OpenSSH: Environmental Override November 1, 2008
Posted by Garrison in Case Study, HowTo, Linux.Tags: OpenSSH
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prerequisite concepts: prelude, basic configuration
This post is as much about customizing the root shell as it is about SSH environment variables, but I’m adding this to my OpenSSH collection because it’s applicable to 
any user.
I occasionally work on servers where, for a variety of reasons, I share an account with one or more other users; this is almost always suboptimal, but it does happen nonetheless. Over time I’ve grown somewhat partial to zShell, so one method I’ve used is to log in to a default shell, usually bash, then run zsh. (more…)
I have seen the light. October 4, 2008
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Having discovered the advantages of á la carte VoIP pricing, I pondered how to extrapolate my experience for general discussion while avoiding the pitfalls of interpolation and abridgement.
The Reference Book of Rates, Price Indices, and Household Expenditures for Telephone Service published by the FCC’s Wireline Competition Bureau provides a rough estimate of wireline telephone expenses averaging $45 per month in 2007, based on market research by TNS Telecoms. This isn’t too far from my own experience with residential VoIP plans which have tended to average about $35 monthly, including additional fees and charges, which can be significant: on BroadVoice’s “Unlimited World” plan, for example, “Taxes & Surcharges” account for about 35% of the monthly total. Based on these data, I use an estimated $35-$45 for generic comparison of monthly residential phone bills, or an average average of $40. As I designed our current, á la carte plan, I surmised that after discounting business use, the residential remainder was unlikely to ever exceed $30 in a single month. As the plan took shape, however, I realized that intelligent planning could lower that even further; somewhere in the neighborhood of a $20 monthly average would certainly exemplify what custom VoIP plans can offer, and half the average isn’t a bad talking point. 
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Doctor, I’ve got audit complaints about my kernel log. September 24, 2008
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AppArmor, introduced to Ubuntu with Gutsy, is yet another security tool unleashed upon the infosphere. In part, AppArmor is intended as an alternative to SELinux, which can easily be seen as daunting to configure; unfortunately, many such projects are daunting for those admins forced to walk the plank of unfamiliarity above a sea of expectations. Despite a troubled history, the project seems to be here to stay so it is likely only a matter of time before audit messages crop up in one’s kernel log. For those who find AppArmor unnecessary, unpalatable, or just untimely, herein lies a quick-and-dirty guide for telling AppArmor where to stick its audit complaints. (more…)
Three Things to Avoid in a VoIP Provider September 19, 2008
Posted by Garrison in Case Study, Linux, Reviews, Telephony.2 comments
Like many others, when I set up my first Linux PBX I knew little about VoIP providers and with few sources of reliable, current information, I made a decision based on name recognition, perceived value, and minimal research. Like many others, I looked for companies who advertised a BYOD plan under the false assumption that said companies would have a clue regarding said devices, despite the cautionary warnings which politely explained that BYO, as used here, means “unsupported”. Like many others, I signed up with BroadVoice believing I had a pretty good deal; in fact, among similar plans offered by cable companies and Vonage, BroadVoice compares rather well.
By the time I started to suspect BroadVoice of stockpiling probiscus laden mammals and bleach, I had already paid setup fees and number transfer fees, and chagrined the thought of early termination fees, more number transfer fees, and a potential three to seven week transfer period. Rather than add to the copious corpus of BroadVoice complaints, I thought I’d focus on what to avoid when choosing a VoIP provider. (more…)
When in doubt, test. January 14, 2008
Posted by Garrison in Case Study, Command Line, Debian, HowTo, Linux, Ubuntu.1 comment so far
Shortly after I last upgraded my mail server, one user reported that his mail client was failing to connect with the message:
"Unable to connect to your IMAP server. You may have exceeded the maximum number of connections to this server..."
He was the only one known to be having this issue, so after a cursory check of the server with no obvious problems, I suggested that this might be an error on his end, such as connecting to the secure IMAP port without using SSL/TLS. Occam’s Razor suggests that a server error is more likely than a client error which just happens to coincide with a server upgrade, so I eventually decided to dig up some infrequently used commands and perform a thorough analysis. (more…)
Quick and Easy Caller ID on MythTV December 31, 2007
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I have resisted the urge to display caller id on my MythTV 
as somewhat obvious. I’m always looking for ways to demonstrate the freedom which comes from using open source software, but I prefer the zesty freshness of an original idea rather than anything that’s been done, redone, and done again. My wife, however, thought that Myth caller id sounded like a great idea and asked me to set it up. What follows is how I did this with the least possible effort. (more…)
Quick Fix for Asterisk/BroadVoice Number Conflict. October 15, 2007
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I have a strange issue on my Asterisk box. If I call BroadVoice tech support using one of their trunks, I connect normally and hear the initial IVR, I press “1″ and hear “Your call is being transferred.” Then the weirdness starts: I remain connected, but I hear my own hold music. As near as I can figure, while I’m on hold in their call queue, Asterisk has dumped me in to hold and I can’t get out. If I stay on long enough for a tech to pick up, they either hear nothing or my hold music and hang up. Free beer goes to anyone who can identify and solve this issue, meanwhile I have developed a workaround. (more…)
Linux Bane October 15, 2007
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While I was cooking last night’s dinner, I made the mistake of leaving my laptop running, open, and unattended. Because ours is primarily a Linux household (my wife is a Mac user), 
I normally don’t worry much about the computers. The servers, devices, and desktops tend to chug along without needing anything more than an occasional `aptitude update && aptitude upgrade`. Laptops, however, are an entirely different story. As you can see in the photo, we live with a creature that is essentially a heat seeking missle bent on killing laptop computers. Sure it was funny the first couple times, but amusement quickly turned to horror when I saw that she can actually crash Linux. All my base are belong to her.
Red Box October 6, 2007
Posted by Garrison in Case Study, Essays, Linux, Telephony.6 comments
I finally built a red box, not the phone phreak device that generates coin tones for pay phones, but rather a Linux PBX which gives me the power and flexibility of a commercial grade phone system at a fraction of the cost. I call it a red box because the primary VoIP number I chose suggests [1]June 20, 1963– the day the “red telephone” went live between Washington and Moscow. Once I painted the side panels a nice, shiny red, I decided that in keeping with the metallic network naming I use (cobalt, tungsten, strontium, etc.) the best name for my new PBX would be ‘copper’. (more…)
Multiple Recipient Delimiters in Postfix August 29, 2007
Posted by Garrison in Case Study, Command Line, Debian, HowTo, Linux, Ubuntu.4 comments
Some time ago I enabled recipient delimiters (e.g. user+foo@host.tld) as a convenient way to know if shady web forms are 
contributing to my spam folder. The idea is that when House Depot requires me to have an account before I can see if they have loose screws in stock locally, I can sign up with garrison+housedepot@codefix.net instead of my usual e-mail. With recipient delimiters enabled, postfix will try to deliver any incoming mail to garrison+housedepot but when it finds no such user, it will try garrison and I get my mail. The problem arises when I discover that House Depot’s broken web form rejects any e-mail addresses with “+” in the user name as invalid. I’m already using garrison+foo style addresses elsewhere so I don’t want to change the recipient delimiter, but neither do I trust my real address to a company that can’t even create a proper web form. (more…)
