• 201409.18

    Sudoers syntax error for specific commands

    This will be short but sweet. When deploying some new servers today, I ran into a problem where no matter what, sudo bitched about syntax errors in my sudoers file. I tried a bunch of different options/whitespace tweaks/etc and nothing worked.

    deploy ALL= NOPASSWD: monit restart my-app

    Looks fine right? Nope.

    Use absolute paths

    This fixed it:

    deploy ALL= NOPASSWD: /usr/bin/monit restart my-app

    Everyone in the world's advice is to "just use visudo" but I couldn't find any info on what was actually causing the syntax error. Hopefully this helps a few lost souls.

  • 201006.07

    Strange problems with hosts resolving in PHP (and some other linux weirdness)

    This weekend I wen't on a frenzy. I turned beeets.com from a single VPS enterprise to 4 VPSs: 2 web (haproxy, nginx, php-fpm, sphinx, memcached, ndb_mgmd) and 2 database servers (ndmtd). There's still some work to do, but the entire setup seems to be functioning well.

    I had a few problems though. In PHP (just PHP, and nothing else) hosts were not resolving. The linux OS was resolving hosts just fine, but PHP couldn't. It was frustrating. Also, I was unable to sudo. I kept checking permissions on all my files in /etc, rebooting, checking again, etc.

    The fix

    Then I looked again. /etc itself was owned by andrew:users. Huh? I changed permissions back root:root, chmod 755. Everything works. Now some background.

    A while back, I wrote some software (bash + php) that makes it insanely easy to install software to several servers at once, and sync configurations for different sets of servers. It's called "ssync." It's not ready for release yet, but I can say without it, I'd have about 10% of the work done that I'd finished already. Ssync is a command-line utility that lets you set up servers (host, internal ip, external ip) and create groups. Each group has a set of install scripts and configuration files that can be synced to /etc. The configuration files are PHP scriptable, so instead of, say, adding all my hosts by hand to the /etc/hosts file, I can just loop over all servers in the group and add them automatically. Same with my www group, I can add a server to the "www" group in ssync, and all of a sudden the HAproxy config knows about the server.

    Here's the problem. When ssync was sending configuration files to /etc on remote servers, it was also setting permissions on those files (and folders) by default. This was because I was using -vaz, which attempts to preserve ownership, groupship, and permissions from the source (not good). I added some new params (so now it's "-vaz --no-p --no-g --no-o"). Completely fixed it.

  • 200910.15

    Really good article on OS scalability

    Compared are Linux 2.4, 2.6, FreeBSD, NetBSD, and OpenBSD. Really well-performed benchmarks, with graphs.


    Linux 2.6 was hands down the winner, which makes me feel good about Slackware (2.6 linux but actually stable) as a server. I'm sure Windows would have won if only it was benchmarked. One thing to keep in mind - from what I gathered, the machine tested was a single-processor, single-core machine...this means that SMP scalability was not tested, a HUGE consideration for more modern servers (what server now doesn't have multiple cores?) and may skew the modern-day results, especially between the two leads, FreeBSD and Linux 2.6.