[Voyage-linux] Comments about 0.6.2 and /rw /ro replacement by aufs a good idea? I don't think so ...

[Kim-man 'Punky' TSE]

Hi Beat,
> Yes but if you install packages in an ro fs you needs to know what to 
> do ...
> I have installed a lot of additional packages everytime I upgrade and 
> had never problem...
> Of course you must have a look at each package but now too (see below)
That is what I want to minimize the work and the need to review after 
installing package.

The problem we had is:  You install a package that creates an directory 
under /var/run, which is a symlink to /rw/var/run.  If you forget to 
create responding entry in ro, the created directories in /var/run will 
be lost after reboot.  There is another need to persist a read-write 
files after reboot, e.g. dhcpd.leases.
> That's the problem if you are out town for a long time :-(
> 0.5.2 has been a long time active until I could install it finally and 
> now 0.6.2 so I didn't hace noticed the discussion.
> But was is the solution to the /rw /ro problem?
It is supposed to be a replacement /rw /ro problem, if not, let me know 
what is needed to enhance.
> There are a lot of packages which need write access on some var file 
> OR others and of course in an embedded system which can die
> at every time you don't want your / system to be writeable and die in 
> the worst moment.
> So how can I enable write to some files?
So, is read-write files the feature you are asking for?
> That's the only problem I have. I don't not even need synchronizing 
> this files but I want a copy.
Some users need synchronizing and persist the file across the reboot.  
Perhaps you need a new feature VOYAGE_RW_DIRS or VOYAGE_VOLATILE_DIRS 
that just keep a copy and violatile.
> For example I need the following packages to run on voyage 0.6.2 as 
> noted already above:
> pdnsd : /var/cache/pdnsd
> dhcp3-server : /var/lib/dhcp3
> mrtg: /var/lib/mrtg
> How can I do that with 0.6.2??
>
> If you have to add about 10-20 dirs to VOYAGE_SYNC_DIRS for packages 
> you install you have to unterstand also
> what the packages needs and we are own the same as befor tmpfs BUT I 
> think this is not the idea behind tmps
> to have for every package an own tmpfs. 
VOYAGE_SYNC_DIRS only create mount points using -o bind, and all files 
are stored under /lib/init/rw. 
> Of course the right solution to this problem would be to but the WHOLE
> /var (as is the idea behind /var to be writtable) to VOYAGE_SYNC_DIRS 
> but than you have other problems.
>
> What I don't understand in the whole process. Does nobody install 
> addtitional packages and need this requirement?
For example, persist dhcpd.leases and some users need the sqlite or bdb 
files writabable and sync periodically to disk.
>
> Why not leave the /rw /ro issue as it was?
50% is my personal preference since manually maintaining the symlinks 
are ugly, 30% I want remove the old codes from pebble linux. 20% I want 
to re-implement it with a new way, using a simplified and generic 
mechanism.  

By removing /ro /rw and replaced with totally different things, it let 
me identify now well the new code works and allow me further enhance 
it.  So it leads to this discussion.
> Greetings
>
> Beat
-- 

Regards,
Punky

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