Unlockupd

Unlockupd is a software that tackles a system service bug called lookupd. It is a fundamental component of the Mac OS X without which the system becomes unusable. Unlockupd monitors the status of lookupd and forces it to restart if it fails. However, it is important to note that while Unlockupd has undergone significant testing, it should still be considered beta-quality. It was made available on the darwin-dev mailing list due to high demand.

Technical Details - Lookupd is responsible for handling NetInfo, DNS, and other requests related to lookup and caching. Applications do not interact directly with lookupd, but rather use standardized library functions that access lookupd on their behalf. Lookupd has a bug, which causes it to crash randomly, affecting its ability to clean up cache codes. The system crash log agent does not handle lookupd crashes effectively, leading to other applications hanging.

When lookupd stops responding, it becomes difficult to recover the system, although not impossible. One solution is to leave a root shell running and `killall -9 lookupd` when the issue is identified. However, this is not recommended as it requires lookupd services.

How Unlockupd Works - Unlockupd is a small daemon that monitors the status of lookupd. It periodically checks lookupd and takes note in the system log if it is not responding. To restore lookupd, Unlockupd terminates it.