Re: Install Firefox
Hi Jerry this is just for the record on the list. It worked. Thank you very much. I now have firefox working. Now I need to make adobe_flash to work with it. -basanta On Mon, Jun 3, 2013 at 7:52 PM, Jerry Vonau jvo...@shaw.ca wrote: On Mon, 2013-06-03 at 14:29 +0545, Basanta Shrestha wrote: It was reading repository information from file:///root/local but packages were not installed. On Mon, Jun 3, 2013 at 2:02 PM, Basanta Shrestha basanta.shres...@olenepal.org wrote: On Mon, Jun 3, 2013 at 10:30 AM, Basanta Shrestha basanta.shres...@olenepal.org wrote: On Sat, Jun 1, 2013 at 12:40 AM, Jerry Vonau jvo...@shaw.ca wrote: On Fri, 2013-05-31 at 11:14 +0545, Basanta Shrestha wrote: Adding fedora=fedora_update and rebuilding didn't work. Jerry, As you suggested it installed all the required newer firefox,xulrunner and nss... packages but the resulting image couldn't boot the XO. Now I am going for your second suggestion. I have created a local repo for firefox, xulrunner and other dependencies( 9 altogether) . Could you please check if the entries are right? Well I'm surprised that I'm the only one to answer this, I gave the others ample time to respond. yes, looks like no one takes pride on answering simple questions ;) /root/local/.repo Where did you download the rpms to? Was it /root/local/? Did you run createrepo /root/local/? yes to /root/local/ and I have done createrepo. -- [local] name=firefox-xulrunner local baseurl=file:///root/local/ gpgcheck=0 enabled=1 -- I don't understand, what are you doing with the above code? olpc-os-12.1.0-xo1.75.ini Right below [repos] section -- [custom_repo] local=1,firefox,file:///root/local/ -- No, don't do that, you have to use the OOB method of naming the repos in [repos]. I was following this documentation http://cainmanor.com/tech/build-a-custom-repository-for-centos/ and they had this extra step to create .repo file. so . [repos] fedora_arch=i386 olpc_frozen_1=0,koji.dist-f17-i686 olpc_frozen_2=0,koji.dist-f17-i686-updates-12.1.0 olpc_frozen_3=1,local.12.1.0 olpc_frozen_4=1,local.12.1.0-xo1.5 custom_repo_1=0,firefox,file:///root/local/ add_excludes_to=koji.dist-f17-i686,koji.dist-f17-i686-updates-12.1.0 When you run osbuilder.py, early into the routine you can see the repos being contacted, check to see if your new one is being used or there is an error present. The repo seems to be working now it is retrieving packages form local repo. Thanks Jerry you have been a great help for me. Well it was trying to retrieving from file://root/local but it didn't install any package. Wonder what is wrong. Just like you used yum to install firefox in the field, did you ask OOB to install firefox? In your ini file you need to use: [custom_packages] add_packages=firefox Jerry Jerry
School networks and electrical equipment damage
Hi, Those of us familiar with setting up school networks (server + switch + APs) in some of our deployments will be familiar with the occasional loss of hardware, due to surges in the low quality electrical supply or whatever, even when the system is protected by a cheap UPS which supposedly offers some protection. This has often been the case in Nicaragua, so the group is now buying more expensive UPSes, PoE switches, and PoE access points for new schools. This means that the server and switch are connected to mains power via a UPS which hopefully protects them, and none of the APs are connected directly to the mains (instead they get Power over Ethernet) which hopefully offers some isolation from bad electrical conditions. This equipment is expensive, especially in places like Nicaragua where lots of import taxes are applied. But the hope is that the investment pays off in that the equipment doesn't get zapped. However, one week after deploying this equipment in the first school, we are left with a server that doesn't boot, 3 out of 4 access points broken with a nice burning electronics smell, and a broken switch with a lot of visible damage to the electronics. And the most surprising thing - we had not even turned on the network yet, pending some electrical work. Everything was connected up except one crucial link - the UPS was not plugged into mains power. So all of this damage happened without any of the devices having a connection to the mains. Connectivity-wise, the setup was: WAN: Phone line - ADSL modem - XS LAN: XS - Switch - 4 APs And power connections: the XS, ADSL modem and switch were connected to the UPS. The APs were connected to the switch over ethernet for both power and data. Again, since the battery was not connected to mains power, none of the devices had a power source. The connectivity engineer's best bet is that a lightening bolt landed at the school or nearby, and that this caused a power surge on the phone line. This surge passed through the ADSL modem, server, switch, and 4 APs, destroying everything in its path (except 1 AP that was connected over a longer cable than the rest). I figured this is a story worth sharing, for any other projects considering splashing out on more expensive equipment... Also, I'm wondering if anyone has any advice/experience here. Would others expect this more expensive setup to be more resilient to bad electrical conditions than a cheaper setup - will the investment pay off? I figure that the case of a lightening bolt might be a bit extreme, but electrical storms are a nightly occurance here almost daily during the 6 month rainy season. I have seen that some UPSs (unfortunately not these ones) allow a phone line to be passed through them, supposedly offering some protection. Would such a system protect against a lightening bolt, assuming thats what happened here? Thanks Daniel ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: School networks and electrical equipment damage
