Search Results: "spa"

28 June 2008

Biella Coleman: On Anthropology, Participant Observation, and Non-Places

When you are in a foreign city, Dakar, Tunis, Tokyo, the spaces and sights are disorienting for they unfamiliar. But there are a few spots (hotels, supermarkets), that bring you back the familiar and these places have been theorized by French Anthropologist Marc Auge as non-spaces. Here is a nice interview with Auge on the difference between ethnology, anthropology, as well as his description of non-places:
I tried to characterize these new emerging spaces by the term non-places which empirically makes note of the extension of these new spaces in our world; spaces of circulation giving us the sense that the earth is small, spaces of communication (possibly virtual spaces), or even of consumption, since a large part of what circulates aims to put products into circulation (and possibly the men who produce them) such that the activity of consumption reproduces society itself. Such spaces of circulation, of communication and consumption, including the technical capabilities that make it possible for them to be visited or concentrated (the airport, the supermarket, the freeway, etc.), are what I have designated by the term non-place .

27 June 2008

Miriam Ruiz: Glass Ceiling

Katherine Lawrence and Marianne Schreiber, two women at Hewlett-Packard, used the term Glass Ceiling to to refer to invisible barriers that impede the career advancement of females. While on the surface there seems to be a clear path of promotion, in fact women seem to hit a point where there is no way to progress beyond. Carol Hymowitz and Timothy Schellhardt used the term again afterwards in the March 24, 1986 edition of the Wall Street Journal, which is considered by many people the starting point of the usage of that term. Even though the term Glass Ceiling was originally specifically applied to discrimination against women, its meaning has expanded to describe similar situations of other collectives. I was wondering whether there might be a Glass Ceiling in Debian too. I know some of you will be tempted to answer “no way!” or “yeah! of course!” without even thinking about it. Please don’t. Keep in mind that a Glass Ceiling situation is referred to as a “ceiling” as there is a limitation blocking upward advancement, and “glass” (transparent) because the limitation is not immediately apparent and is normally an unwritten and unofficial policy. Give a serious and deep thought about it before commenting. It’s quite likely that if you are too sure about what the answer might be, one way or the other, that you might be wrong. I just wanted to make us think a bit about it.

Russell Coker: The New DNS Mess

The Age has an interesting article about proposed DNS changes [1]. Apparently ICANN is going to sell top level DNS names and a prediction has been made that they will cost more than $100,000 each. A suggestion for a potential use of this would be to have cities as top level names (a .paris TLD was given as an example). The problem with this is that they are not unique. Countries that were colonised in recent times (such as the US and Australia) have many names copied from Europe. It will be interesting to see how they plan to determine which of the cities registers names, for the .paris example I’m sure that the council of Paris Illinois [2] would love to register it. Does the oldest city win an international trademark dispute over a TLD? The current situation is that French law unambiguously determines who gets to register paris.fr and someone who sees the URL will have no confusion as to what it means (providing that they know that fr is the ISO country code for France). As well as city names there are region names which are used for products. Australian vineyards produce a lot of sparkling wine that they like to call Champagne and a lot of fortified wine that they like to call Port. There are ongoing battles about how these names can be used and it seems likely to me that the Australian wine industry will change to other terms. But in the mean-time it would be interesting if .champagne and .port were registered by Australian companies. The fuss that would surely cause would probably give enough free publicity to the Australian wine industry to justify an investment of $200,000 on TLDs. The concern that is cited by business people (including the client who forwarded me the URL and requested my comments) is that of the expense of protecting a brand. Currently if you have a company named “Example” you can register example.com, example.net, and example.org if you are feeling enthusiastic. Then if you have a significant presence in any country you could register your name in the DNS hierarchy for that country (large companies try to register their name in every country - for a multinational registering ~200 domains is not really difficult or expensive). But if anyone can create a new TLD (and therefore if new ones are liable to be created at any time) it becomes much more difficult. For example if a new TLD was created every day then a multi-national corporation would need to assign an employee to work full-time on investigating the new TLDs and deciding which ones to use. A small company that has an international presence (IE an Internet company) would just lose a significant amount of control over their name. I don’t believe that this is as much of a concern as some people (such as my client) do. Currently I could register a phone line with a listed name indicating that it belongs to the Melbourne branch of a multi-national corporation. I don’t expect that Telstra would stop me, but the benefit from doing this would be minimal (probably someone who attempted fraud using such means would not gain much and would get shut down quickly). I don’t think that a DNS name registered under a .melbourne TLD would cause much more harm than a phone number listed in the Melbourne phone book. Incidentally for readers from the US, I’m thinking of Melbourne in Australia not a city of the same name in the US - yet another example of a name conflict. Now I believe that it would be better if small companies didn’t use .com domains. The use of country specific names relevant to where they work are more appropriate and technically easier to implement. I don’t regret registering coker.com.au instead of some name in another country or in the .com hierarchy. Things would probably be working better right now if a .com domain name had always cost $100,000 and there were only a few dozen companies that had registered them. But we have to go with the flow sometimes, so I have registered RussellCoker.com. Now when considering the merit of an idea we should consider who benefits and who (if anyone) loses. Ideally we would choose options that provide benefits for many people and losses for few (or none). In this case it seems that the suggested changes would be a loss for corporations that want to protect their brand, a loss for end-users who just want to find something without confusion, and provide more benefits for domain-squatters than anyone else. Maybe I should register icann.port and icann.champagne if those TLDs are registered in Australia and impersonate ICANN. ;)

Share This

26 June 2008

DebConf team: Talks for DebianDay wanted (Posted by Margarita Manterola)

This year, DebianDay will take place in Buenos Aires, on Monday August 18th, the day after DebConf ends. We are still in need of talks for DebianDay, so, if you are coming to DebConf and you’ll be staying a few more days in Argentina after the conference, you are invited to give a talk on whatever you want as long as it’s Debian related. Some suggestions for talk subjects for DebianDay: We are planning on having two tracks, one for newbies and one for advanced talks; talks in Spanish are welcome, but don’t worry if you don’t speak the language, for talks in English, we will probably have a translator. To submit a talk, just log in to your DebConf account and click in the “New event/Paper” link.

