Section 4 gave instructions for building a compressed root
filesystem which is loaded to ramdisk when the system boots. This method
has many advantages so it is commonly used. However, some systems with
little memory cannot afford the RAM needed for this, and they must use root
filesystems mounted directly from the diskette. Such filesystems are actually easier to build than compressed root filesystems
because they can be built on a diskette rather than on some other device, and
they do not have to be compressed. We will outline the procedure as it
differs from the instructions above. If you choose to do this, keep in mind
that you will have much less space available.
Calculate how much space you will have available for root files.
If you are building a single boot/root disk, you must fit all blocks for the
kernel plus all blocks for the root filesystem on the one disk.
Using mke2fs, create a root filesystem on a diskette of the
appropriate size.
Populate the filesystem as described above.
When done, unmount the filesystem and transfer it to a disk file
but do not compress it.
Transfer the kernel to a floppy diskette, as described above. When
calculating the ramdisk word, set bit 14 to zero, to indicate that the
root filesystem is not to be loaded to ramdisk. Run the rdev's as
described.
Transfer the root filesystem as before.
There are several shortcuts you can take. If you are building a
two-disk set, you can build the complete root filesystem directly on the
second disk and you need not transfer it to a hard disk file and then back.
Also, if you are building a single boot/root disk and using LILO, you can
build a single filesystem on the entire disk,
containing the kernel, LILO files and root files, and simply run LILO as
the last step. Building a utility disk is relatively easy -- simply create a filesystem
on a formatted disk and copy files to it. To use it with a bootdisk,
mount it manually after the system is booted. In the instructions above, we mentioned that the utility disk could be
mounted as /usr. In this case, binaries could be placed into a
/bin directory on your utility disk, so that placing
/usr/bin in your path will access them. Additional libraries
needed by the binaries are placed in /lib on the utility disk. There are several important points to keep in mind when designing a utility
disk:
Do not place critical system binaries or libraries onto the utility
disk, since it will not be mountable until after the system has booted.
You cannot access a floppy diskette and a floppy tape drive
simultaneously. This means that if you have a floppy tape drive, you will not
be able to access it while your utility disk is mounted.
Access to files on the utility disk will be slow.
Appendix D shows a sample of files on a utility disk.
Here are some ideas for files you may find useful: programs for examining
and manipulating disks (format, fdisk) and filesystems
(mke2fs, fsck, debugfs, isofs.o), a lightweight text
editor (elvis, jove), compression and archive utilities
(gzip, bzip, tar, cpio, afio), tape utilities
(mt, ftmt, tob, taper), communications utilities
(ppp.o, slip.o, minicom) and utilities for devices
(setserial, mknod). |
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