Quick Quality-of-Life Improvements

[fiftyfourthparallel]

@fiftyfourthparallel

sys-usb: how to protect yourself against accidentally shutting it down

(I’ve suggested this in other places but can’t find them right now, so no link). If you’ve ever found yourself in the situation where you accidentally shut down sys-usb AND you happen to be using a USB keyboard or mouse, you’re basically hosed. Your machine will be a brick until you reboot it, because dom0 doesn’t take things like your keyboard and mouse back after they’ve been assigned to sys-usb. (This is not a bug, it’s a deliberate design decision taken for security reasons.)On the other hand, it’s safe to restart sys-usb from the qui-domains tool, and that fact is going to help us here.How to solve this? Create a cron job that starts sys-usb if it isn’t already running, and set that job to run every minute. (For those new to unix/linux, cron jobs are tasks that are prescheduled and run in the background. In the old days of stone knives-and-bearskins computing, these were often called “batch” jobs.) Here’s how to do that: Open a terminal in dom0 and type crontab -e. This opens the vi editor which will show you a file that contains existing user crontabs (as opposed to ones run by root). The file may well be empty. Insert a line that reads:

* * * * * qvm-start --skip-if-running sys-usb > /dev/null 2>&1

The five stars denote every minute of every hour of every day of every year. The middle part of the command should be self explanatory. The stuff after the > redirects the output of the command to /dev/null, which is basically “nowhere” rather than the screen or some log file.The result should be that if you shut sys-usb down for whatever reason, sometime within the next minute it should start back up again and you have your keyboard and mouse back.This edit only needs to be done once; it will still be there after restarting your system.The bad news is that in order to work with this, you have to know how to use vi…which is actually a tool adapted from those stone-knives-and-bearskin days. You can (if the file is empty) type i to get into “insert mode”, type the line above (including the return/enter at the end of the line), then press the escape key and type :wq to write and exit. @SteveC

Posting the original to serve as a thread-splitting header before I summarize it.