Tag Archives: scale

Links: 4 Sep


  • grep tricks: grep files recursively, show only filenames where matching string was/wasn’t found.
  • Did you know that:
    • $ less <directory> — shows directory listing
    • $ less <archive.zip> — shows archive content
  • Teacher’s rumblings “Kids can’t use computers“. Agree to a T.
  • Going back to iPhone [from Android]. Again having pretty much the same thoughts.
  • Reddit: Lessons Learned From Mistakes Made Scaling To 1 Billion Pageviews A Month
  • Start a Web Search in a GUI Browser from the Command Line on Mac OS X
  • Screen recording to an animated GIF on Mac OS X
  • How to know from a child process that its parent exited:
    • a pipe between parent and a child, child gets SIGPIPE when parent exits
    • if a child has not detached, PPID becomes 1 when parent exits
    • Linux-specific: a child can ask kernel to deliver a signal when parent dies by specifying option PR_SET_PDEATHSIG in prctl() syscall
  • Two talks from YAC which I liked:

rpmdb locking issues, notorious on RHEL4/5, manifest as hanging rpm command. To see active locks:

# cd /var/lib/rpm; /usr/lib/rpm/rpmdb_stat -CA

Normally there should be no locks, given no rpm command is running. In case there are stale locks, just remove __db.00* files.


Sunlight in Europe and the USA in hours per year.

Links: 16 Aug


  • Cloud server showdown: Amazon AWS EC2 vs Linode vs DigitalOcean. AWS performance sucks, Linode winner.
  • Pull mode in orchestration’s rising star, Ansible. Check also out the web interface — AnsibleWorks AWX
  • Learning from other disciplines, nice quote:

    I’ve seen several college of engineering departments that have a sign that says the equivalent of, “If you cheat in engineering classes, you will kill people later”. We don’t have that mindset yet with IT, but I think we should because eventually, we’ll be responsible for infrastructure that will kill people if we get it wrong.

  • knockd — a port-knock server. It listens to all traffic on an ethernet (or PPP) interface, looking for special “knock” sequences of port-hits. A client makes these port-hits by sending a TCP (or UDP) packet to a port on the server. When the server detects a specific sequence of port-hits, it runs a command defined in its configuration file. This can be used to open up holes in a firewall for quick access.
  • Here’s the example of why LISA conferences rock: 2007 paper On Designing and Deploying Internet-Scale Services. Must read for sysadmins.
  • How to automatically setup and keep ssh tunnel up with autossh, available from macports


  • Steven Fry, one of my all-time favourite actors and activists, wrote an open letter petitioning for moving Winter Olimpics 2014 from Russia to elsewhere, because of wilful LGBT community oppressions. On a related note, sexual orientation forms during prenatal period, influenced by hormone levels, and is therefore inborn feature. Read about it in Russian.