Making a RAM Disk Larger than 8 Megabytes
You can set a boot parameter to have Minix create a RAM disk larger
than 8 Mbytes, and if you don't copy the root file system to the RAM
disk you can then use mkfs to make a file system that uses all the RAM
you have reserved. But if you try to copy from a standard floppy disk
to a large RAM disk, you will find that only 8 Mbytes will actually be
used. The reason is that the file system you copy from the floppy disk
has only one block, 1024 bytes or 8192 bits, for its zone bitmap. The
solution to the 8MB RAM disk limit is to enlarge the zone bitmap on the
floppy disk by supplying an appropriate option to the mkfs program.
Here is Kees Bot's explanation of how to do it:
If you want to create a file system on a floppy that has many bitmap
blocks then this should work:
mkfs -t /dev/fd0 65535
de -w /dev/fd0
(Type PageDown, arrow down to reach the V1 or V2 "number of
zones" field with 65535 in it. Type 's' 1440 ENTER.)
Now you have a floppy file system that FS can expand up to 65536 blocks.
(I used 65535 instead of 65536 to make it easier to find and change. With
65536 you'll see 0 and 1 at the V2 field.)
If you use a script to fill a floppy then change the mkfs as above, and
run 'de' later. Maybe you can even forget about 'de', I don't think FS
minds if it hits the end of the image device early. It's just not right
How many i-nodes?
When a file system is created using mkfs a number of i-nodes
proportional to the size of the medium are created if you don't
explicitly specify a number with the -i option.
These are the default mkfs actions:
size i-nodes blocks
free used fd-free
----- ------- ------ ------ --------
720K 240 700 20
1024K 352 997 27
1200K 400 1170 30
1440K 480 1405 35 1405
2048K 688 2000 48 1392
4096K 1376 4005 91 1349
8192K 2736 8016 176 1264
16384K 5472 16036 348 1092
32768K 8192 32427 521 919
65536K 10928 64840 696 744
The last column above is the number of free blocks you will have if you
create the file system data structures on a floppy disk.
How many i-nodes do you need?
Here are actual i-node usages of a few systems:
pre-install 2.0.3 system (root.mnx + usr.mnx): 229
a complete installed Minix 2.0.3 dosminix 3170
minix1.hampshire (2.0.2, 1.9G disk) total: 10747
" / + /usr + /usr/local only: 6968
How much floppy space do you need?
A Minix 2.0.4 install disk uses 359 (of 480) + 694 (of 720)
blocks on /dev/fd0p0 and /dev/fd0p2, for a total of 1053
blocks. So we can easily make an install disk that initializes
a 16M RAM disk with 5472 i-nodes.