man cramfs
man ramdisk
man rootflags
man ext
if you are trying to make a ROM of 5 MB to boot off some handheld device as a bootrom or something like that?
http://embedded.centurysoftware.com/docs/nx/index.html
take a peek here. peck-a-booooooooo!
http://embedded.centurysoftware.com/...e-ramdisk.html
bullz-eye!
plus, are you using busybox? and ext2,ext3 for ramfs or romfs then dont use ext2/3 they use journalling flag option. try jffs or readonly filesystems like LZMA where you dont have +w option i.e. its simple +r else i am not sure unless i get the right info.