The connectivity engineer's best bet is that a lightening bolt landed at the school or nearby, and that this caused a power surge on the phone line. This surge passed through the ADSL modem, server, switch, This sounds remarkably plausable to me ;-) I've had hardware problems due to lightning strikes in the USA - years ago, I lost an ethernet hub due to a surge on a 10base2 cable, from a strike a block away. I've seen modems and printers fried from lightning surges - anything with a long cable becomes a transformer. Recently, I've lost phone service because the lightning protectors got fried my the house-side box (normally they self-reset). Every phone termination point (the telco box on the side of your house) in the USA has lightning protection in it (or at least should ;). If that's not the case for other countries, at least cheap surge protectors should be used on anything with a phone wire connected to it. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: School networks and electrical equipment damage
On Thu, Jun 6, 2013 at 9:58 PM, Daniel Drake d...@laptop.org wrote: Hi, Those of us familiar with setting up school networks (server + switch + APs) in some of our deployments will be familiar with the occasional loss of hardware, due to surges in the low quality electrical supply or whatever, even when the system is protected by a cheap UPS which supposedly offers some protection. This has often been the case in Nicaragua, so the group is now buying more expensive UPSes, PoE switches, and PoE access points for new schools. This means that the server and switch are connected to mains power via a UPS which hopefully protects them, and none of the APs are connected directly to the mains (instead they get Power over Ethernet) which hopefully offers some isolation from bad electrical conditions. This equipment is expensive, especially in places like Nicaragua where lots of import taxes are applied. But the hope is that the investment pays off in that the equipment doesn't get zapped. However, one week after deploying this equipment in the first school, we are left with a server that doesn't boot, 3 out of 4 access points broken with a nice burning electronics smell, and a broken switch with a lot of visible damage to the electronics. And the most surprising thing - we had not even turned on the network yet, pending some electrical work. Everything was connected up except one crucial link - the UPS was not plugged into mains power. So all of this damage happened without any of the devices having a connection to the mains. Connectivity-wise, the setup was: WAN: Phone line - ADSL modem - XS LAN: XS - Switch - 4 APs And power connections: the XS, ADSL modem and switch were connected to the UPS. The APs were connected to the switch over ethernet for both power and data. Again, since the battery was not connected to mains power, none of the devices had a power source. The connectivity engineer's best bet is that a lightening bolt landed at the school or nearby, and that this caused a power surge on the phone line. This surge passed through the ADSL modem, server, switch, and 4 APs, destroying everything in its path (except 1 AP that was connected over a longer cable than the rest). I figured this is a story worth sharing, for any other projects considering splashing out on more expensive equipment... Also, I'm wondering if anyone has any advice/experience here. Would others expect this more expensive setup to be more resilient to bad electrical conditions than a cheaper setup - will the investment pay off? I figure that the case of a lightening bolt might be a bit extreme, but electrical storms are a nightly occurance here almost daily during the 6 month rainy season. I have seen that some UPSs (unfortunately not these ones) allow a phone line to be passed through them, supposedly offering some protection. Would such a system protect against a lightening bolt, assuming thats what happened here? What is the grounding of the electrical setup there? You may want to invest in having a separate grounding rod installed specifically for the circuit the network equipment is on and possibly a lighting rod. When we built out a small data center in Alewife we actually had the building install a lightning rod on the roof with a dedicated ground circuit to help protect our circuits in the building. In general I have found that more expensive network equipment handles dirty power a bit better than the cheap stuff. As for lightning and other larger power surges, all of it fries about the same. For POE WAP's I would suggest looking at the Ubiquiti lineup. I have a couple of Picostation2's and a Nanostation M2 and have very impressed with their coverage and stability for the price. They are also indoor/outdoor certified. -Jon ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: School networks and electrical equipment damage
d...@laptop.org said: I have seen that some UPSs (unfortunately not these ones) allow a phone line to be passed through them, supposedly offering some protection. Would such a system protect against a lightening bolt, assuming thats what happened here? Surge suppressor is the buzzword you are looking for. They will help, but nothing will stop a lightning strike that is near enough. The only question is how-near. The wiki page looks good: http://en.wikipedia.org/wiki/Surge_suppressor Note the discussion about MOVs getting used up. Some outlet strips include a pair of phone jacks and/or cable TV connectors. That's the quick, simple, and low cost approach. You can also get industrial type units at higher prices. Google has lots of hits. I'm far from a wizard in this area. How many schools are you talking about? If it's more than 2 or 3, it might be worth a phone call to one of the non-cheap places to see if they have suggestions. (Or see if they have some documentation on the web.) -- These are my opinions. I hate spam. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: School networks and electrical equipment damage
