On Tue, Apr 3, 2018 at 3:53 PM, Jeff Andich <jeff.and...@gmail.com> wrote: > Hi, > > When Linux and our application is running from eMMC, we wish to be able to > create log files on a uSD card plugged into the uSD slot on our board. > > I've ported some scripts which a former colleague wrote for the BeagleBone > Black that create a mount point on a factory default SD card if the SD card > exists, and re-formats the FAT to an ext4 partition. Basically they used a > udev script to trigger on the presence of /dev/mmcblk0p1 or /dev/mmcblk1p1 > and then call a shell script (from a systemd service launched by udev) for > formatting and mounting the SD card. > > One key thing that that shell script did was to detect where Linux was > running (e.g. /dev/mmcblk0p1 vs mmcblk1p1) based on examining the label of > the storage device, and then mounting the other device if it exists. This > capability to handle the '/' mount point "pingponging" between /dev/mmcblk0 > and mmcblk1 was needed due to the mount point changing for the eMMC > depending on whether an uSD card was plugged into the slot on the BeagleBone > Black with kernel 3.8.?. > > However, on the baseline images I've been using for the BB-X15, I haven't > yet observed any pingponging in that '/' always SEEMS to be mounted on > /dev/mmcblk1 when running from eMMC and /dev/mmcblk0p1 when running from uSD > card. I've been working with a BB-X15 console image consisting of (Debian > 8.10, kernel 4.4.110, and some variant of u-boot 2017.01), > > ?? Will this always be the case for the BB-X15 (and other devices) or at > least with the Debian version, kernel version, and u-boot version we're > using?? > > If so I'd like to take advantage of this fact in the shell script to only > create a mount point on the SD card when it doesn't contain a Linux image > and when '/' is mounted on /dev/mmcblk1p1. But I'm afraid that this > assumption may not hold and come back to bite us at some point.
According to my notes, this "randomness-race-label" condition was first "fixed" in the v4.5.x merge and "really" fixed in v4.5.3 We back-ported these two fixes to our v4.4.x-ti tree for the bbb and bbx15. https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?id=58821da858919f93f85c7e6823b49d439722a9e9 https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?id=520bd7a8b4152aacfbd34eb7f7a447354b631039 Regards, -- Robert Nelson https://rcn-ee.com/ -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/CAOCHtYiZCEhN%3D3vP6k8Tqkg-QE17pB53QDVVFUdbRvYHtwD%2BCg%40mail.gmail.com. For more options, visit https://groups.google.com/d/optout.
