An installable file system is a file system in which software is installed when the operating system is started. The OS/2 operating system supports installable file systems and permits users to have multiple file systems active at the same time.

Users install a file system by specifying the file system components in the CONFIG.SYS file. The file system software consists of device drivers and dynamic link libraries. The device drivers access storage devices; the dynamic link libraries control the format of information on a device and manage the flow of data to and from the device. The user must use the DEVICE= command to specify the device driver and the IFS= command to specify the dynamic link library.

Installable file system drivers are loaded during system initialization when an IFS= statement is encountered in the CONFIG.SYS file. The operating system loads the device driver and dynamic link library and initializes a specific device for use with a file system.

These file systems can support file and directory structures different from the FAT file system.

An example of an installable file system might be a file system designed specifically for use on a network server. Another example of an installable file system is the High Performance File System (HPFS), which is included with the OS/2 operating system.