Decklin Foster: The data are

So I always knew that my ThinkPad's display sucked. But now I have scientific proof! (Long-winded post about my job follows.) I was running some timing tests at work on the code for a psychology experiment. This involves quickly presenting a stimulus to the subject, then measuring reaction time and synchronizing with EEG readings. Nothing very complicated, but accurate timing is essential; you don't want another variable confounding your results. So I have this photocell device that sends a signal to a Mac through the EEG hardware when there is really actually physical light coming off of the screen, not just when I told the computer to display something. Now CRTs, of course, are actually scanning (with an electron gun) the display at 75 or 85 Hz or something, not constantly pumping out light to the whole screen. This means 12 or 13 (or whatever) ms between refreshes. So if you want something to appear for 100 ms, you have to fudge a little, and make it so that you get maybe 8 or 9 scans. You can synchronize your presentation to the refresh so this is feasible. But how long the subject really perceives it ultimately depends on how "flickery" the monitor is at a given refresh rate. LCDs, on the other hand, do not have this problem. They actually do produce light constantly -- their refresh rate is pretty much always only 60 Hz or less, but you get the same(ish) output over the entire cycle, instead of in blips that give the illusion of a constant image (in fact, as Matthew points out, they can continue to hold the same image for even longer periods between refreshes. Can't wait to try out that patch). And luckily for us, 6 cycles are in theory exactly 100 ms (in practice, it's close enough). Or so I thought. I could not, no matter how many times I banged my head against it, get consistent results between our laptop (also a ThinkPad) and any external display. For reasons I do not entirely understand (probably scheduling issues), on CRTs I was getting one extra cycle, so I had to reduce the time by one to compensate. This was done for published studies years before I arrived at the lab, so (for the sake of not introducing additional variables) there is an extremely large disincentive to go back and fix it the Right Way, whatever that is. Our laptop's internal display was producing results that were skewed like those of a CRT. I thought for a minute I was going nuts from testing all day, but it kept happening. Curious, I swapped out the lab's T60 for my faster T61 and (to rule anything else out) killed all my other processes and wrote a fresh PyEPL script that did nothing but repeatedly blink some text for 100 ms. Here is, on the external VGA port, a cheap old 15" Dell LCD I pulled from the server room: http://www.rupamsunyata.org/~decklin/blogfiles/20080626/vga-lcd.png (These images are from the Mac, which is still using System 9.something. I had to remember Command-Shift-3 to take a screenshot and use StuffIt to get them off of it. Srsly. I can't remember the last time I used StuffIt.) And here is a CRT, showing the refreshes: (The DIN3 line is the actual signal, and the others are integrated over some number of milliseconds to compensate for scanning and attempt to get a usable number. Of course, this is done in hardware, not synchronized to anything else.) http://www.rupamsunyata.org/~decklin/blogfiles/20080626/vga-crt.png Now, this is the one that blew my mind. The ThinkPad's internal LCD: http://www.rupamsunyata.org/~decklin/blogfiles/20080626/lvds-lcd.png You can see that 60 Hz is spaced much farther apart, and that there are 6 cycles as intended, but. It's acting like a CRT! On the refresh, it puts out enough light to trigger the photocell, but inbetween, nothing. I ought to be noticing flicker and/or getting headaches all the time, if this is truly the case. (I guess I did get glasses for and because of staring at computer displays all the time. Should update my hackergotchi.) I have to admit I do not understand what is going on here at all. But it seems like making any assumptions about a display is (as the voice in my head was telling me all along) a very bad idea. Perhaps someone can email me some clue. But at least I have some hard data to validate my subjective opinion of the ThinkPad's internal LCD. Anyway: I still recommend the ThinkPad, even if the display is awful. I have a nice external monitor connected through DVI to the dock at home, and I mainly use a laptop so I can get out of the house and go hack outside or in a coffeeshop (not ideal lighting). The build quality, keyboard/trackpoint, performance, and the fact that Debian (testing or unstable, anyway) Just Works are all higher up on the list for me. I do wish I could afford the new lighter one, though.

Russell Coker: Kernel Security vs Uptime

For best system security you want to apply kernel security patches ASAP. For an attacker gaining root access to a machine is often a two step process, the first step is to exploit a weakness in a non-root daemon or take over a user account, the second step is to compromise the kernel to gain root access. So even if a machine is not used for providing public shell access or any other task which involves giving user access to potential hostile people, having the kernel be secure is an important part of system security. One thing that gets little consideration is the overall effect of applying security updates on overall uptime. Over the last year there have been 14 security related updates (I count a silent data loss along with security issues) to the main Debian Etch kernel package. Of those 14, it seems that if you don’t use DCCP, NAT for CIFS or SNMP, IA64, the dialout group, then you will only need to patch for issues 2, 3 (for SMP machines), 4, 5, 7 (sound drivers get loaded on all machines by default), 9, 10, 11, 12, 13, and 14. This means 11 reboots a year for SMP machines and 10 a year for uni-processor machines. If a reboot takes three minutes (which is an optimistic assumption) then that would be 30 or 33 minutes of downtime a year due to kernel upgrades. In terms of uptime we talk about the number of “nines”, where the ideal is generally regarded as “five nines” or 99.999% uptime. 33 minutes of downtime a year for kernel upgrades means that you get 99.993% uptime (which is “four nines”). If a reboot takes six minutes (which is not uncommon for servers) then it’s 99.987% uptime (”thee nines”). While it doesn’t seem likely to affect the number of “nines” you get, not using SMP has the potential to avoid future security issues. So it seems that when using a Xen (or other virtualisation technology) assigning only one CPU to the DomUs that don’t need any more could improve uptime for them. For Xen Dom0’s which don’t have local users or daemons, don’t use DCCP, NAT for CIFS or SNMP, wireless, CIFS, JFFS2, PPPoE, bluetooth, H.323 or SCTP connection tracking, then only issue 11 applies. However for “five nines” you need to have 5 minutes of downtime a year or less. It seems unlikely that a busy Xen server can be rebooted in 5 minutes as all the DomUs need to have their memory saved to disk (writing out the data to disk and reading it back in after a reboot will probably take at least a couple of minutes) or they need to be shutdown and booted again after the Dom0 is rebooted (which is a good procedure if the security fix affects both Dom0 and DomU use), and such shutdowns and reboots of DomU’s will take a lot of time. Based on the past year, it seems that a system running as a basic server might get “four nines” if configured for a fast boot (it’s surprising that no-one seems to be talking about recent improvements to the speed of booting as high-availability features) and if the boot is slower then you are looking at “three nines”. For a Xen server unless you have some sort of cluster it seems that “five nines” is unattainable due to reboot times if there is one issue a year, but “four nines” should be easy to get. Now while the 14 issues over the last year for the kernel seems likely to be a pattern that will continue, the one issue which affects Xen may not be representative (small numbers are not statistically significant). I feel confident in predicting a need for between 5 and 20 kernel updates next year due to kernel security issues, but I would not be prepared to bet on whether the number of issues affecting Xen will be 0, 1, or 4 (it seems unlikely that there would be 5 or more). I will write a future post about some strategies for mitigating these issues. Here is my summary of the Debian kernel linux-image-2.6.18-6-686 (Etch kernel) security updates according to it’s changelog, they are not in chronological order, it’s the order of the changelog file:


