Project66.Manage File Systems

Project 66. Manage File Systems

"How do I find out what local disks and remote volumes are mounted?"

This project explains what a file system is and then shows you how to list and obtain information about currently mounted file systems. It covers the commands lsvfs, df, and du. Projects 67 and 68 show what you can do with Apple's diskutil command.

Systems and Sharing

We think of a disk in terms of the files and directories it contains and perhaps other properties, such as owners, permissions, and file metadata. The way this information is represented on the disk is a consequence of the system software that creates, reads, and writes files on the disk. This software defines the type of file system employed on the disk. The native file system in Mac OS X is Apple's HFS+ (Hierarchical File System); in other Unix systems, it's UFS (Unix File System).

File systems are not limited to local drives. If we mount a share from another Mac by using AppleShare, another file system is needed to manage the remote volume in accordance with the protocol by which the local and remote machines communicate. In the case of AppleShare, the file system and the protocol are called AFP (Apple File Protocol).

List File Systems

Use the lsvfs command to list all file systems currently loaded (but not necessarily in use). For example:

$ lsvfs Filesystem                 Refs Flags ------------------------- ----- --------------- ufs                           0 local nfs                           5 fdesc                         1 cd9660                        0 local union                         0 hfs                           3 local, dovolfs volfs                         1 devfs                         1 afpfs                         2 webdav                        1 udf                           1 local

The Refs column refers to the number of currently mounted volumes (disks, partitions, and shares) of that file-system type. When a file system is flagged as local, it means that the device is attached to the local machine and not a remotely mounted share from another machine.

Reading the output from lsvfs, we see that the local file systems comprise no UFS volumes, no CD-ROMs (file system cd9660), tHRee HFS+ volumes, and one DVD (file system udf). We also see three remote shares: two AppleShare (afpfs) mounts and a WebDAV mount. WebDAV is the protocol used by dot-Mac to mount your iDisk. The supposed five NFS (Network File System) shares reflect (I think) four NFS IO daemons launched at system startup and an FTP (File Transfer Protocol) server mounted by the Finder.

Note: The remainder (fdesc, union, volfs, and devfs) are special file systems that map device names to the device drivers in /dev and also manage the mysterious /.vol directory.

Discover Mounted Drives

The lsvfs command shows the active file systems and how many mounted volumes each of them services. Use df to discover what is actually mounted, displaying the device and its path, or mount point. The df command also displays the size and available capacity of each mounted volume. (Option -h displays the capacity data in human-readable form, with size-unit abbreviations; omit the flag to see how nonhumans read the data.)

$ df -h Filesystem                Size ... Mounted on /dev/disk0s3              234G ... / devfs                     100K ... /dev fdesc                     1.0K ... /dev <volfs>                   512K ... /.vol automount -nsl [188]        0B ... /Network automount -fstab [192]      0B ... /automount/Servers automount -static [192]     0B ... /automount/static /dev/disk1s3               20G ... /Volumes/Macintosh HD /dev/disk1s5              129G ... /Volumes/Backup-sauron afp_0TQCUU0QrZsg00vJDV...  12G ... /Volumes/saruman afp_0TQCUU0QrZsg00vJDV...  12G ... /Volumes/OSX-saruman /dev/disk2                4.9G ... /Volumes/MONTY_PYTHON https://secure/webdav/ -512.0B ... /Volumes/share ftp://carcharoth          1.0G ... /Volumes/carcharoth

Learn More

Projects 67 and 68 use the diskutil command to manage local drives and to manually mount and unmount them.

The Mounted on column shows the Unix pathname of the mounted volume. The automount volumes control remote volumes that you'll observe below the Network icon in the top-left pane of the Mac OS X Finder.

Mount Points

In Unix, a volume (disk, partition, or remote mount) does not have a name by which you reference it. This is at odds with the Mac OS X Finder, which gives all volumes names. In the Finder, mounted volumes such as CD-ROMs, external drives, and file servers are represented on a peer level with the system disk. In Unix, nothing is on a peer level with the system disk; all other volumes are mounted within it, and their pathnames are listed under its root.

When a disk is mounted, it mounts into a directory. This can be any directory anywhere on the file system but generally is one created specifically for the mount and named appropriately. Darwin automatically mounts all volumes at /Volumes/name-of-vol-in-Finder. A mounted volume named Backup-sauron, then, appears to the Unix command line as /Volumes/Backup-sauron.

You may use Apple's diskutil command to list mounted volumes, but it shows only local disk drives.

$ diskutil list /dev/disk0   #:                   type name          size   identifier   0: Apple_partition_scheme              *233.8 GB disk0   1:    Apple_partition_map                31.5 KB disk0s1   2:              Apple_HFS OSX-sauron    233.6 GB disk0s3 /dev/disk1   #:                   type name          size   identifier   0: Apple_partition_scheme              *149.1 GB disk1   1:    Apple_partition_map                31.5 KB disk1s1   2:              Apple_HFS Macintosh HD   19.8 GB disk1s3   3:              Apple_HFS Backup-sauron 129.0 GB disk1s5

Tip

To view information on just local drives, type

$ df -lh

Tip

To total the size of all files in a particular directory hierarchy, use the du command. To find the total size of all files in your home directory, for example, type

$ du -hs ~

To get a breakdown by directory, type

$ du -hs ~/*