Re: Suggestions for remote admin of linux machines

From: George Patton (george_m_patton_at_yahoo.com)
Date: 05/19/04 

Date: Wed, 19 May 2004 15:27:04 -0500

Robert E A Harvey wrote:

> There are several home automation systems available, but all of them
> require you to have a _working_ system to dial into, to allow you to
> reboot your _broken_ system. Even if you purchase a dedicated remote
> management unit (esentially a modem with addressable switches) what
> are you going to do if that fails? This single point of failure will
> always exist.

Hmm. Are you basing this judgment on analysis of PC hardware designed
for home automation? If so, you need to look beyond PCs. Contact your
local security or burglar alarm distributor, and even electrical
wholesalers in some areas. *NOT* your local PC dealer.

The home automation boards that I've examined recently are essentially
standalone systems. Example: HAI and OnQ. In addition, I vaguely
recall that Leviton sells a standalone "lighting" controller that talks
with X10 switches and recepticals. HAI and OnQ controller installation
mechanics typically use a computer for programming so-called "zone
trigger" events -- although you could probably program these same zone
triggers via a keypad if you don't mind wasting your time -- but I don't
believe that any of these controllers *require* an on-site computer to
"dial into". To illustrate, HAI products can be controlled with
through a builtin ethernet port that would allow you to cycle
power/lights/etc on off from an ordinary web browser anywhere in the
world... although you would probably want to tunnel this access through
a suitable firewall. :-) Using a web interface for control, you would
need a computer to "dial from" while connecting to these controllers but
not a computer to dial "into". :-)

I've described previously how this kind of setup could be useful for the
administration of remote machines: power-cycling, video surveillance,
remote entry via electrically controlled door strikes, etc. Could this
be used to handle a crude reboot? "Hitting the big red switch, so to
speak"? Yes, if the bios has been set to allow booting on "power on"
and your boot-loader (grub for instance) has a suitable default OS in
the configuration file.

I'm more concerned about finetuning the system before, during, and after
reboot so that it can be reconfigured or retasked remotely. Apart from
using remote power-on/off features provided by networked UPS units, home
automation boards, etc, there are at least two solutions for bios-level
remote control. 1) KVM switches with IP interfaces: These appear to be
expensive on a per-port basis but I finally figured out last night that
I could use an inexpensive single port KVM/IP switch and CASCADE this
single port KVM/IP switch to ordinary (cheap) multiport KVM switches
costing much, much less. This reduces the per port cost significantly
while still allowing access via the internet. Startech in Canada makes
and sells this kind of switch. Features include a web interface and 128
bit SSL encryption.

http://www.startech.com

2) The other alternative would be a terminal server or computer with a
multiport serial card -- assuming that you have new machines that will
redirect bios communication to the serial port.

Could such hardware break down? Gee, let me think! :-) I suppose
that components of any system could fail eventually, and if the failure
occurs at a remote site, I suppose a technician would need to pay a
visit with replacement parts. Ditto for on-site failures. However, in
my experience software config problems are much more common than
hardware problems, and with the aforementioned tools in place I suspect
that I could do anything to the software on a remote system that I could
do to a system on my desktop... including reloading an entire operating
system from scratch.

> More expensive solutions include:
> http://www.webpowerswitch.com/

This solution seems relatively cheaper than the one I described and it's
a "turnkey" solution. The vendor doesn't provide specs, however, and I
suspect that it's rated for only 15A (total) if it's rated at all. I
called the company and asked the salesperson to read the UL label on the
back of the device and he informed me that there was no label. Not
good. This might be marginally acceptable for a single machine but not
for a small server farm in a commercial or government or educational
setting. By contrast, the solution that I described previously would
use multiple UL rated recepticals and/or switches that are rated for 15A
or 20A EACH.

I'm going to check out the watchdog solutions linked into your posting.
  Many thanks for posting them.

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