We have satellite modems and small servers installed in plenty of odd, rough, remote rural places, and satellite modems can be persnickety beasts. The provider claims they're all identical but some hand out static IP's over dhcp, some don't. Some respond to DHCP, some don't. They all have a nice parse-able web interface for runtime statistics, but not always the same parse-able web interface for runtime statistics. Trying to deal with their eccentricities in an automatic way can be a bit troubling if you want a uniform set of systems.
With a bit of wrangling I found an arrangement that worked in most situations. Usually the modems give a static address over DHCP, or a NAT address over DHCP, but a few odd ones don't respond at all, so I used dhcp failovers to auto-set the server's WAN port to an 192.168.x.x address when DHCP failed. Finally I could have the same settings work on all of my servers and modems, with actual static IP's when available, and it was good.
A little while later, a minor but important security fix came through for dhcpcd. In-house testing showed it properly picking up IP's, and the rest of the changes looked absolutely minor, so I deployed it. Most servers kept running... a few didn't. 100km later I was sitting on a bucket in a grimy, tick-filled wooden shack trying to figure out what the machine in front of me was doing to itself.
Code:
$ ifconfig wan
wan Link encap:Ethernet HWaddr 00:08:C7:E3:A1:13
inet addr:169.254.32.239 Bcast: ...
The not-so-insignificant new feature turned out to be zeroconf support, enabled by default. This means failure is a perfectly acceptable outcome for dhcpcd now. On timeout it sets a useless random IP and returns success. No error, no failover; no failover, no network connection. One extra flag in dhcpcd's default options, a few long drives, and everything worked fine again.
I don't want to kill whoever decided zeroconf was a sane default for the world, but I'd at least like to pie him.
Last edited by Corona688; 01-13-2012 at 01:16 PM..
seesat5(1) General Commands Manual seesat5(1)NAME
seesat5 - provides satellite visibility information.
SYNOPSIS
seesat5 [ report ] [ go <Label> ] | [ <command> ... ]
DESCRIPTION
This program uses the sgp4 algorithm provided by NORAD to produce position information on a satellite. Seesat5 can produce tracking infor-
mation for one satellite over a period of several days, or for a collection of satellites over that period. By providing filter conditions
seesat5 prints out only those satellites you might have a chance to see rather than all the satellites that pass above the horizon.
Seesat5 is typically run by placing control commands into an init file called SEESAT5.INI. See seesat5 (7) for the description of these
commands. If there is no init file Seesat5 will present the operator with a '>' prompt where commands can be entered. From the prompt
seesat5 will begin analysis when sufficient parameters have been entered to begin the run.
Seesat5 uses selection conditions to filter the data so that only high and bright satellites are printed. Note that the selection condi-
tions are used to select whether or not the current passes data will be printed. If it is printed, then the complete pass data is printed.
ie. all data from when the satellite comes over the horizon until it goes below.
For lines that satisfied ALL the selection conditions, a "+" sign is printed as the first character.
Options
report This option will disable printing of report records in the output of the run. These include all command lines found in SEESAT5.INI
or entered from the command line or the prompt.
go Followed by a label, this option causes branching within the SEESAT5.INI to begin execution at the line following label. Branching
occurs when the cmdline command is executed in the SEESAT5.INI file.
command
Most of the commands that can be found in SEESAT5.INI can be entered on the command line. If you desire the SEESAT5.INI file to exe-
cute after the command line be sure to make the last command RET.
FILES
SEESAT5.INI
The control file for seesat5
*.tle Two line element files used by seesat5.
SEE ALSO seesat5(7), SEESAT5.INI(5), tle(5), cr(1)BUGS
Seesat5 is not always able to check data integrity. Since computation and output is driven by the data in the two line element, subtle
errors in a tle can cause floating point exceptions. In addition there are several commands that do not work well together, like SHOWTLE
and RUNTIME. Please report any problems with seesat5 to Dale Scheetz <dwarf@polaris.net>.
Debian Linux 28 March 96 seesat5(1)
01-13-2012
