On Wed, Nov 27, 2019 at 08:22:25AM -0500, Gene Heskett wrote: [...] > Doesn't look as if it will work with this preempt-rt kernel :( > > pi@rpi4:~/linuxcnc/configs/sheldon-lathe $ sudo /usr/sbin/tcpdump -i 7 > tcpdump: Can't open USB bus file /sys/kernel/debug/usbmon/1t: No such > file or directory Throwing the error message into a search engine yields some promising links: https://stackoverflow.com/questions/32740413/no-usb-bus-file-even-after-enabling-usbmon-in-android-kernel https://unix.stackexchange.com/questions/546719/no-such-file-or-directory-sys-kernel-debug-usb-usbmon So it seems you need the usbmon module loaded (is it?) and the debugfs pseudo file system mounted (again, is it?). HTH -- tomás
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