If the source medium is partitioned, one partition must be selected to be mounted. If there is only one HFS partition on the medium, it will be selected by default. Otherwise, the desired partition number must be specified (as the ordinal nth HFS partition) on the command-line. Partition number 0 can be specified to refer to the entire medium, ignoring what might otherwise be perceived as a partition map, although in practice this is probably only useful if you want this command to fail when the medium is partitioned.

The mounted volume becomes "current" so subsequent commands will refer to it. The current working directory for the volume is set to the root of the volume. This information is kept in a file named .hcwd in the user's home directory.

If the source medium is changed (e.g. floppy or CD-ROM disc exchanged) after hmount has been called, subsequent HFS commands will fail until the original medium is replaced or a different volume is made current. To use the same source path with the different medium, reissue the hmount command.

% hmount /dev/fd0

If a Macintosh floppy disk is available as /dev/fd0, this command makes the floppy current for other HFS commands such as hls(1), hcd(1), hcopy(1), etc.

% hmount /dev/sd2 1

If a SCSI disk is available as /dev/sd2, this command finds the first HFS partition on the medium and makes it available for other HFS operations.