Problems with Guest Accounts on Mac OS X

system, hacks, friends, education

Note: this applies to Leopard (10.5), not Snow Leopard (10.6); SL apparently has its own serious guest account problems. (Thanks, Harlan)

Today, a friend wanted to use my laptop at a meeting. I thought, cool, good thing Mac OS X has a "guest account" mechanism where a friend can log into a guest account and when they log out, it will be completely cleaned from my system.

However, when I clicked "Allow guests to log into this computer", something went wrong and the Mac "spinning beach ball" spun indefinitely. Damn.

It turns out that something in the backend expects a guest account to already exist in some form. Because it's not there, something critical crashes ("user account migration somehow confuses the 'guest user' machinery, which totally trashes securityd which dies of sudden death and from then on nothing works on the computer." via izidor).

Solving this problem is straight-forward but a bit of a pain in the ass.

  1. First, print this out or bookmark this page so you can come back to it.
  2. Force-quite system preferences and then you'll have to hold down the power key on your computer until it shuts down (feel free to try a restart, it won't work... it gets stuck in some sort of loop).
  3. Restart.
  4. Log in as an administrator.
  5. Your system guest account must be disabled (it already is if you have the described symptoms above).
  6. In the Accounts pane of System Preferences, Create new standard account with name guest and short name guest. Important: the short name must be guest---Mac OS will suggest the short name guest1, but you must edit that into guest.
  7. Enable the system guest account in System Preferences (check the "Allow guests to log into this computer" switch). It will work now that guest name is taken. This action will create user account with short name guest1 with all the properties of guest (clean-up after logout etc.).
  8. Completely delete standard user guest, which you created in step 6 (check "delete home folder" to get rid of it all).
  9. Disable the system guest account (uncheck the switch).
  10. Right-click on system guest account icon and choose "Advanced" or whatever (there is only one menu item anyway) and change short name from guest1 to guest.
  11. Enable system guest account.
  12. Log into the guest account.
  13. Log off as guest and log in with an admin account.
  14. Disable guest account in System Preferences.
  15. Go back to System Preferences, open the advanced settings of Guest Account and now you can safely rename the path of the home dir from /Users/Guest1 to /Users/Guest.
  16. Now re-enable guest account.
  17. The next time, you log in as guest, a new guest dir will be created with the correct name Guest.

ACCURATE comments on VVSG v1.1

elections, certification/testing, reform, standards, berkeley, friends, research, policy, usability

(Cross-posted on the ACCURATE blog: ACCURATE Comment on VVSG v1.1)

A Center for Correct, Usable, Reliable, Auditable and Transparent Elections (ACCURATE) submitted public comment today to the U.S. Election Assistance Commission on their draft Voluntary Voting System Guidelines, version 1.1 (VVSG v1.1). The VVSG provides national certification requirements and testing protocols for voting systems against which many states require their voting systems to be certified.

Full story »

Turn Off Dashes for Duplicate Authors in BiBTeX

hacks, open source

Occasionally, if you use LaTeX, you might find that a BiBTeX style file (a .bst file) replaces the name of duplicate authors with a dash. For example:

J. Doe. Anonymity. Anonymity Times 1(1) Nowhere, U.S.A., Jan. 2009.
?. Pseudonymity. Anonymity Times 4(8) Nowhere, U.S.A., Dec. 2009.

This might be a convention in some fields/disciplines/neuroses, but I think it's stupid and it's a pain in the ass when a journal or book tells you not to do it.

The solution? You have to replace the following line (or similar) from the relevant bibliographic style file (the appropriate .bst file):

FUNCTION {name.or.dash}
{ 's :=
   oldname empty$
     { s 'oldname := s }
     { s oldname =
         { "---" }   %% this is dumb
         { s 'oldname := s }
       if$
     }
   if$
}

and make it look like this (note only one line?the one with the comment?has changed):

FUNCTION {name.or.dash}
{ 's :=
   oldname empty$
     { s 'oldname := s }
     { s oldname =
         { oldname }   %% this is not dumb
         { s 'oldname := s }
       if$
     }
   if$
}

Viola!

We're married...

photos
It's official...

On the NYC Marriage Bureau waiting times...

system, wtf?, photos, family, friends, policy

I think I've told the world... but, if you don't know, here it is again: Chelle and I are getting married in a few weeks via a civil ceremony at the NYC Marriage Bureau. Michelle's parents, Pat and Dave, will be there and we're all pretty damn excited... yes, despite the fact that we've been together for 10.5 years.

Anyway, I wanted to comment a bit on the NYC Marriage Bureau's wait time estimates. They're not ideal. When we got there we were issued a sweet ass ticket:

Our number and timestamp

It has a timestamp (1:36pm) and our number, 143, is apparently the old pager code for "I love you" (thanks jo!).

Then the waiting began. When we first got there, the advertised wait time was 39 minutes. During that time, the wait time went down to as little as 15 minutes!

All in all, our number was called at 2:44pm, for a total wait time of 68 minutes. What the hell happened? I don't know. I think what happened is that the wait time is calculated as an instantaneous difference between the timestamps of the most recent two numbers to appear on the screen, and then the three values for the A, B, and C number pools are averaged. Why would I think that? Well, when started A113 was up on the screen and there were periods where the A numbers would pop up very quickly. During this time the wait time would go from, say, 53 minutes down to 15 minutes very quickly. Also, there were times where the B and C numbers didn't change at all and they stopped calling A numbers... and the aggregate wait time value would fall again.

Whatever they're doing, it would be more accurate to take the ticket from the customer, calculate the difference between the current time and the timestamp on their ticket, and use that quantity... rather than when the numbers show up on the screen.

We'll be waiting for probably 2 hours in our finest to get married here in a few weeks, so I'll just add 20% to the wait time and use that as a low bar!

UPDATE: BenAdida points to this great xkcd comic that is oh-so relevant to this post: http://xkcd.com/612/

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