  1. 05 Jun 2008: CVE-2008-2358 for DCCP and CVE-2008-1673 for ASN.1 (NAT for CIFS and SNMP).

  2. 23 May 2008: CVE-2008-2136 memory leak in IPv6 over IPv4 tunnels, CVE-2007-6712 timer related bugs, CVE-2008-1615 ptrace on AMD64 architecture, and CVE-2008-2137 “Validate address ranges regardless of MAP_FIXED”.

  3. 07 May 2008: CVE-2008-1669 SMP race

  4. 11 Apr 2008: CVE-2007-6694 PPC only, CVE-2008-0007 Add VM_DONTEXPAND to vm_flags in drivers that register a fault handler but do not bounds check the offset argument, CVE-2008-1294 prevent user escape from RLIMIT_CPU, and CVE-2008-1375 fix dnotify race.

  5. 10 Feb 2008: CVE-2008-0010 and CVE-2008-0600 Fix missing access check in vmsplice.

  6. 25 Jan 2008: Not a security issue, but silent data loss on IA64.

  7. 22 Jan 2008: CVE-2007-6151 ISDN memory overrun, CVE-2008-0001 something related to checking the access to a directory, CVE-2007-2878 FAT filesystem related, CVE-2007-4571 ALSA bug that allows user to read kernel memory.

  8. 17 Sep 2007: Fix minor DOS attack for slightly privileged users (EG members of dialout group).

  9. 18 Dec 2007: CVE-2007-6063 overflows in ISDN subsystem, CVE-2007-6206 core dumping over an existing file can get the wrong ownership (should be possible to use kernel.core_pattern to work around this [1]), CVE-2007-5966 timer issue, CVE-2006-6058 Minix fs DOS attack via corrupted fs, and CVE-2007-6417 tmpfs memory leak.

  10. 29 Nov 2007: CVE-2007-3104 local kernel DOS attack (Oops), CVE-2007-4997 malicious frame on wireless interface crashes system, CVE-2007-5500 potential system hang, and CVE-2007-5904 CIFS overflows from server sending corrupt data.

  11. 02 Oct 2007: CVE-2007-4573 Xen 64bit with 32bit DomU, CVE-2006-5755 Xen, CVE-2007-4133 memory management DOS, and CVE-2007-5093 DOS when unplugging a webcam that is in use.

  12. 25 Sep 2007: CVE-2007-3731 ptrace causing Oops, CVE-2007-3739 memory management Oops, CVE-2007-3740 CIFS not honoring umask, CVE-2007-4573 ptrace of 32bit process on AMD64 bug, and CVE-2007-4849 JFFS2 (flash media) filesystem bug.

  13. 27 Aug 2007: CVE-2007-2172 IPv4 memory related issue (local DOS or compromise?), CVE-2007-2875 local user can read kernel memory if cpuset filesystem is mounted, CVE-2007-3105 buffer overflow in random number generator, CVE-2007-3843 CIFS, and CVE-2007-4308 AAC RAID.

  14. 11 Aug 2007: CVE-2007-1353 bluetooth, CVE-2007-3513 usblcd, CVE-2007-2525 PPPoE, CVE-2007-3642 H.323 connection tracking, CVE-2007-2172 IPv4 local exploit, CVE-2007-2453 slightly less random numbers, CVE-2007-2876 SCTP connection tracking, CVE-2007-3851 i965 batch buffer usage, and CVE-2007-3848 potential privilege escalation.

Share This

Uwe Hermann: Configure Firefox/Iceweasel 3 to be more secure / usable / bearable

Today seems to be Firefox/Iceweasel 3 Bashing Day on Planet Debian, so let me join the fun :) I agree with most other people that the default Firefox/Iceweasel 3 config is not ideal, so here's what I did to fix it. Some of these items improve performance, some remove annoyances, some remove privacy issues, some remove security issues. Not everything here may be desirable for people other than me. General Preferences Select "Edit / Preferences". Main: Tabs: Content: Privacy: Security: Advanced:

Edd Dumbill: My OSCON 2008 picks

In just under a month, the tenth O'Reilly Open Source Convention will get underway in Portland. Over ten years OSCON has developed—along with the world of open source—into an intense, exciting, informative, diverse and exhausting event. This year I've the privilege of being co-chair, along with Alison Randall. We've packed so much into the show, it's a difficult job even being able to comprehend it as a whole! Fortunately, there's a way to start making sense of things before you arrive there, thanks to the personal scheduler. Just mark the sessions you want to go to with a star, and you'll be able to plan out your time in advance. I wanted to list a few sessions from my own personal schedule that particularly piqued my interest. Then at the bottom of this post I'll share a discount code which can give readers of this blog 15% off OSCON registration. There's bribery for you. Practical Erlang Programming Largely thanks to XMPP enthusiasts and ejabberd, I've been hearing increasing amounts about Erlang, and I'd like to know enough about it to be dangerous. This three hour tutorial looks just the ticket. Open Source Virtualization Hacks This is one of several sessions we have on virtualization, something I'm particularly pleased about. Virtualization may be "done" at the kernel level, but I think we're only just starting out on its application. This session is by my friend and sometime co-author, Niel Bornstein, who works for Novell on just this sort of thing. Using Puppet: Real World Configuration Management Puppet is the piece of open source software that is most exciting to me at the moment. As a developer, it enables me to manage my machines like I'd manage my code libraries. A must-see if you've not used Puppet yet. These are just 3 out of the 300 or so confirmed sessions. Don't forget there's a large number of events and parties happening around OSCON too. And finally, the discount code. Use the code os08pgm when you're registering, and you'll get 15% off the ticket price. See you in Portland!Join the conversation about this post

