Re: [gentoo-user] Managing multiple systems with identical hardware

[Grant <emailgrant@gmail.com>]

>> I'm about to embark on this (perilous?) journey and I'm wondering if
>> anyone would make a comment on any of the questions in the last
>> paragraph below.  This is basically my plan for setting up a bunch of
>> systems (laptops) in an office which are hardware-identical to my own
>> laptop and creating a framework to manage them all with a bare minimum
>> of time and effort.
>>
>> Thanks,
>> Grant
>>
>>
>>>>>>>> I see what you desire now - essentially you want to clone your laptop
>>>>>>>> (or big chunks of it) over to your other workstations.
>>>
>>> I've been working on this and I think I have a good and simple plan.
>>>
>>> My laptop roams around with me and is the "master" system.  The office
>>> router is the "submaster" system.  All of the other office systems are
>>> "minion" systems.  All of the systems are 100% hardware-identical
>>> laptops.  All of the minions are 100% software-identical.
>>>
>>> I install every package that any system needs on the master and create
>>> an SSH keypair.  The only config files that change from their state on
>>> the master are: /etc/conf.d/hostname, /etc/conf.d/net,
>>> /etc/ssh/sshd_config, /etc/shorewall/*.  I write comments in those
>>> files which serve as flags for scripted changes.
>>>
>>> I write a script that is run from the master to the submaster, or from
>>> the submaster to a minion.  If it's the former, rsync / is run with
>>> exceptions (/usr/portage, /usr/local/portage, /var/log, /tmp, /home,
>>> /root but /root/.ssh/id_rsa_script* is included), my personal user is
>>> removed, a series of workstation users are created with useradd -m,
>>> services are added or removed from /etc/runlevels/default, and config
>>> files are changed according to comment flags.  If it's the latter,
>>> rsync / is run without exceptions, services are added or removed from
>>> /etc/runlevels/default, and config files are changed according to
>>> comment flags.
>>>
>>> All user info on the submaster and minions would be effectively reset
>>> whenever the script is run and that's fine.  Root logins would have to
>>> be allowed on the submaster and minions but only with the SSH key.
>>> There are probably more paths to exclude when rsyncing master to
>>> submaster.
>>>
>>> That's it.  No matter how numerous the minions become, this should
>>> allow me to keep everything running by administrating only my own
>>> system, pushing that to the submaster, and having the submaster push
>>> to the minions.  I've been going over the nitty-gritty and everything
>>> looks good.
>>>
>>> What do you think?  Is there anything inherently wrong with rsyncing /
>>> onto a running system?  If there are little or no changes to make,
>>> about how much data would actually be transferred?  Is there a better
>>> tool for this than rsync?  I know Funtoo uses git for syncing with
>>> their portage tree.
>>>
>>> - Grant
>>
>
> Only thing that comes immediately to mind in rsyncing an overwrite of
> / is that any process that's running that goes looking for libraries
> or other data after the rsync pulls the rug out from beneath it might
> behave erratically, crash, kick a puppy, write arbitrary data all over
> your drive. Also, it's somewhat important to be careful about the
> various not-really-there mounts, /dev, /sys, /proc... /run's probably
> touchy too, and /var has a few pieces that might be in use mid-sync
> and choke something along the way. My idea on that would be... build
> an initramfs that:

What if the push is done while no one is logged in to the system(s)
being updated?  I could also exclude /dev, /sys, /proc, and /run and
reboot after the update.  If that's not good enough, what if I boot
the systems being updated into read-only mode before updating them?
I'm hoping to keep the process as simple as possible.

- Grant


> 1) boots to a script
>   a) warns the user that it's hungry and that feeding it will be
> dangerous to any non-backed-up data, with prompt
>   b) warns the user again, with prompt ('cause watching an rsync roll
> by that eats that document you just spent 3 weeks on isn't fun)
> 2) mounts / in a working directory
> 3) rsyncs the new data from the sub-master
> 4) kicks off a script to update a hardware keyed (mac address is good
> for this) set of settings (hostname, etc)
> 5) reboots into the new system.
>
> For extra credit... sync /home back to the sub-master to prevent
> overfeeding the beast.
>
> --
> Poison [BLX]
> Joshua M. Murphy