On Thu, Jun 6, 2013 at 5:54 PM, Hal Murray hmur...@megapathdsl.net wrote: d...@laptop.org said: I have seen that some UPSs (unfortunately not these ones) allow a phone line to be passed through them, supposedly offering some protection. Would such a system protect against a lightening bolt, assuming thats what happened here? Surge suppressor is the buzzword you are looking for. They will help, but nothing will stop a lightning strike that is near enough. The only question is how-near. The wiki page looks good: http://en.wikipedia.org/wiki/Surge_suppressor Note the discussion about MOVs getting used up. Some outlet strips include a pair of phone jacks and/or cable TV connectors. That's the quick, simple, and low cost approach. You can also get industrial type units at higher prices. Google has lots of hits. One thing to look out for with the outlet strips is band limiting on the signal as it passes through; probably not an issue here, but worth testing. -walter I'm far from a wizard in this area. How many schools are you talking about? If it's more than 2 or 3, it might be worth a phone call to one of the non-cheap places to see if they have suggestions. (Or see if they have some documentation on the web.) -- These are my opinions. I hate spam. ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel -- Walter Bender Sugar Labs http://www.sugarlabs.org ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: School networks and electrical equipment damage
On Thu, Jun 06, 2013 at 01:58:58PM -0600, Daniel Drake wrote: And the most surprising thing - we had not even turned on the network yet, pending some electrical work. Everything was connected up except one crucial link - the UPS was not plugged into mains power. So all of this damage happened without any of the devices having a connection to the mains. Actually not plugged in? The whole network was therefore either isolated from building electrical earth (ground) or had a series of surreptitious connections, the critical one being the telephone line. Hmm. Lightning wasn't necessary. Here's my theory: Each long run of ethernet twisted pair becomes one side of a capacitor, the other side being the building wiring, piping, or structure. The long run of telephone wire picks up static charge from wind, lightning ground currents, test currents from the telephone exchange or line workers, or induced currents from other subscribers or power network switching. Even turning on many lights. http://www.pololu.com/docs/0J16/all can give you an idea of what can happen. Any of these events will induce a starting pulse of DC in the telephone wire, which is analogous to the length of DC power cable in the Pololu explanation; the inductor. The low equivalent series resistance (ESR) capacitor can be thought of as the long cabling against the building. As a result of the capacitor and the inductor, the voltage is amplified until it reaches the breakdown voltage of whatever is connected. Having the UPS plugged in might have prevented this voltage from finding a route through something more precious. Instead, it might have found a route through a series of surge protection devices in the UPS, and then the only damaged equipment would be the ADSL modem. The convention is to build from the ground up. Don't plug the cables in until the ground is available, and then plug them in in strict order. People get away with not doing this because the damaging pulse isn't constant. (Reminds me of the time that I pulled a UPS input power plug out instead of just turning it off. A bad idea. The last pin to separate was active. The connected equipment lost ground reference, the only ground reference that remained was through a device, so it took a full hit and died. The resulting current passed into the building ground, and triggered the earth leakage breaker on the circuit that the UPS was originally connected to. Other equipment connected to that circuit powered down.) (Reminds me also of working for a cable contractor in the 1980s, looking after their cable management system on a VAX ... they were putting millions of cables into a power station, and the build was done from the ground up; that is cables were tracked as to whether they had been terminated yet, and the list of unterminated cables was a special report from the database that they always wanted to see.) I have seen that some UPSs (unfortunately not these ones) allow a phone line to be passed through them, supposedly offering some protection. Would such a system protect against a lightening bolt, assuming thats what happened here? Yes, but only if the UPS was earthed. It would also protect the ADSL modem. It would also protect from most other causes of a current pulse arriving on the phone line. -- James Cameron http://quozl.linux.org.au/ ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
ANNOUNCEMENT XSCE 0.3 Final Release
