New Feature? Configuration for ramdisks/hdd...

[Dean Brown]

Ralph Stickley wrote:
> 
> Adi,
> We are in the process of switching to the new-improved-latest version
> of PeeWee linux.  One problem occured which I may have a solution for
> (or you may have a better solution) is trying to build our own unique
> filesystem - one that doesn't match the one built by pwl_target*
> scripts...
> 
> If you recall, our system contains the following partitions:
> 1. boot/root partition (ro)
> 2. user partition (rw)
> 3. Ramdisk for /etc
> 4. Ramdisk for /dev
> 
> So, using the new target hardware we select the "read only root"
> with multiple ramdisks..
> 
> However, the pwl_target* scripts force us to use the /home directory
> as a ramdisk, mirrored from another partition.  While this may be a
> good choice, it seems that the configuration tool should not dictate
> the file system (since everything else is configurable).
> 
> Anyhow, I have have been hacking on pwl_target* scripts (without GUI
> support yet) for the following:
> ...in some init function for now (will be default parameters)...
>    hd_mnt_0=/
>    hd_mnt_1=
>    ...
>    hd_mnt_7=
>    rd_mnt_0=
>    rd_mnt_1=/dev
>    rd_mnt_2=/etc
>    rd_mnt_3=/tmp
>    ...
>    rd_mnt_7=
> 
> So, with these variables, I can specify which directories are
> compressed into ramdisk image files and load them at boot time.
> Also, these variables allowed me to remove all of pre-defined
> directories (/etc, /dev, ...) from the pwl_target* scripts.  Only the
> initrd directories are built as required to make it boot.
> 
> Also, by specifying the partitions, we should be able to boot this
> from a small partition on the development drive...have to work out
> the lilo thing, but this looks like it would work...
> 
> Now, using these variables, the scripts build the following:
>   ramdisk.1  (compressed image of the $rd_mnt_1 variable)
>   ramdisk.2  (  ""                            2  ""     )
>   ramdisk.3  (  ""                            3  ""     )
>   linuxrc    (loads ramdisks ramdisk.1 ramdisk.2 ramdisk.3)
>   initrd     (as configured by linuxrc)
>   fstab      (filesystem table matches ramdisks as configured)
>   rc.init    (builds mtab to match the configuration)
>   lilo.conf (no change)
> 
> So far so good. The files seem to look like the previous files but
> match the configuration for the ramdisks.  I copied nearly all of
> your code or the at least the spirit of your code - of course,
> instead of the single 300+ line function, I have lots of little
> functions (sorry, old habits die hard :)
> 
> Still to do:
> 1. make this system boot
> -- have to build the ld.so.cache thing too
> 2. verify the size thing
> 3. add support for configured hard drive partitions
> 4. add the parameter setups
> 5. rework the other target devices that require ramdisks
> 
> And some questions:
> Is there some reason that /var is linked under /dev ?
> 
> Does the initrd use the same fstab (why is fstab built twice in the
> build_ro_root function ?)
> 
> Is the /home directory mirrored from a partition a common/desirable
> thing to do ?
> -- I'd need to define someway to specify that ramdisk=/home is not
> compressed by pwlconfig but copied at boot time from some other
> configured partition

I've modified the scripts to remove the /home partition and just leave
it in with the root fs. In my case I want the /home directory structure
to be read only in order to eliminate any possibility of the application
getting trashed. For permanent writable store, I create custom symbolic
links that point to the last partition that I mount as read write. What
you have described looks like it goes a long ways towards being able to
implement what I need in a generic fashion.
 
> Your thoughts ? Is this interesting or just something we need ?
> I'll try to get a system to boot today and send you a copy - or
> anyone else who is very brave, let me know...(of course, I'm out to
> BIOS world next week, so we can just let the code fester for a while
> :)

-- 
Dean Brown
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