Russell Coker: Dell PowerEdge T105

Today I received a Dell PowerEDGE T105 for use by a client. My client had some servers for development and testing hosted in a server room at significant expense. They also needed an offsite backup of critical data. So I suggested that they buy a cheap server-class machine, put it on a fast ADSL connection at their home, and use Xen DomU’s on that for development, testing, and backup. My client liked the concept but didn’t like the idea of having a server in his home. So I’m going to run the server from my home. I selected a Dell PowerEDGE tower system because it’s the cheapest server-class machine that can be purchased new. I have a slight preference for HP hardware but HP gear is probably more expensive and they are not a customer focussed company (they couldn’t even give me a price). So exactly a week after placing my order I received my shiny new Dell system, and it didn’t work. I booted a CentOS CD and ran “memtest” and the machine performed a hard reset. When it booted again it informed me that the event log had a message, and the message was “Uncorrectable ECC Error” with extra data of “DIMM 2,2“. While it sucks quite badly to receive a new machine that doesn’t work, that’s about the best result you can hope for when you have a serious error on the motherboard or the RAM. A machine without ECC memory would probably just randomly crash every so often and maybe lose data (see my previous post on the relative merits of ECC RAM and RAID [1]). So I phoned up Dell (it’s a pity that their “Packing Slip” was a low quality photocopy which didn’t allow me to read their phone number and that the shipping box also didn’t include the number so I had to look them up on the web) to get technical support. Once we had established that by removing the DIMMs and reinserting them I had proved that there was a hardware fault they agreed to send out a technician with a replacement motherboard and RAM. I’m now glad that I bought the RAM from Dell. Dell’s business model seems to revolve around low base prices for hardware and then extremely high prices for extras, for example Dell sells 1TB SATA disks for $818.40 while MSY [1] has them for $215 or $233 depending on brand. When I get the machine working I will buy two 1TB disks from MSY (or another company with similar prices). Not only does that save some money but it also means that I can get different brands of disk. I believe that having different brands of hard disk in a RAID-1 array will decrease the probability of having them both fail at the same time. One interesting thing about the PowerEdge T105 is that Dell will only sell two disks for it, but it has four SATA connectors on the motherboard, one is used for a SATA DVD player so it would be easy to support three disks. Four disks could be installed if a PCIe SATA controller was used (one in the space for a FDD and another in the space for a second CD/DVD drive), and if you were prepared to go without a CD/DVD drive then five internal disks could probably work. But without any special hardware the space for a second CD/DVD drive is just begging to be used for a third hard disk, most servers only use the primary CD/DVD drive for installing the OS and I expect that the demand for two CD/DVD drives in a server is extremely low. Personally I would prefer it if servers shipped with external USB DVD drives for installing the OS. Then when I install a server room I could leave one or two drives there in case a system recovery is needed and use the rest for desktop machines. One thing that they seem to have messed up is the lack of a filter for the air intake fan at the front of the case. The Opteron CPU has a fan that’s about 11cm wide which sucks in air from the front of the machine, in front of that fan there is a 4cm gap which would nicely fit a little sponge filter. Either they messed up the design or somehow my air filter got lost in transit. Incidentally if you want to buy from Dell in Australia then you need to configure your OS to not use ECN (Explicit Congestion Notification [2] as the Dell web servers used for sales rejects all connections from hosts with ECN enabled. It’s interesting that the web servers used for providing promotional information work fine with ECN and it’s only if you want to buy that it bites you. But in spite of these issues, I am still happy with Dell overall. Their machine was DOA, that happens sometimes and the next day service is good (NB I didn’t pay extra for better service). I expect that they will fix it tomorrow and I’ll buy more of their gear in future. Update: I forgot to mention that Dell shipped the machine with two power cables. While two power cables is a good thing for the more expensive servers that have redundant PSUs, for a machine with only one PSU it’s a bit of a waste. For some time I’ve been collecting computer power cables faster than I’ve been using them (due to machines dying and due to clients who want machines but already have spare power cables). So I’ve started giving them away at meetings of my local LUG. At the last meeting I gave away a bag of power cables and I plan to keep taking cables to the meetings until people stop accepting them.

Share This

25 June 2008

Pablo Lorenzzoni: Exciting new World

I ve just tested the improvements in the performance of Javascript in Firefox 3 and WOW! Javascript in FF3 is really fast. While googling about it I just ran across a recent interview with Brendan Eich about the future of Javascript and I got excited about two things about this future. First was what we already have, still in the beginning, but with a lot of potential: HotRuby. Really interesting to script a webpage in Ruby (which is my favorite language) and, while it s not embedded the way Javascript is, it gets compiled in the server side with YARV (the new bytecode compiler for the next version of Ruby, 1.9), and then served to the browser in the form of JSON objects, so it can be interpreted by the Javascript engine in it. All this is transparent and work with XMLHttpRequest. It s not a coincidence that Eich mentions it as being a form of ARAX (changing the J in AJAX for R from Ruby). I already do a lot of coding in Ruby not having to deal with Javascript anymore is surely a plus. ITOH, Eich is talking about improvements in Javascript that would render it as a real programming language Maybe coding in it would not be so painful anymore by then ;-) The whole interview have to do with this Project Tamarin, a high-performance, open source implementation of the ECMAScript 4th edition (ES4) language specification [ ECMAScript 4 is the same thing as Javascript 2 ] by the Mozilla developers. And this is the second thing I got excited for: they ve planned to glue IronRuby (Ruby compiler for argh! .NET) to it via IronMonkey. So exciting news! Either via Tamarin or via HotRuby, we ll get Ruby browser scripting. My free mind tends to favor HotRuby instead of IronRuby/IronMonkey/Tamarin But in the end what matters is that all those people now cursed by Javascript will finally have a taste of what a real programming language feels like.. Who knows! They might even like it ;-D

David Moreno Garza: YAPC::NA 2008

So I attended the conference last week in Chicago, IL. I was just been procrastinating to write about this.

