mount <directory> <storage-device-name> <file-system-type>

Attaches a file system on a storage device to the visible set of directories and files you can see and work with.

Think of mounting a file system like plugging in something to a power outlet. Once you have plugged it in and turned it on, it is available to use. This is basically how file systems work.

The first parameter is the directory, this can be any existing empty directory in the file system. For example /harddisk, /ramdisk, etc.
The second parameter is a storage device name. Storage device names are allocated by the system. Hard disks (SATA, NVMe etc) start with hd and are suffixed by number starting at 0, so the first found hard disk is hd0, the next hd1 etc. Ram disks start with ram amd a number. CD/DVD drives start with cd and a number.
The third parameter is a file system type, supported file system types are listed below.

File system type	Full name	Description
rfs	RetroFS, the Retro Rocket native file system	Readable, writeable file system for large hard disks, e.g. NVMe, SATA. The default file system type for fixed disks and ramdisks
iso9660	ISO 9660 file system for CDs and DVDs	Read-only file system mainly for CDs and DVDs. The default file system of the Retro Rocket LiveCD
adfs	Acorn ADFS "L" Format	Read-only file system for Acorn BBC Micro Floppy disks - The Advanced Disk Filing System
dfs	Acorn DFS DS/DD 80T Format	Read-only file system for Acorn BBC Micro Floppy disks - The Disk Filing System
fat32	FAT32 DOS and Windows file system	Readable, writeable file system used for removable media, and the recovery/boot partition of installed systems
ext2	Linux Extended File system (ext2, ext3)	Read-only file system used on Linux systems. Can be read from to move data into Retro Rocket. Will not mount volumes needing recovery
udf	UDF (Universal Disk Format)	Read-only file system used for removable media such as CD/DVD/Blu-Ray. Often seen on rewritable or multi-session media.
devfs	Device tree file system	Readable, writeable file system which device drivers may use to expose device-specific information and control surfaces. *
dummyfs	Dummy File System	The dummy file system does nothing, you cannot read or write to it. It is the placeholder for everything until the system boots

For devfs, you cannot create arbitrary files in this file system. Your ability to read from, or write to the files in this directory depends on the behaviour of the driver which places the file there.

Example

mount /harddisk hd0 rfs

Notes

Mounting a storage device with a file system it is not configured for will result in an error
Unmounting file systems is not yet supported. To clear a mounting, it is currently required that you reboot the system.