After three months of hard work and three weeks of working out the kinks in the release process, XSCE 0.3 is ready for its final release. We went conservative this release. Emphasis on stability meant less time for new features. * XSCE now runs on the XO-1.5,XO-1.75 and XO-4. * Modular Architecture: cleanly integrate extendable services. * XSCE runs on the XOs' current OS 13.1.0 (we discovered some wrinkles with 13.2.0 which push its use off to the next release) * Moodle is Back! * Content filtering via openDNS.com * Script for formatting of SD cards, and integration into system for content storage and memory extending swap file (does not work on XO4's) Grab an XO-1.5, XO-1.75 or a XO-4 to give XSCE 0.3 give a whirl: http://schoolserver.org/0.3 If you are just getting started with XSCE we suggest using the instruction at http://wiki.laptop.org/go/User:Holt/XS_Community_Edition/0.3/Installingto install your first server. Once you are through the install, a good second step is to work your new server though it’s paces by doing the smoke test at http://wiki.laptop.org/go/User:Holt/XS_Community_Edition/0.3/Testing Monster thanks to everyone who spent months of springtime work -- traveling days from quite different parts of North America to make this community product real. George Hunt ___ support-gang mailing list support-g...@lists.laptop.org http://lists.laptop.org/listinfo/support-gang ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
School networks and electrical equipment damage
Hi All As James has pointed out, there are many ways to fry a network. But having a telephone line connected to a modem which is in turn connected to LAN cables is one of the most problematic arrangements. I used to work for a telco where one of our jobs was providing phone services into power substations where both lightning strikes and power ground faults produce similar problems. The problem is that the telephone line represents an earth at a point a long way from the actual installation, nominally at the telephone exchange. So a lightning strike anywhere in the area can produce a large voltage differential between the phone line and the local equipment which is effectively tied to the local earth (even if the mains is not plugged in). A three element gas arrestor fitted to the incoming phone line and **effectively earthed** to the centre electrode can be effective in clamping the phone line to the local ground, thus preventing the equipment seeing the differential. But effectively earthed is the key phrase. The earth connection must be low resistance and low inductance - so no long earth wires, the gas arrestor has to be almost at the earth stake. In practice it is quite difficult to get these installations done correctly so that they are really effective. One approach for 'repeat offenders' in problem areas, in addition to fitting gas arrestors to the phone line and surge suppressors to the mains to deal with as much of the problem as possible, is to isolate the ADSL modem from the rest of the local network. A wifi link is one effective way to do this. Have no LAN cables at all connected to the modem. Use a wifi link from the modem to the network switch, then run cables from the switch. In the event of a lightning strike, the modem is sacrificed, but the high voltages from the phone line can't get into the rest of the equipment. (And keep a spare modem, pre-configured in the cupboard). A similar issue exists with running LAN cables between buildings on a campus. Long LAN cables make great aerials as James points out, and will pick up a lot of energy from nearby lightning strikes. One solution is to use wifi to link buildings rather than cables. Fibre optic links are also very effective. Regards Terry ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: School networks and electrical equipment damage
On Jun 6, 2013, at 3:58 PM, Daniel Drake wrote: Those of us familiar with setting up school networks (server + switch + APs) in some of our deployments will be familiar with the occasional loss of hardware, due to surges in the low quality electrical supply or whatever, even when the system is protected by a cheap UPS which supposedly offers some protection. This has often been the case in Nicaragua, so the group is now buying more expensive UPSes, PoE switches, and PoE access points for new schools. This means that the server and switch are connected to mains power via a UPS which hopefully protects them, and none of the APs are connected directly to the mains (instead they get Power over Ethernet) which hopefully offers some isolation from bad electrical conditions. This equipment is expensive, especially in places like Nicaragua where lots of import taxes are applied. But the hope is that the investment pays off in that the equipment doesn't get zapped. However, one week after deploying this equipment in the first school, we are left with a server that doesn't boot, 3 out of 4 access points broken with a nice burning electronics smell, and a broken switch with a lot of visible damage to the electronics. And the most surprising thing - we had not even turned on the network yet, pending some electrical work. Everything was connected up except one crucial link - the UPS was not plugged into mains power. So all of this damage happened without any of the devices having a connection to the mains. Connectivity-wise, the setup was: WAN: Phone line - ADSL modem - XS LAN: XS - Switch - 4 APs And power connections: the XS, ADSL modem and switch were connected to the UPS. The APs were connected to the switch over ethernet for both power and data. Again, since the battery was not connected to mains power, none of the devices had a power source. The connectivity engineer's best bet is that a lightening bolt landed at the school or nearby, and that this caused a power surge on the phone line. This surge passed through the ADSL modem, server, switch, and 4 APs, destroying everything in its path (except 1 AP that was connected over a longer cable than the rest). This