As a (almost) complete outsider of the Perl community, I have countered thoughts about the whole event:

After all, it was quite a nice and new experience. I'm not totally sure I'll attend YAPC::NA 2009 in Pittsburgh, PA, we'll see.

Clint Adams: Relaxation

I was misled. That much is probably true. I certainly had no idea what I was getting myself into. Enough of that though; there's narrative fading away. The part I should take responsibility for is the decision I made to stray off the map. Perhaps it was not so much a decision as a compulsion. I looked at the map. I saw the suspicious unmarked area at the edge, and concluded immediately that there was something good there, something the people wanted to keep hidden from me. I was correct, but I presumed far too much about the terrain. I thought I would make a quick exploration of the secret place, then backtrack to the more mapped area and get back with the program. Enough of that though; I've nearly forgotten the story. First I should point out that, had the map been to scale, it should have taken me an leisurely fifteen minutes to get to my first destination. It should have, assuming the land would be as flat as the map that represented it. Instead, it turned out to be something one could cover in fifteen minutes if one had, say, a jetpack and spring boots. I'm probably wrong; I'd probably injure myself in the process and take longer. Anyway, the average incline was close to 45 , and luckily was mostly uphill. Luckily. When I got to a resting place, I was able to conclude that my supply of fluids was almost certainly insufficient for me to continue. On the other hand, there was probably no way I would return if I went back for more drink. I told myself that there would likely be a beverage-selling shack out in the middle of nowhere around the next bend or so. Having solved this probability problem, I pressed on into the blazing sun. I came to a path leading down to the sea. It was unclear what was down there, but it was clear that it seemed to be a million miles down, and that that path might be the only way back. Given my current state of exhaustion and hydration, I decided to pass on this opportunity. After continuing for a while, the features at the bottom of that path became visible. A very pretty cove was down there, and almost certainly no shack o' drinks. I then came upon a fork. A wide path led downward: to what, I could not see. To its left, a narrow and rough path led straight. Knowing that a descent probably meant climbing four to eight times the altitude back somehow, and assuming the less pleasant-looking path led somewhere better, I went left. After a while, the land began to slope down, ever so slightly. Little clusters of bottles and newspapers were left on the rocks here and there. Then came a sofa under a tent. I began to wonder what hippies were traveling this path. The slope grew greater, and I passed a bench in a tent. Then I came to a giant staircase, almost straight down. It was covered in weeds and insects. Some were vegan, some wanted my flesh. As I got toward the bottom I thought about how glad I was that I had come that way from the top and not the other way around. Oh, I was very glad. At the bottom was something resembling a plastic bottle graveyard and barrels among barrels filled with water. Rubber hoses seemed to run randomly between certain barrels. A kitchen stood at the edge of some barrels. I suddenly got the feeling that I was not supposed to be here. After discovering that a couple of escape routes were actually dead ends, I proceeded to descend a small staircase to a terraced garden. Hoses lay about the rows, presumably for watering the plants. A cot under a tent lay empty, and I hurried past hoping I would not encounter the owner. Then I was at the ocean. The coast was lined with huge boulders, and a wooden bridge led me to the first one, and another wooden bridge took me to the second. Then the bridges stopped. In the distance, I could see that pretty little cove from before. I took stock. I could either return whence I came, up that horrifying staircase, or I could try to traverse the rocky coast over to the cove, then maybe do a faceplant on the beach and let the tide drown me rather than climbing back up. It seemed like a no-brainer, so I began making my way toward the cove. It got harder. Several times I became very afraid, either of falling and smashing my head against a rock or falling into the water below, or some sequential combination thereof. In the end I turned out to be more afraid of going back, at least until I got to what I judged the point of no return. I was reasonably close to where I imagined the sandy beach started, but there was a huge and impassable boulder in the way. Also, if I went further there was no way I would be able to climb back up in case I needed to retreat. I was thinking I would need to retreat, because unless there was some magical hidden toehold, I would be forced to jump into the water and swim around. I did not want to jump into the water. I wanted my phone to stay unfried in the event that I would need to use it to get rescued. I also did not want to call anyone to get rescued, especially since I didn't really know how to explain where I was. With a heavy sigh, I gave up, turned, and went back. This time I moved more quickly, though incurring more damage to my hands and feet. No humans were visible at the crazy farm/garden and makeshift reservoir, but plenty of bugs were visible on the staircase. I made the mistake of trying to lean against the railing to catch my breath. When I finally got to the bench in the tent, I understood exactly what it was for. I sat down, took a sip of my remaining water, ate an apple, and kept going up. When I got to the couch, I sat again. This time I sat and tried to figure out a plan. I still clung to the belief that once I got back to somewhere less wild I'd be able to buy a drink. I noted that I only had a little bit of water left, that I was dehydrated, that I was sunburned, that my pulse was about 180, and that there were no dogs or Russian people wandering past me. I ate a pear and drank my last few drops of water. I kept sitting until my pulse was down to around 150, then I figured I needed to keep moving. I was experiencing most of the effects of caffeine, and for free. Oddly, I passed a dog a few steps later. It was just standing by a rock, looking at me. I decided not to converse. When I had nearly reached the fork again, a couple came my way. I thought about begging them for water. I decided not to be rude. I have no idea what happened to them. I'm betting they wisely decided not to go down the steps. Resolving that the only sane option was to go back all the way to where I absolutely knew I could buy something potable, I headed in that direction. Still, I took two risks. Instead of going up the exact way I had come, or taking a well-travelled path down, I took a narrow and flat dirt path. It was actually a bit of a dilemma. I started down the latter two more than once each. Finally I saw that the down path was rather V shaped, and I concluded correctly that the straight path would bypass that angular-half-pipe-like construct. When I finally got to a point I recognized, it was smooth sailing the rest of the way down. I bought water and a snack, since I had had almost nothing to eat that day. At this point it would have been prudent to call it quits and go off and gorge myself on seafood or something, but no, I was now in the mapped area and surely it would all be roses and manna. Finishing one bottle, I bought two more. Five minutes later I bought another. I had now overcompensated, but I was playing it safe. I continued my explorations. Bicyclists kept nearly running into me, and, aside from the obvious, I viewed this as a good sign. Bicyclists, especially those that can't seem to steer straight for some reason, avoid difficult terrain. This is why they take their bikes on subways, trains, and buses. I don't like bike-riding, but if I had my druthers, I would always go downhill. No up, no flat, just down. Like downhill skiing, just down. It is a good thing I don't ride a bike. Once I got to the point where the bicycles thinned out to nonexistence, I was at an intersection. The way I wanted to go was up. The way I didn't want to go, but was a reasonable option, was only very slightly up. Additional factors complicated this decision point. [elision] This passage has been marked friends-only and you will not be able to view it without logging in. Moving hurriedly away from there, I headed upward. After a couple of turns, I ran into Catholics. First there were dead Catholics. Then there were Catholics pre-occupied with dead Catholics. Then there were Catholics waiting to die. Then there were seminarians. Then there were teens with prayer books. When I reached the next pinnacle, there were more teens with prayer books. There were benches, and there were no teens on them, for the teens were standing or sitting on the ground, quietly contemplating the Word. Unfortunately, they had decided that the benches were more suitable for holding all their bags, so there was nowhere for me to sit. I considered interrupting their reverie, but decided it wouldn't be very Christian of me to disturb them, so I just placed an ancient Drasnian curse on them and plodded down the hill toward a small beach. I really didn't need any more sun, but at least there probably wouldn't be anyone praying there. The water was tempting, but I'm always paranoid about my belongings when swimming alone, and if my phone were taken I wouldn't be able to call anybody to come rescue me at the next crisis point, sure to come. So I skirted the coastline and arrived at a much larger beach, one with facilities and services. Opting to save money but complicate things by using the public changing rooms and showers, I made a discovery. [elision] This passage has been marked friends-only and you will not be able to view it without logging in. Nonetheless, I changed into my swimming trunks, stuffed everything else but my towel, sunglasses, and a disgusting sugary drink I never should have bought into my bag, and went barefoot a few buildings down to rent a locker. The locker was ridiculously large for a single person, which is good to know should I ever want to kidnap a family and torture them at this place. The proprietor informed me that they were closing at some specific time, about an hour from then. I had no timekeeping device outside of the locker, so I had to wing it, and erring heavily on the side of caution, I had a short beach diversion. Given that large swathes of my epidermis were turning bright red, it's probably for the best. Handling the shower, locker, and changing in the other direction was slightly more complicated, but I did it and then I headed inland, figuring I should have a substantial meal for once that day. On my way to find dinner is when things got really crazy. [elision] This passage has been marked friends-only and you will not be able to view it without logging in. I wandered over to a bench to eat my newly-acquired snack, and did not exercise enough caution, because the flimsy paper bag ripped and I got sauce all over my pants and a little on my shirt. Unfortunately I had used my napkin in that earlier episode, and I'm not sure how much it would have helped anyway. Thus I continued on, looking like a slobby retard. Then I made an obviously-poor decision and ended up having a subpar dinner. What happened after that is a story for another time.

