i'm trying to figure out what i can and can't do with ram disks, so let me explain what i've found so far, and perhaps someone can fill in the gaps.
by "ram disk", i don't mean the boot-time initrd image. i mean setting aside an arbitrary amount of RAM, formatting it as an ext2/3 filesystem, mounting it, filling it with files, and then having smokin' fast access to those files. (as an aside, i wanted to test this by creating a ram disk big enough for the kernel source directory, to see just how much faster a kernel build would run.) so, under RH 9 and with the 2.5.72 kernel, i can see the kernel option for "RAM disk support", and a default size of 4096 (kilobytes, or 4M). from what i've read, i can create a number of ram disks corresponding to /dev/ram[012345...], by doing the following: # dd if=/dev/zero of=/dev/ram0 bs=1024 count=16 for a tiny ram disk of 16k (supposedly). so what actually happens? if i try to create an ext2 filesystem on it: # mke2fs /dev/ram0 it works, but it's obvious that it's 4M in size -- the default. i didn't *ask* for the default size, i was hoping i could pick the size myself. but i get 4M anyway. (i can mount that filesystem, and "df" shows the same thing: 4M). the same thing happens no matter what size i use for "dd", until i try to go over 4M, at which point, at the 4097th write (just past 4M), i get "No space left on device". in short, no matter what i ask for, i'll get a 4M ram disk. so, the questions: 1) is there any way to create a ram disk of an arbitrary size, regardless of the kernel config value for default size? 2) once i create a ram disk, is there an indicator that tells me that such a thing exists? i mean, "free" will show me that there's less free space, but that's about it. is there maybe an entry under /proc keeping track of ram disks? you know ... maybe /proc/list_of_ram_disks?? :-) 3) once i create one (even if i'm still stuck with 4M), how can i manually release it? and again, is there a way to verify the return of that ram disk space to the OS? rday -- Robert P. J. Day Eno River Technologies Unix, Linux and Open Source training Waterloo, Ontario www.enoriver.com -- redhat-list mailing list unsubscribe mailto:[EMAIL PROTECTED] https://www.redhat.com/mailman/listinfo/redhat-list