was my most likely hypothesis as well. I believe the damage would have been less had the UPS actually been plugged in, but most probably have their input protected, not their outputs! I figured this is a story worth sharing, for any other projects considering splashing out on more expensive equipment... Also, I'm wondering if anyone has any advice/experience here. Would others expect this more expensive setup to be more resilient to bad electrical conditions than a cheaper setup - will the investment pay off? Cat5 Ethernet transformers generally provide 1.5 kV of isolation (at each end) but PoE breaks that. I believe the actual protection provided by the UPS can vary widely. They are usually required in situations like yours to protect the hard drivers, not as much for power line protection. I would use a periodically replaced surge protector before it and maybe a surge protected power strip after it. I figure that the case of a lightening bolt might be a bit extreme, but electrical storms are a nightly occurance here almost daily during the 6 month rainy season. Nothing will protect against a direct lightning strike of the wire. The more common case is a strike near the wire or the central office which can induce still induce many kV of surge on the lines. If electrical storms are common you need to take precautions. I hope all the network cabling is indoors ? If it is only partially so, consider something like: http://www.l-com.com/surge-protector-indoor-4-port-med-power-10-100-base-t-cat5-lightning-surge-protector I have seen that some UPSs (unfortunately not these ones) allow a phone line to be passed through them, supposedly offering some protection. Would such a system protect against a lightening bolt, assuming thats what happened here? Probably not. Primary protection on the phone line should be an gapped carbon block or gas tube protector at the entrance to the building between each line of the phone pair and a good ground.These protect against higher energy surges, and generally kick in at over 1 kV. I would suggest using primary protection that includes secondary protection, such as you see in: http://www.l-com.com/surge-protector-outdoor-high-power-telephone-dsl-lightning-surge-protector-screw-terminals You could also loop it through the UPS at this point for redundancy (but it MUST remain plugged in to provide protection --- it not, it makes things worse!) Then there is the protection in the modem itself, which should be able to handle the remaining surge. They are so common in telephony as to be required --- but primary protection and proper grounding is always assumed. Sorry to hear about your misfortunes, wad
Re: [support-gang] ANNOUNCEMENT XSCE 0.3 Final Release
Good news indeed and my appreciation to all the hard work the XSCE team have put into. I recently installed R2 on SD a card for XO 1.75 (512 Mib) with 3 APs. It seems to be working fine with 30 XO-1s connected via different AP. Registration went well, ejabberdctl displayed registered users, moodle work, backup work. So I am a happy end-user waiting to see it deployed in the wild soon! T.K. Kang -Original Message- From: George Hunt [mailto:georgejh...@gmail.com] Sent: Friday, June 7, 2013 08:07 AM To: 'Community Support Volunteers -- who help respond to help AT laptop.org' Cc: 'Support Gangsters', 'server-devel', 'Testing', 'IAEP SugarLabs', de...@laptop.org Subject: [support-gang] ANNOUNCEMENT XSCE 0.3 Final Release After three months of hard work and three weeks of working out the kinks in the release process, XSCE 0.3 is ready for its final release. We went conservative this release. Emphasis on stability meant less time for new features. * XSCE now runs on the XO-1.5,XO-1.75 and XO-4. * Modular Architecture: cleanly integrate extendable services. * XSCE runs on the XOs' current OS 13.1.0 (we discovered some wrinkles with 13.2.0 which push its use off to the next release) * Moodle is Back! * Content filtering via openDNS.com * Script for formatting of SD cards, and integration into system for content storage and memory extending swap file (does not work on XO4's) Grab an XO-1.5, XO-1.75 or a XO-4 to give XSCE 0.3 give a whirl: http://schoolserver.org/0.3 If you are just getting started with XSCE we suggest using the instruction at http://wiki.laptop.org/go/User:Holt/XS_Community_Edition/0.3/Installingto install your first server. Once you are through the install, a good second step is to work your new server though it’s paces by doing the smoke test at http://wiki.laptop.org/go/User:Holt/XS_Community_Edition/0.3/Testing Monster thanks to everyone who spent months of springtime work -- traveling days from quite different parts of North America to make this community product real. George Hunt ___ support-gang mailing list support-g...@lists.laptop.org http://lists.laptop.org/listinfo/support-gang ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
Re: School networks and electrical equipment damage
