What is the "lsd" process on OS X, and why is it using so much CPU power?

lsd in OS X is indeed the LaunchServiceDaemon. launchd is a launch daemon manager! It provides probably the same function as in iOS. According to Apple it provides

support for launching apps and matching document types to apps. As a result, the keys recognized by Launch Services allow you to specify the desired execution environment for your bundled code.

lsd was apparently introduced in OS X 10.11 El Capitan because I can't find it in older systems. The latest version (included in 10.11.2) should have the mod date Dec 3, 2015.

To troubleshoot

• the "LaunchServices: Could not store lsd-identifiers file at /private/var/db/lsd/com.apple.lsdschemes.plist" problem check this post:

  Probably not the best way, but I seem to have fixed/suppressed that error message. This is what I did:

  cd /private/var/db

  lsd directory did not exist

  mkdir lsd

  Still no joy

  chmod -R 777 /private/var/db/lsd
  (i know, i just opened up my gibson to being hacked)
  touch /private/var/db/lsd/com.apple.lsdschemes.plist

  Seemed to go away after that. Willing to bet a disk repair/permissions check will break it again, but have not tried. If I cat that file the following is the content:

  bplist00?

• the 100 % CPU-usage: /usr/libexec/lsd using 100% of CPU

It seems that lsd gets stuck on _LSCreateRegistrationData for a certain app. If you're having the same issue, follow the guide below.

1. Open activity monitor and search for lsd
2. Get the PID of the lsd owned by the root user
3. Open the terminal
4. Enter sudo sample PID-HERE (Of course, replacing PID-HERE with the PID you got in step 2)
5. If you're having the same issue, there should be something about _LSCreateRegistrationData in the call graph (near the top of the whole output)
6. Enter sudo lsof -p PID-HERE

You should be able to recognise an app package within that output. Try deleting or updating it and see if it solves the issue