Adrian von Bidder: Sometimes providers do get better...

Christian, I used to block quite aggressively (essentially blocking all IPs sending me spam for a few months) and remember seeing free.fr very, very often. Apparently this was before the block outgoing port 25 policy — I just had a grep through my log and see almost no spam coming in from free.fr. So, as I've said just recently, this is a note to all ISP: please, please, please block port 25! (ISP who don't offer unblocking will obviously lose the techie clients, but that's their own thing to decide...)

24 June 2008

William Pitcock: E-mail autoresponders suck. Please stop using them.

I find it particularly annoying, when I write a mail to a list, like say, the NANOG list, and get emails in reply like:
From: EMAIL ELIDED
To: William Pitcock <EMAIL ELIDED>
Subject: NAME ELIDED is out of the office.
Date: Tue, 24 Jun 2008 12:02:35 -0400 (11:02 CDT) I will be out of the office starting 06/23/2008 and will not return until 06/26/2008. If this matter is urgent please contact NAME ELIDED at XXX-XXX-XXXX or XXX-XXX-XXXX
This really sucks, for multiple reasons. Mostly, that: So please, for the good of all of the Internet, stop using autoresponders, because they are hideously lame. Or, at least, put something like AUTO-REPLY in your autoresponder so we can just delete the spam you insist on sending us. Thanks lazyweb.

Pablo Lorenzzoni: Ruby security advisory and fix

Debian 4.0 version of Ruby is open to the, now widely known, Ruby security vulnerabilities. The bug is reported as 487238 in Debian s BTS, and is closed, since the version now in sid (version 1.8.7.22-1) is already fixed. Users of stable can apply the patch provided by Daniel Franke (it doesn t seem to fix all, but goes a long way). Apparently, this brought up (again) the rants over full disclosure. Indeed, what is vulnerable is not that hard to find, as Zed Shaw showed us, so, why not talk about it in a plain and bold form? Why just provide the CVE numbers and ask for everybody to upgrade? Zed goes more deep about the quality of C code, but that is not the issue I want to talk about As a Free and Open Source Software supporter (and developer), I can see the benefits of full disclosure. As a not-full-time webmaster, I can see the benefits of not having a proof-of-concept piece of code attached to the vulnerability report. Of course, there s a lot of things a webmaster can do to prevent having a machine completely compromised in case a security advisory is published with a proof-of-concept code in it (think about chrooting, randomized memory protection, security libraries, grsecurity, SELinux, etc) and my machines, although vulnerable to the bug, would not be fully compromised if exploited. I guess one should be prepared to whatever comes from the Internet Full disclosure, in this sense, have more pros than cons, IMHO. For instance it was not clear if Debian 4.0 were vulnerable There were no security advisory coming from Debian (and there s still not), and it is not promptly obvious if the version packaged is affected. I know that at least I wanted to run a proof-of-concept to check if my server is vulnerable or not before going all the way into packaging a fix (or backporting the sid version), and it was not until I read Matasano Chargen Blog that I could test older versions. But different people have different ideas

Matthew Garrett: Power management design philosphy

One of the traditional problems with power management has been balancing power savings against reduced functionality. The two traditional approaches to this have been to have sane defaults or to let the user tweak them, with a hybrid approach being to have sane defaults and an "advanced" box that lets users set their own parameters.