I considered sources such as James' theory, as well as someone connecting one of the ethernet cables to line voltage, and neither accounted for the level of damage you described. But I can't agree more with James' point about building from the ground up. The first thing we used to wire up in a computer room was the frame grounds --- with modern SOHO gear that all comes through the grounded power plug. But it has to be plugged in to be grounded (i.e. protected). Coincidentally, today I checked out the earth ground in the new hardware office and wired up the workbench grounding in OLPC Boston's new digs in Davis Sq. wad On Jun 6, 2013, at 6:51 PM, James Cameron wrote: On Thu, Jun 06, 2013 at 01:58:58PM -0600, Daniel Drake wrote: And the most surprising thing - we had not even turned on the network yet, pending some electrical work. Everything was connected up except one crucial link - the UPS was not plugged into mains power. So all of this damage happened without any of the devices having a connection to the mains. Actually not plugged in? The whole network was therefore either isolated from building electrical earth (ground) or had a series of surreptitious connections, the critical one being the telephone line. Hmm. Lightning wasn't necessary. Here's my theory: Each long run of ethernet twisted pair becomes one side of a capacitor, the other side being the building wiring, piping, or structure. The long run of telephone wire picks up static charge from wind, lightning ground currents, test currents from the telephone exchange or line workers, or induced currents from other subscribers or power network switching. Even turning on many lights. http://www.pololu.com/docs/0J16/all can give you an idea of what can happen. Any of these events will induce a starting pulse of DC in the telephone wire, which is analogous to the length of DC power cable in the Pololu explanation; the inductor. The low equivalent series resistance (ESR) capacitor can be thought of as the long cabling against the building. As a result of the capacitor and the inductor, the voltage is amplified until it reaches the breakdown voltage of whatever is connected. Having the UPS plugged in might have prevented this voltage from finding a route through something more precious. Instead, it might have found a route through a series of surge protection devices in the UPS, and then the only damaged equipment would be the ADSL modem. The convention is to build from the ground up. Don't plug the cables in until the ground is available, and then plug them in in strict order. People get away with not doing this because the damaging pulse isn't constant. (Reminds me of the time that I pulled a UPS input power plug out instead of just turning it off. A bad idea. The last pin to separate was active. The connected equipment lost ground reference, the only ground reference that remained was through a device, so it took a full hit and died. The resulting current passed into the building ground, and triggered the earth leakage breaker on the circuit that the UPS was originally connected to. Other equipment connected to that circuit powered down.) (Reminds me also of working for a cable contractor in the 1980s, looking after their cable management system on a VAX ... they were putting millions of cables into a power station, and the build was done from the ground up; that is cables were tracked as to whether they had been terminated yet, and the list of unterminated cables was a special report from the database that they always wanted to see.) I have seen that some UPSs (unfortunately not these ones) allow a phone line to be passed through them, supposedly offering some protection. Would such a system protect against a lightening bolt, assuming thats what happened here? Yes, but only if the UPS was earthed. It would also protect the ADSL modem. It would also protect from most other causes of a current pulse arriving on the phone line. -- James Cameron http://quozl.linux.org.au/ ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel ___ Devel mailing list Devel@lists.laptop.org http://lists.laptop.org/listinfo/devel
[Server-devel] School networks and electrical equipment damage
Hi, Those of us familiar with setting up school networks (server + switch + APs) in some of our deployments will be familiar with the occasional loss of hardware, due to surges in the low quality electrical supply or whatever, even when the system is protected by a cheap UPS which supposedly offers some protection. This has often been the case in Nicaragua, so the group is now buying more expensive UPSes, PoE switches, and PoE access points for new schools. This means that the server and switch are connected to mains power via a UPS which hopefully protects them, and none of the APs are connected directly to the mains (instead they get Power over Ethernet) which hopefully offers some isolation from bad electrical conditions. This equipment is expensive, especially in places like Nicaragua where lots of import taxes are applied. But the hope is that the investment pays off in that the equipment doesn't get zapped. However, one week after deploying this equipment in the first school, we are left with a server that doesn't boot, 3 out of 4 access points broken with a nice burning electronics smell, and a broken switch with a lot of visible damage to the electronics. And the most surprising thing - we had not even turned on the network yet, pending some electrical work. Everything was connected up except one crucial link - the UPS was not plugged into mains power. So all of this damage happened without any of the devices having a connection to the mains. Connectivity-wise, the setup was: WAN: Phone line - ADSL modem - XS LAN: XS - Switch - 4 APs And power connections: the XS, ADSL modem and switch were connected to the UPS. The APs were connected to the switch over ethernet for both power and data. Again, since the battery was not connected to mains power, none of the devices had a power source. The connectivity engineer's best bet is that a lightening bolt landed at the school or nearby, and that this caused a power surge on the phone line. This surge passed through the ADSL modem, server, switch, and 4 APs, destroying everything in its path (except 1 AP that was connected over a longer cable than the rest). I figured this is a story worth sharing, for any other projects considering splashing out on more expensive equipment... Also, I'm wondering if anyone has any advice/experience here. Would others expect this more expensive setup to be more resilient to bad electrical conditions than a cheaper setup - will the investment pay off? I figure that the case of a lightening bolt might be a bit extreme, but electrical storms are a nightly occurance here almost daily during the 6 month rainy season. I have seen that some UPSs (unfortunately not these ones) allow a phone line to be passed through them, supposedly offering some protection. Would such a system protect against a lightening bolt, assuming thats what happened here? Thanks Daniel ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] School networks and electrical equipment damage
