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July 2009 Archives

As a sysadmin at an international company I find myself doing more and more timezone conversions, and with a high frequency of errors. Thus, I rely on this site to make my life easier. Not only do they provide a great free service, but their web pages are bookmark-able in ways that let me use and re-use their stuff.

The site has many useful date and timezone calculations. If you want to know the time in New York City, Cambodia, or any other place you have (or haven't) hard of, they can do the calculation. You can even create URLs that display the current (or a particular) time for your favorite locations. They have calculators that do frequent but error-prone lookups that go beyond simple timezone calculations. How many days between today and Sunday, June 6, 2010? When is Easter Sunday in the US next year? When did I turn 1 million seconds old? Countdown clocks, eclipes, and so on are also available. It seems like they add new features every month.

Suppose you have offices in New York, London, and Shenzhen. You can create a URL that shows the current time at those offices. Bookmark it. Now if you need to make a phone call, check the bookmark before you dial. Simple.

Bookmarking these three URLs will save countless hours and prevent tons of embarrassing mistakes. (In these examples we'll pretend you have offices in San Francisco, New York, Dublin, Hyderabad, Beijing, Melbourne.)

  • Personal World Clock: This URL shows the current time at all six locations. Since it always shows the current time, this is useful for deciding whether or not it is apropriate to call someone in another office. I'm sure you can think of many other uses for this page. The URL encodes the list of locations. You can list dozens and dozens of locations so don't be afraid to list ever darn office in your company. Put the link on a highly visible place (like your internal intranet web site) so others can benefit. Here's a tip: Sort the countries west to east so the display is more logically ordered.
  • Meeting Planner: Suppose you need to set up a meeting. Click on this URL. The colors indicate when people might be sleeping or awake (Mnemonic: "red is bad") (again, the locations are sorted west to east). People in New York, Dublin and Hyderabad need a meeting? Move your mouse down to highly potential meeting times and look for where all the locations involved are "green." The optimal time for someone may be "tomorrow" for someone else, thus day of the week is included. Unsure when Daylight Saving Time kicks in for Dublin versus the US? Never fear. knows. Adjust the URL to the exact date and your timezone worries are over. This planner accepts only 6 locations therefore you might want to provide links on your internal web site that are appropriate for each division.
  • Friday, July 31, 2009 at 9:00:00 AM (NEW YORK TIME): Are your fingers getting tired listing the time and date for a meeting followed by conversions for all the timezones involved? Not only am I tired of this, but I tend to accidentally introduce typos or miscalculations when I try. Now I list only one time but create a link to a URL like this one that does the conversion for me. The link is easy to generate: it's taken from the meeting planner page. Some companies have a policy of only listing date/times in the timezone of their HQ. Linking to this URL makes it easier for everyone. (If a meeting has participants from 1 or 2 timezones I list both times right in the email. However, linking to a URL like this is even better).

For all of these I use the same list of locations consistently. It is the locations of the people I most frequently deal with. That way they get used to seeing the same set of countries. It encourages people to use the same list every time too.

Lastly, using a gobal calendaring system like Oracle Calendar, Microsoft Exchange, Google Apps and so on also reduces the need for people to manually convert timezones. However, even with these tools, we often want to list times and dates in emails or on web pages. is extremely useful in these cases. Using it makes us more efficient because it saves us time and prevent errors. When we place URLs like the ones above on our intranet homepage or use them in emails the use tends to spread virally (in the good sense of the word) and we create an multiplier effect improving efficiency throughout our organization.

Posted by Tom Limoncelli in Time Management

Friday, July 31 is Sysadmin Appreciation Day.  Sysadmins in NYC are gathering for dinner and beers at "The Gingerman", 11 E 36th St,New York, NY 10016.  More info on the Standalone Sysadmin blog: NYC Sysadmin Appreciation Day Gathering.

Update:  There will be a book give-away.  I'll be giving away an autographed copy of "Time Management for System Administrators".  Hope to see you there!

Posted by Tom Limoncelli in AppearancesArchive

(I'm setting up Debian PPC on an old PowerBook G4.)

The installation went really well.  I downloaded the stable 5.0.2 DVD image, burned it onto a DVD from my Mac (note: Safari warned that the file system might be corrupted, but I ran "md5" on the .iso and the output matched what the web site said it should be) and it booted without incident and I was able to go through the entire installation without fail.  I am cheating a little since I'm not doing a multi-boot.  I hear that is more difficult.

When the machine booted the first time I was able to log in!  Sadly, the touchpad wasn't working, and there was only so much I could do from the keyboard.

Using TAB and SPACEBAR I was able to navigate around a little.  Sometimes I would get into a corner where TAB nor SPACEBAR was really helpful.

Luckily you can always log out of an X11 session by pressing CTRL-OPTION-BACKSPACE. Warning: this zaps the entire X11 window session.  All your apps are instantly killed. You are logged out.  Don't press it unless you mean it.  (And, yes, the keyboard sequence is an homage to CTRL-ALT-DEL).  While this wasn't the best option, sometimes it was all I had.

To fix these problems I thought the best thing to do would be to SSH to it from another machine.  The default Debian configuration doesn't include openssh-server, just the -client.  This is wise from a security standpoint, but wasn't helping me fix the machine.

From the initial login screen I was able to set up a "Failsafe" xterm window.  From there I could become root.  "apt-get install ssh" tried to the right thing, but it couldn't get access the DVD drive.

"ls /dev" wasn't showing very much.  No /dev/sd* or hd* or sr0 (CD-ROM) at all.  This was distressing.  My touchpad wasn't working, my CD-ROM (well, DVD) wasn't showing up.

I couldn't load new packages if the DVD didn't work.  I couldn't fix the machine if I couldn't SSH in.  Ugh.

I searched a lot of web sites for information about how to fix this and nearly gave up.

Finally I remember that in the old days zapping the "PRAM" fixed a heck of a lot of problems.  The PRAM is a battery-backed bit of RAM (or NVRAM) that stores a few critical settings like boot parameters and such.  To zap the PRAM, you boot while holding these four keys: Command, Option, P and R.  It takes some practice.

After zapping the PRAM Debian booted and the mouse and touchpad magically worked.  When I logged in, I could see that the DVD was working.  "apt-get install ssh" worked without a hitch.  The DVD had automatically been detected and mounted.  I was impressed!

"ls /dev" now showed many, many more devices.

Later I installed SSH ("apt-get install ssh"), configure my SSH keys so I can log in easily from my primary computer, and even added the Ethernet MAC address to my DHCP server so that it always gets the same IP address.

To be honest, I don't know if zapping the PRAM fixed it or it was the reboot.  udevd may not have started (I forgot to check).  Either way, I was very happy that things worked.  I started up a web browser, went to and when it came up it felt like home.

Posted by Tom Limoncelli in Technical Tips

John Graham-Cumming wrote an excellent article about how Alan Turing, father of computer science, deserves an apology.  His explanation blew me away because of the beautiful symmetry (or maybe we should say "recursion") in the unfairness of how Turing was prosecuted when seen through the light of how Turing constructed his famous "Turing Test".

Posted by Tom Limoncelli in Community

Randy Bush makes an interesting financial point that might help you explain IPv6 to the finance people: Pay a little now or pay a lot in the future. Plus a very good point: Do a single service like making your DNS dual-stacked. You'll be more focused and you'll find where the problems are going to be.