How do I fix this kernel panic on IMac El Capitan?

If your Mac spontaneously restarts or displays a message that it restarted or shut down because of a problem, click here --> https://support.apple.com/HT200553

errno 5 is an I/O error. launchd is a critical part of the operating system. It is the first process started after the kernel gets loaded.

It is possible you have a failing hard disk.

EtreCheck may detect if there have been disk errors.

https://etrecheck.com

You can use it in the Free Mode and post the output in an Additional Text box

Please post one or more panic reports

Finder -> Go (menu) -> Go to folder -> /Library/Logs/DiagnosticReports

Command-Shift-Period (may not work in El Capitan) will show invisible files. Look for files that end in the word .panic or .contents.panic and post them in an Additional Text box

Press Command-Shift-Period to hid the Finder invisible files again.