Hi HPA and Joao,
support for EXT3 in the kernel would indeed be large/complex.
Only supporting EXT3 READS already would take circa 10 kB of
code, taking the size of the EXT2/3/4 GRUB module as example.
I like MEMDISK bootable ramdisk style: MEMDISK can be booted
by boot loaders which are able to boot Linux, and it can use
any diskimage accessible by such boot loaders, including an
image on EXT3 disks. Boot loaders either pre-compute a list
of sectors to read files or load extra driver modules, which
only have to support reading and which are not kept in RAM.
Regarding the idea to have the kernel "natively boot from a
RAMDISK in HIGH MEMORY which would NOT be A: or C: ... Well,
on modern computers it should not be a problem to "hog" the
drive letter of the A: floppy drive - you probably have at
most ONE real floppy next to that ramdisk anyway and letter
B: is still free :-) So in that sense, MEMDISK is ok for me.
A ramdisk is often very small in RAM, so I think the benefit
of compiling one into the kernel would be small compared to
simply using pre-existing 3rd party ramdisks like MEMDISK.
However, for the fans of really tiny settings, have a look at:
This project features a "bios" version of the FreeDOS kernel,
by booting the kernel from a 63 kB virtual floppy. The module
including the floppy takes 64 kB in the option ROM area, so
you could compare it to booting FreeDOS from UMB ramdisk ;-)
In totally unrelated notes, I think it would be cool if the
FreeDOS kernel could parse GPT PARTITION TABLES and find FAT
partitions in them. And I think it might be interesting to
be able to read files from the root dir of ISO9660 media if
I/O is provided by BIOS ElTorito calls: That way, the kernel
could load config sys and a CD/DVD driver after some special
boot sector has loaded the kernel directly from CD/DVD :-)
PS: I admit that the last idea is similar to having read-only
EXT3 support in the kernel, but I believe ISO takes << 10 kB.
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