Both of these options suck.

The problem with sane defaults is that power management is an area where the "sane default" genuinely does differ between users. Usage patterns will determine the appropriate spindown period for a hard drive. AHCI's ALPM will disable hotswap detection, which is fine for home users but a pain if people want to rip out a failed RAID element. ALPM also introduces a small amount of latency (on the order of a seek in the most aggressive mode), which is entirely irrelevant for almost everyone but is a pain if you're trying to offer i/o latency guarantees. PCI-E link power management adds small quantities of latency. Letting the CPU run to full speed whenever it wants to is good for power management but potentially bad for thermal management. Screensaver timeouts vary depending on whether you're watching a movie or not.

The problem with leaving everything tweakable is that you're asking users to make choices about things but not giving them the information they need to make those choices. Whether you get a power saving from hard drive spindown depends on whether the drive is idle for long enough to save the power you'll spend spinning it back up. Get it wrong and you'll be putting your drive under extra load, reducing performance and consuming more power than you were to begin with. If you limit the maximum speed of your CPU to keep it cool, you'll be wasting power and performance even when it's well below the thermal limits. Disabling ALPM because you might want to change a RAID device at some stage means you're consuming power despite generally not needing to use the additional functionality.

But while these options both suck in different ways, they share one fundamental failure. They both imply static configuration. The correct power management policy depends on the way that a machine is being used at a specific instant in time, and no matter how many power management profiles you add there's no way for a user to switch between them fast enough to obtain a decent power/performance ratio.

Adaptive power management adopts a different strategy. Rather than define a static policy (or several static policies), the hardware is monitored to determine the best power management settings. An example of this is the ondemand CPUfreq governor. Rather than attempt to provide a static configuration, the processor frequency is automatically changed to meet demand while also keeping the overall power consumption as low as possible. This patch adds a thermal component to its policy, preventing the machine from overheating. Result? No requirement to provide tunables to userspace.

Something similar is achievable with hard-drive spindown. By simply monitoring how often reads or writes actually hit disk, it's possible to automatically adjust the spindown period to obtain decent power savings while reducing the number of spinups. This approach is imperfect - in an ideal world we'd know to spin the drive up before it's needed, but that simply isn't possible. However, the user is almost certainly unable to make a better guess. It's not realistic for a user to be able to predict whether or not a given page is still in cache or has been evicted. Nothing is lost by providing a dynamic policy, and another unnecessary tunable has vanished.

The difficult part of an adaptive policy comes when roles are switched in ways that don't correspond to changse in hardware status. One of the most common cases is that of screensaver settings when the user is watching a video. It's not practical for the kernel or a system daemon to predict this case, so we have two choices:.One of these choices involves the user having to explicitly state something that's obvious - playing a video automatically implies the desire to adopt a different power management policy, and so asking the user to manually adjust that is ridiculous.

The loss of hotswap notifications when ALPM is enabled? Simply reenable it if SMART starts complaining or the RAID set becomes degraded or a filesystem is unmounted or any of the other things that will have to be done before a drive can be safely removed. Latency an issue? Let userspace tell you what its latency requirements are. When we get down to it, the only settings that we can't infer are things like idle-time-to-suspend, screensaver settings and default brightnesses. Which, curiously, are about the only things that Mac OS exposes[1].

The problem we face is that we don't currently have interfaces to let applications tell us what their requirements are. This is theoretically straightforward, but getting it right is important. Beyond latency and screensaver issues, what constraints do applications want to impose? How can we expose an interface to those constraints? This is the sort of thing we'll be looking at at the Linux Plumbers Conference, so if you have ideas about what they'd need to look like then sign up. Or, even better, submit a paper and be part of the process that gets Linux's power consumption as close to the theoretical minimum as possible.

[1] My Vista system gives me 25 options which can be set for each of AC and battery.

Ross Burton: Spawning Shells

As a followup to yesterday's post I profiled the speed of various ways of executing shell scripts on both my laptop using Bash and Dash, and on the Zoom OMAP3430 development board. The results are fairly predictable although the relatively small difference between . foo and ( . foo ) is useful to know. We all knew that Dash was faster than Bash, but this microbenchmark demonstrates it very clearly. It also demonstrates how much faster my laptop is than the (relatively powerful) Zoom development board. Overall conclusion: don't use Bash unless you needs the extra power, and source when possible. NP: Aerial, 2562

