[asterisk-users] Build your own "appliance" concept

[Gordon Henderson]

On Thu, 6 Sep 2007, Jeremy P wrote:

> I've been working on this the past few days and thought I would put it out
> there to see if anyone else has interest in it.  It really has nothing to do
> with the Digium appliance, I've just been looking for some mass produced
> solid state hardware to run small branch offices off of for awhile now and I
> think I've finally landed on something I like.
>
> Basically I've taken an HP thin client workstation which is all solid state
> and loaded Debian and Asterisk on it (well, Asterisk-GUI too, but just to
> prove I could make it "appliance-worthy").  I'd be interested in any
> feedback on how to improve it, specifically on how to make Debian and
> Asterisk take up less space so I could buy the model that only has 512 MB of
> flash rather than 1 GB.

I built my own "appliance" some time back - initially for a router 
project, but I've since adapted it for Asterisk boxes and NAS boxes..

The basic unit has 64MB of IDE-flash, 256MB (or more) RAM. The flash IDE 
device has one partition and is bootable, so it has a /boot with a bzImage 
in it, enough of a /dev/ and /etc to make Lilo work on it and an initrd.gz 
which is unpacked into a 128MB RAM disk, then the system runs entirely 
from RAM once booted, so there's no continual write to flash issues (I 
hope!) I do actually have a 2nd partition on the device which I tar all 
the configuration files into - the bare minimal of what I need gets stored 
there whenever something changes. (and a copy of astdb too). I don't think 
this is perfect, and is prone to issues like a power cycle during write, 
but ...

I put a 2nd IDE flash device for Voicemail storage - that does have a live 
filesystem on it (currently just ext2, which I force an fsck of at boot 
time, if it's dirty) I've used 64MB to 256MB devices for this (storing VM 
in GSM format only), some customers want call recording, so they get the 
bigger ones, but I'm thinking of moving to a laptop drive for people who 
want even more (and enable idle spin down, etc.)

I build the kernel and initrd.gz file on a separate box - it's Debian, but 
it could be anything as I don't actually put a "distribution" as such into 
it, I just copy the files I need, and I'm lazy about it, so I copy all of 
/bin, /lib, most of /etc and a /dev and selected bits of /usr/bin and 
/usr/lib. (I use ldd on all the executables to work out which libraries I 
really need from /usr/lib) The kernel is a custom kernel for the hardware 
with no modules apart from Zaptel, etc.

I copy everything into a 128MB file, zeroed (it compresses better) 
formatted ext2, mounted as a lookback device. Once the copy is complete, I 
unmount it, gzip -9 it and that's the initrd.gz file. You need to make 
sure that the Linix kernel you compile has the ability to load an 
initrd.gz file and a big enough ramdisk!

It's not that efficient, and I could save space by using uClib, busybox, 
etc. but it's really not worth it, but 2 things I don't have on the target 
system is perl and vim.. Perl is about 10MB, as is vim. Right now I don't 
have a need for either (and I use nano when I do need to tweak stuff which 
is rarely) Perl would be nice so I could run stuff like mrtg locally on 
the boxes, but isn't essential for now.

So if there are some new security implications on the current Debian, or 
an asterisk upgrade, I just upgrade/update the build box, then create a 
new initrd.gz file and install it. (however this is in the order of 40MB 
for an Asterisk system with apache & php) so it a bit tricky to do a field 
upgrade if the remote system is bandwidth limited, but I can pull it in 
off a USB drive if necessary.

My /etc/asterisk and /var/www/docs are actually stored as part of the tar 
file, so upgrading those is fairly trivial.

This is what a running system looks like:

$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/ram0             124M  107M   18M  87% /
tmpfs                 125M     0  125M   0% /dev/shm
/dev/hdc2              60M   23M   37M  39% /data


If I mount the flash device, then:

# ls -l /mnt
total 39019
drwxr-xr-x   2 root root     1024 Aug  9 14:54 boot
drwxr-xr-x  13 root root    24576 Dec  6  2006 dev
drwxr-xr-x   2 root root     1024 Nov 15  2006 etc
-rw-r--r--   1 dsx  1000 39758472 Aug  9 14:53 image.gz
drwx------   2 root root    12288 Dec 12  2006 lost+found

# ls -l /mnt/boot
total 2849
-rw-r--r--  1 root root     512 Dec 12  2006 boot.0300
-rw-r--r--  1 root root     512 Dec 22  2006 boot.0800
-rw-r--r--  1 root root     512 Dec 12  2006 boot.1600
-rw-r--r--  1 dsx  1000 1390066 Jun  5 15:47 bzImage
-rw-------  1 root root   31744 Aug  9 14:54 map
-rw-r--r--  1 root root   98728 Sep 21  2006 memtest86+.bin
-rw-r--r--  1 root root     241 Oct 28  2006 message

Because everything is in RAM, it's actually quite fun to "play" with 
trying to destroy it :) Eg.

   # cd / ; rm -rf *

then just reboot it to recover...

The one thing that's not "appliance" about it is the box - it's still a PC 
at the end of the day, but I guess when I'm churning out 100's of these I 
can afford a custom case design ;-)

Those HP boxes do look nice though, but they're more expensive that I 
build my own for (in the UK at least!) but I do have the option of wall 
mount, desktop or rackmount cases I guess...

Gordon