on its own mounts FreeBSD formatted (or UFS or UFS2) file systems. In order to mount foreign (or non-native FreeBSD formatted) file systems each supported file system has its own mount command in the format of 'mount_filesystem'; as an example the supported 'MS-DOS' (or DR-DOS, FAT16 or FAT32) formatted file system has the command 'mount_msdosfs'.
The following file systems are supported by FreeBSD:
CD-ROM
The mount_cd9660 command mounts file systems formatted using ISO 9660. This is limited to optical media conforming to CD-ROM standards and can include writable CD-R and re-writable CD-RW medium - though this is limited to read-only. Applications within the ports system are available to create (or write) to CD-R and CD-RW media.
Example:
# mount_cd9660 /dev/acd0 /cdrom # ls /cdrom/ .cshrc INSTALL.HTM boot.catalog media sys .profile INSTALL.TXT cdrom.inf mnt tmp 6.3-RELEASE README.HTM dev packages tools COPYRIGHT README.TXT docbook.css proc usr ERRATA.HTM RELNOTES.HTM etc rescue var ERRATA.TXT RELNOTES.TXT floppies root HARDWARE.HTM bin lib sbin HARDWARE.TXT boot libexec stand
devfs
mount_devfs
DVD
The mount_udf command mounts file systems formatted using Universal Disk Format. This is limited to optical media conforming to DVD-ROM standards and can include writable DVD-R, DVD+R and re-writable DVD-RW, DVD+RW and DVD-RAM medium - though this is limited to read-only and to data DVDs. Applications within the ports system are available to create (or write) to the various DVD media. Video DVDs are typically encrypted to stop piracy and as such may not mount successfully.
File Descriptor
mount_fdescfs
Linux ext2
mount_ext2fs
Linux Process
mount_linprocfs
Linux System
mount_linsysfs
MFS
mount_mfs
Microsoft DOS (FAT16 or FAT32)
The mount_msdosfs command mounts file systems formatted using File Allocation Table. This is typically the format used in older versions of Microsoft Windows as well as common memory cards and USB memory keys. FreeBSD supports reading and writing to this file system.
Example (using a USB memory key):
# mkdir /mnt/usb # mount_msdosfs /dev/da0s1 /mnt/usb # ls /mnt/usb/ BackupA1 Drivers BackupA2 Listing BackupA3 Support #
The above example creates the initial mount-point for the USB memory key using the mkdir command. This needs to be done only once.
Microsoft NT (NTFS)
The mount_ntfs command mounts file systems formatted using Microsoft's proprietary New Technology File System. This is typically the format used in newer versions of Microsoft Windows. FreeBSD supports reading from this file system. There are projects actively working towards supporting the writing to this file system in various stages of progress however it is strongly recommended that read-only access to NTFS file systems is used on essential data drives.
Null
mount_nullfs
Process
mount_procfs
Reiser
The mount_reiserfs command mounts file systems formatted using Reiser (but not the newer Resier version 4). This is privately developed file system created by [[http://en.wikipedia.org/wiki/Hans_Reiser Hans Reiser] and his Namesys company though the file system is available for free on open source operating systems. FreeBSD supports reading from this file system.
Standard
mount_std
UMAP
mount_umapfs
Union
mount_unionfs
mount_nfs
mount_nfs4