On Thu, Jun 06, 2013 at 01:58:58PM -0600, Daniel Drake wrote: And the most surprising thing - we had not even turned on the network yet, pending some electrical work. Everything was connected up except one crucial link - the UPS was not plugged into mains power. So all of this damage happened without any of the devices having a connection to the mains. Actually not plugged in? The whole network was therefore either isolated from building electrical earth (ground) or had a series of surreptitious connections, the critical one being the telephone line. Hmm. Lightning wasn't necessary. Here's my theory: Each long run of ethernet twisted pair becomes one side of a capacitor, the other side being the building wiring, piping, or structure. The long run of telephone wire picks up static charge from wind, lightning ground currents, test currents from the telephone exchange or line workers, or induced currents from other subscribers or power network switching. Even turning on many lights. http://www.pololu.com/docs/0J16/all can give you an idea of what can happen. Any of these events will induce a starting pulse of DC in the telephone wire, which is analogous to the length of DC power cable in the Pololu explanation; the inductor. The low equivalent series resistance (ESR) capacitor can be thought of as the long cabling against the building. As a result of the capacitor and the inductor, the voltage is amplified until it reaches the breakdown voltage of whatever is connected. Having the UPS plugged in might have prevented this voltage from finding a route through something more precious. Instead, it might have found a route through a series of surge protection devices in the UPS, and then the only damaged equipment would be the ADSL modem. The convention is to build from the ground up. Don't plug the cables in until the ground is available, and then plug them in in strict order. People get away with not doing this because the damaging pulse isn't constant. (Reminds me of the time that I pulled a UPS input power plug out instead of just turning it off. A bad idea. The last pin to separate was active. The connected equipment lost ground reference, the only ground reference that remained was through a device, so it took a full hit and died. The resulting current passed into the building ground, and triggered the earth leakage breaker on the circuit that the UPS was originally connected to. Other equipment connected to that circuit powered down.) (Reminds me also of working for a cable contractor in the 1980s, looking after their cable management system on a VAX ... they were putting millions of cables into a power station, and the build was done from the ground up; that is cables were tracked as to whether they had been terminated yet, and the list of unterminated cables was a special report from the database that they always wanted to see.) I have seen that some UPSs (unfortunately not these ones) allow a phone line to be passed through them, supposedly offering some protection. Would such a system protect against a lightening bolt, assuming thats what happened here? Yes, but only if the UPS was earthed. It would also protect the ADSL modem. It would also protect from most other causes of a current pulse arriving on the phone line. -- James Cameron http://quozl.linux.org.au/ ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
Re: [Server-devel] School networks and electrical equipment damage
On Jun 6, 2013, at 3:58 PM, Daniel Drake wrote: Those of us familiar with setting up school networks (server + switch + APs) in some of our deployments will be familiar with the occasional loss of hardware, due to surges in the low quality electrical supply or whatever, even when the system is protected by a cheap UPS which supposedly offers some protection. This has often been the case in Nicaragua, so the group is now buying more expensive UPSes, PoE switches, and PoE access points for new schools. This means that the server and switch are connected to mains power via a UPS which hopefully protects them, and none of the APs are connected directly to the mains (instead they get Power over Ethernet) which hopefully offers some isolation from bad electrical conditions. This equipment is expensive, especially in places like Nicaragua where lots of import taxes are applied. But the hope is that the investment pays off in that the equipment doesn't get zapped. However, one week after deploying this equipment in the first school, we are left with a server that doesn't boot, 3 out of 4 access points broken with a nice burning electronics smell, and a broken switch with a lot of visible damage to the electronics. And the most surprising thing - we had not even turned on the network yet, pending some electrical work. Everything was connected up except one crucial link - the UPS was not plugged into mains power. So all of this damage happened without any of the