>
> Hopefully, someone more expert can tell us both exactly what the new-style
> way of setting aside a RAMdisk is...? And how it to address it to read and
> write to it.
RAMDISKS are not set aside statically, that would be quite a waste, the RAMDISK
resides in buffer cache, the size you pass to the kernel ither during compilation or
on the "commandline" is the maximum size the ramdisk can reach , but if you set up a
filesystem on a ramdisk and don't populate it with files then it will only use a few
bytes required for the super-block of the fs used .
durinc kernel compilation the ramdisk size can be set
->Block Devices
-> RAM disk support
-> Default RAM disk size (4096)
that is if you now boot the kernel and do a simple
mkfs.ext2 /dev/ram0
mkfs.ext2 /dev/ram1
mount -t ext2 /dev/ram0 /ramdisk1
mount -t ext2 /dev/ram1 /ramdisk2
then this filesystem will be 4096K minus the ext2 super-block (about 130K)
and the lost+found (13K) but it will only take about 145K of physical memmory
(allocated in buffer cache)
Filesystem 1k-blocks Used Available Use% Mounted on
/dev/hda5 9770224 1771080 7502832 19% /
/dev/hda1 21929 10502 10295 50% /boot
/dev/ram0 3963 13 3746 0% /ramdisk1
/dev/ram1 3963 13 3746 0% /ramdisk2
(assuming a default RAMDISK size set in the kernel of 4096K)
to change the default size of the RAMDISK at system boot ither pass it as a
commandline parameter at the boot prompt as "ramdisk_size=8192" or put it in
/etc/lilo.conf as
append="ramdisk_size=8192"
(you are not required to use 2^n but its resonalbe since memory is organized
in 2^n blocks)
if you initialize a filesystem on /dev/ram0 then you can't directly write to
it, that is if you treat it as a raw-block device you will corupt any fs on
it. If you want to use it as a raw block-device, and directly write to
/dev/ram0 then you naturally don't set up a filesystem on it, but I see
littl sense in using a RAMDISK for that, its probably simpler to use
the shared memory API for that (-> mbuff)
hofrat
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