How can I run continuous Logcat in the background?

You need root for this (where I was making mistakes).

So, in a terminal:

su

logcat V > /sdcard/logcat.txt

then, without killing the command, just press home to keep the terminal running in the background.

• V means verbose (the highest level of detail)


• D means debug

and there are other less detailed levels.

Exercise caution when sharing D and V level logs; they contain highly sensitive information.