devices having a connection to the mains. Connectivity-wise, the setup was: WAN: Phone line - ADSL modem - XS LAN: XS - Switch - 4 APs And power connections: the XS, ADSL modem and switch were connected to the UPS. The APs were connected to the switch over ethernet for both power and data. Again, since the battery was not connected to mains power, none of the devices had a power source. The connectivity engineer's best bet is that a lightening bolt landed at the school or nearby, and that this caused a power surge on the phone line. This surge passed through the ADSL modem, server, switch, and 4 APs, destroying everything in its path (except 1 AP that was connected over a longer cable than the rest). This was my most likely hypothesis as well. I believe the damage would have been less had the UPS actually been plugged in, but most probably have their input protected, not their outputs! I figured this is a story worth sharing, for any other projects considering splashing out on more expensive equipment... Also, I'm wondering if anyone has any advice/experience here. Would others expect this more expensive setup to be more resilient to bad electrical conditions than a cheaper setup - will the investment pay off? Cat5 Ethernet transformers generally provide 1.5 kV of isolation (at each end) but PoE breaks that. I believe the actual protection provided by the UPS can vary widely. They are usually required in situations like yours to protect the hard drivers, not as much for power line protection. I would use a periodically replaced surge protector before it and maybe a surge protected power strip after it. I figure that the case of a lightening bolt might be a bit extreme, but electrical storms are a nightly occurance here almost daily during the 6 month rainy season. Nothing will protect against a direct lightning strike of the wire. The more common case is a strike near the wire or the central office which can induce still induce many kV of surge on the lines. If electrical storms are common you need to take precautions. I hope all the network cabling is indoors ? If it is only partially so, consider something like: http://www.l-com.com/surge-protector-indoor-4-port-med-power-10-100-base-t-cat5-lightning-surge-protector I have seen that some UPSs (unfortunately not these ones) allow a phone line to be passed through them, supposedly offering some protection. Would such a system protect against a lightening bolt, assuming thats what happened here? Probably not. Primary protection on the phone line should be an gapped carbon block or gas tube protector at the entrance to the building between each line of the phone pair and a good ground.These protect against higher energy surges, and generally kick in at over 1 kV. I would suggest using primary protection that includes secondary protection, such as you see in: http://www.l-com.com/surge-protector-outdoor-high-power-telephone-dsl-lightning-surge-protector-screw-terminals You could also loop it through the UPS at this point for redundancy (but it MUST remain plugged in to provide protection --- it not, it makes things worse!) Then there is the protection in the modem itself, which should be able to handle the remaining surge. They are so common in telephony as to be required --- but primary protection and proper grounding is always assumed. Sorry to hear about your misfortunes, wad
Re: [Server-devel] [support-gang] ANNOUNCEMENT XSCE 0.3 Final Release
Good news indeed and my appreciation to all the hard work the XSCE team have put into. I recently installed R2 on SD a card for XO 1.75 (512 Mib) with 3 APs. It seems to be working fine with 30 XO-1s connected via different AP. Registration went well, ejabberdctl displayed registered users, moodle work, backup work. So I am a happy end-user waiting to see it deployed in the wild soon! T.K. Kang -Original Message- From: George Hunt [mailto:georgejh...@gmail.com] Sent: Friday, June 7, 2013 08:07 AM To: 'Community Support Volunteers -- who help respond to help AT laptop.org' Cc: 'Support Gangsters', 'server-devel', 'Testing', 'IAEP SugarLabs', de...@laptop.org Subject: [support-gang] ANNOUNCEMENT XSCE 0.3 Final Release After three months of hard work and three weeks of working out the kinks in the release process, XSCE 0.3 is ready for its final release. We went conservative this release. Emphasis on stability meant less time for new features. * XSCE now runs on the XO-1.5,XO-1.75 and XO-4. * Modular Architecture: cleanly integrate extendable services. * XSCE runs on the XOs' current OS 13.1.0 (we discovered some wrinkles with 13.2.0 which push its use off to the next release) * Moodle is Back! * Content filtering via openDNS.com * Script for formatting of SD cards, and integration into system for content storage and memory extending swap file (does not work on XO4's) Grab an XO-1.5, XO-1.75 or a XO-4 to give XSCE 0.3 give a whirl: http://schoolserver.org/0.3 If you are just getting started with XSCE we suggest using the instruction at http://wiki.laptop.org/go/User:Holt/XS_Community_Edition/0.3/Installingto install your first server. Once you are through the install, a good second step is to work your new server though it’s paces by doing the smoke test at http://wiki.laptop.org/go/User:Holt/XS_Community_Edition/0.3/Testing Monster thanks to everyone who spent months of springtime work -- traveling days from quite different parts of North America to make this community product real. George Hunt ___ support-gang mailing list support-g...@lists.laptop.org http://lists.laptop.org/listinfo/support-gang ___ Server-devel mailing list Server-devel@lists.laptop.org http://lists.laptop.org/listinfo/server-devel
