This is how to create a OS X El Capitan installer on a flash disk or external disk.
Download OS X El Capitan from the App Store. When it finishes downloading, quit the installer. The “Install OS X El Capitan” application should be in your /Applications folder. On a side note even if you do not create a bootable installer, it’s a good idea to get a backup of this installer before running it. After upgrading your system, the installer will remove itself.
Format a flash stick Mac OS Extended (Journaled) with GUID Partition Table
Name the disk “Untitled”. Simply because the command below references the disk by the “Untitled” name.
When you touch the Messages title bar, then click somewhere else on your screen, the messages app will move as if you dragged it. Such a strange bug and it was not sadly addressed in 10.10.1. Reproducible on any Mac, every time. How this could slip past QA is beyond me.
Came across this technique to get a screen session started as another non-root user on system startup. You could have this command in /etc/rc.local or any other location that runs on system startup as root.
Also, it doesn’t have to just be at system startup. These commands could be used at any time by the root user to start a screen session for another user.
This command must run as root. I had best luck when providing full paths to the executable and optional file arguments (like if you are passing a conf file)
su - username -c "/usr/bin/screen -dmS screenname ./executable"
So, for example, to get irssi started as chris in a screen session named irc, You could:
su - chris -c "/usr/bin/screen -dmS irc /usr/bin/irssi"
You can then log in to the box as chris and resume the screen session that root started.