Hi, On Tue, Mar 11, 2003 at 08:36:25AM +0000, Miquel van Smoorenburg wrote: > Emile van Bergen <emile-deb@evbergen.xs4all.nl> wrote: > >* add /mem, which is RAM-based, writable /very/ early > > You should use /dev/shm with a shmfs. The location has been standarized, > shmfs shrinks and grows as needed so never takes more memory than > needed, and shmfs data can be put into swap. > > Downside: works only with 2.4.x. kernels. Well, then have /mem be a symlink to /dev/shm/mem on 2.4.x and an older RAM-based FS on older kernels. > > and initialised > > in full from /var/mem at bootup, allowing the admin to define a desired > > initial state; I realised the apparent contradiction, but it's not if you consider this sequence of events: 1. /mem is mounted and empty because it's RAM-based or manually emptied 2. things like ifup can use /mem 3. /var is mounted; contents of /var/mem are copied recursively to /mem, including optionally /var/mem/preserve, without clearing /mem first, so any files that were put in /mem in step 2 that do not exist in /var/mem just stay there 4. things use /mem, optionally /mem/preserve 5. optionally, /mem/preserve is copied back to /var/mem/preserve. > Right ... but /var isn't available at boot. That's kind of the > point of this whole discussion. Debian should define an initial > state and create it (just one or two directories, I guess) > using an init script at early boot. The initial state can be defined as empty before /var is online, or you could choose something like /etc/mem if it's really necessary to have a non-empty state before you have /var that isn't trivial to generate. > But then you could go all the way and have /var/bootstate > as I described. It could be a symlink to /dev/shm/bootstate, > and as soon as the real /var is mounted over it the link > dissapears and the real /var/bootstate appears, at that point > it is easy to copy /dev/shm/bootstate back to it, voila. That only works on kernels that allow you to mount things on non-empty mount points. > This is all trivial to implement. A few lines of scripting. > The hard thing is: what about systems with a 2.2 kernel ? > Or older 2.4 kernels, where shmfs was still a configurable > option (in later 2.4 kernels you can't turn it off) Use any ram-based FS. Cheers, Emile. -- E-Advies - Emile van Bergen emile@e-advies.nl tel. +31 (0)70 3906153 http://www.e-advies.nl
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