Living without a RAM disk

For a Linux installation on a hard disk it is quite natural not to use a RAM disk, but for a Linux installation that is booted from a diskette (without depending on a root file system elsewhere) there is only one valid reason not to use a RAM disk: you don't have enough RAM for the RAM disk. As a rule of thumb, if you have less than 6-8MB of RAM. you will probably need to boot without a RAM disk, though it can be achieved with 4MB if you really strip things down.

If you boot from a diskette without a RAM disk, with the root file system on a diskette, the kernel will always prompt for an extra diskette, so the kernel and the root file systems can live on separate diskettes. The root file system cannot be compressed. It is of course possible to put both on a single diskette. In that case the boot diskette contains the root file system and in that root file system the kernel lives, as would be the case with most hard disk installations. On the boot diskette you need to install a boot loader that can live inside that file system, which rules out SYSLINUX, but both GRUB and LILO should do.

Installing Linux on a machine from diskette without a RAM disk is a tricky process, which involves the following steps:

• Boot from a diskette without a RAM disk. The diskette may not be removed from the drive.
• Partition the hard disk, initialize the swap partition with mkswap and create a file system on the hard disk.
• Copy the contents of the root file system from the diskette to the hard disk.
• Reboot and select the root device on the hard disk (that you had just copied). This time the diskette drive is free.
• Copy all your data to the hard disk partition.