23 June 2008

Obey Arthur Liu: Daniel Burrows on cwidget-gtk

Sometimes people propose other solutions to have the Aptitude-gtk project done, like :
I d have thought that the most interesting way of doing aptitude-gtk would be to write a gtk backend for libcwidget. -Karellen
As this might be of interest to more people, I’ll repost Daniel Burrows‘ response :
Although I can see where you re coming from, a GTK+ backend to cwidget would have no significant upsides and significant downsides. The main upside to doing that from a practical point of view is that you would have only one piece of driver code for the GTK+ and curses interfaces. You wouldn t have to rewrite the entire interface from scratch to create a GUI frontend. But this is just an illusory benefit. cwidget is a terminal interface library and aptitude s curses frontend is a terminal-based UI. From a practical point of view, this means that aptitude regularly assumes that, for instance, to clear out a line it s sufficient to output $WIDTH space characters (ASCII 32) with the desired background style. A port of cwidget to GTK+ would have to introduce new, interface-independent abstractions for all operations like this and eliminate all direct use of terminal-based assumptions, at a significant cost in complexity for both cwidget and the aptitude frontend. In order to transition to these new conventions, I believe you would have to rewrite large portions of both cwidget *and* aptitude in order to make the interface abstraction layer work. (remember: the justification for doing this is to avoid having to rewrite aptitude!) Furthermore, while this approach avoids reimplementing aptitude s curses interface (sort of, except where it doesn t see above), it does so at the cost of requiring you to reimplement all of cwidget, for GTK+. I just did a quick line count (with wc -l ): in all of cwidget there are 23,390 lines of code, while aptitude s curses frontend has around 23,359 lines of code (some of which are actually shared with the other frontends but are in the curses directory due to the historical organization of the code tree). Not only is a rewrite of cwidget more involved, but the amount of code you d have to replace is comparable to the amount implicated in a rewrite of aptitude itself! Finally, even if these costs weren t enough to eliminate the idea, it s not at all clear to me that a GTK+ backend for cwidget is even desirable. Although aptitude has some superficial similarities to a GUI program, the process of designing an interface to run in a terminal (where the available input mechanisms are relatively restricted and all output is to a character-cell grid) is rather different from the process of designing a GUI. GUI programs can t rely on some simplifying assumptions that terminal programs can, and at the same time they have a lot more options available to them (just to name a few: graphics, multiple windows, differing text sizes and rotated text). Trying to force everything through an abstraction designed for terminal output would require you to either
  1. eschew those options,
  2. provide abstract GUI components that somehow fell back to terminal rendering in a terminal, or
  3. add ways for the frontend to extend the abstract widgets with custom functionality.
1. is not an option because I (and, I think, Arthur) want to design a good GTK+ package manager, not a good GTK+ imitation of a console package manager. 2. and 3. amount, in my strong opinion, to writing two separate interfaces but intertwining their implementations in a mass of maintenance-resistant and extension-resistant spaghetti code. At the end of the day, I think that having two separate frontends (sharing backend logic where appropriate, of course) is a far cleaner and more maintainable design, and also easier to create.
As I said earlier, I intend to go a little farther than just making a GTK+ “skin” over the curses interface. Think less like gvim and emacs and more like maybe ddd. I should also add that the cwidget library is used by no major programs except Aptitude so few others would benefit from a GTK+ backend. As the cwidget library homepage says:
cwidget was originally an internal user interface library for the aptitude package manager. This means, on the one hand, that cwidget is known to work in the real world for a real application; on the other hand, it means that the feature set of cwidget is coextensive with the requirements of aptitude.

Christian Perrier: On random blacklisting of mail servers

Yesterday, I again got a stupid thing like: 
: host YYYYYYYYYYY.de[AA.BB.CC.DDa] said: 550
    5.7.0 ... We don't accept mail from SPAM-friendly
    providers (in reply to RCPT TO command)
That's insane. Do people really want to communicate? This was about a bug in a Debian package and the above is the address used by the maintainer in his package. Dude, when you put your name in a package, please accept that people will want to send you mail and will want to be able to do so *easily*. The original mail was sent from my home server, hosted on a fixed IP address of the French ISP provider Free. The address has reverse DNS resolution and my system never sent spam or never was used to send spam. Free has a policy to block outboind port 25 for its customers unless they explicitely request to open it...which is IMHO the best compromise to avoid thousands of zombie Windows computers to send out spam. Blocking random blocks of IP addresses because they are "used by ISP customers" or because "one should us one's ISP mail server" is nonsense. This is not the Internet I knew and this is not the Internet I want. I don't see any reason why my home server would be worse than Free mail servers. I know what spam is. I receive tons of it and I had to take measures to limit and filter it. These measures never involved such stupid blocking by IP address and silly blacklisting. I use the Internet to communicate and I want people to be able to reach me, not going through weird ways to find their route to my precious mail address. That was the random rant of the day. I know many people will maybe comment on why Filtering Is Good or why I Shouldn't Be Sending Mail Directly But Use My ISP. Feel free to do so but also think about it: aren't we using mail to freely communicate? Blocking IP addresses randomly is just the poor man's solution to spam.

Russell Coker: TED - Defining Words

I recently joined the community based around the TED conference [1]. The TED conference is expensive ($6000US) and has a long waiting list (the 2009 conference is sold out) so it seems quite unlikely that I will ever attend one. But signing up to the web site is easy and might offer some benefit. One thing that interested me was that part of the sign-up process requests that you select up to 10 words from the list above to describe yourself. Some of the words seem almost mandatory for anyone who is interested in what TED has to offer (I find it difficult to imagine someone declaring that they are not an “activist” or a “change agent” while wanting to be involved with TED in any way). The range of words also seems quite strange, there are some professions mixed with educational status, marital status, and religion. The way it is laid out would tend to encourage people to make a decision as to which aspects of their life are more important, is career, marital status, or religion more important? Given the nature of TED I’m wondering whether the intentionally did a bad job of that part of the site design to encourage people to think about these issues. It seems to me that a better way of doing this would be to provide a few suggestions and allow people to fill in text fields with their own values. Even defining marital status can require many choices and there is no limit to the number of religions and careers. If you try to make a comprehensive list then you will end up doing what British Airways did with their frequent flyer membership application page [2]. Even disregarding the choices of spelling (EG Admiral vs Admiraal and Brig Gen vs Brig General vs Brigadier General) the British Airways list is unreasonably long, and I doubt that anyone who deserves the title “Her Magesty” or “His Holyness” is going to be interested in frequent flyer points. Also I wonder which of the entries in the TED list would be most commonly accepted by the free software community. It seems that activist and technologist would be quite popular. Here is the list in text form for those who can’t get the picture above:

Activist, Agnostic, Architect, Artist, Atheist, Athlete, Blogger, Brainstormer, Buddhist, Business adviser, Business leader, Business mentor, Care taker, Change Agent, Christian, Clergy, Concerned citizen, Connector, Consultant, Designer, Doctor, Educator/Teacher, Engineer, Entrepreneur, Environmentalist, Event planner, Explorer, Filmmaker, Finance professional, Foodie, Gay, Global soul, Hindu, Idea generator, Industrialist, Inventor, Investor, Jewish, Job-seeker, Journalist, Lawyer, Life mentor, Marketer, Musician, Muslim, Parent, Performer, Philanthropist, Photographer, Policy maker, Potential employer, Producer, Project manager, Promoter, Public servant, Real Estate professional, Sales specialist, Scientist, Single, Social entrepreneur, Startup, Student, Technologist, Web guru, World traveler, and Writer/Editor.

Share This

Next.

Previous.