Here's what I've found so far:
- There are two different messages I see when Pi-Star gets stuck in rw mode: mount: / is busy and mount: /: mount point is busy. I haven't yet identified the pattern for when each message gets displayed. It might be that mount: /: mount point is busy is the Buster message, but I'm not sure yet.
- If Pi-Star starts up in rw mode, I sometimes can use rpi-ro to kick it into ro mode, but other times not.
- If Pi-Star is in ro mode and I run sudo pistar-update, then it sometimes finishes in rw mode. Sometimes I can use rpi-ro to kick it into ro mode, but other times not.
- If I can't use rpi-ro to kick it into ro modes, then most of the time I can run sudo systemctl restart systemd-udevd.service followed by rpi-ro to kick it into ro mode. But sometimes that doesn't work, especially if Pi-Star starts up in rw mode.
If I can't use rpi-ro or sudo systemctl restart systemd-udevd.service followed by rpi-ro to kick it into ro mode, then the only thing I've found that works is rebooting.
- Just now, on RPi 4 hotspot running 4.1.0-RC6, Pi-Star started up in rw mode. It did not work to use rpi-ro to kick it into ro mode (message: mount: /: mount point is busy), but it did work to run sudo systemctl restart systemd-udevd.service followed by rpi-ro to kick it into ro mode.
Next, I ran sudo pistar-update. (Note: Most of the time, I run updates via SSH so I catch any OS updates, too, and today's update did include an OS update.) When the update was finished, it ended up in rw mode with the mount: /: mount point is busy message. Once again, running sudo systemctl restart systemd-udevd.service followed by rpi-ro did successfully kick it into ro mode.
- Earlier this morning, when I started up an RPi 3A+ hotspot running 4.1.0-RC6, Pi-Star started up in rw mode. It did not work to use rpi-ro to kick it into ro mode (unfortunately, I didn't pay to the exact mount is busy message that was displayed). Running sudo systemctl restart systemd-udevd.service followed by rpi-ro also didn't kick it into ro mode. In that case, I rebooted, and the second time it started up in ro mode.
P.S. Because I'm doing so many fresh image installs and configurations, I'm really falling in love with the RPi 4B. Even though it may be overkill for ordinary hotspot operations, it's so much faster whenever you need to install and do an initial configuration, when you run a pistar-update that includes an OS update, or simply when you Apply Changes on the Configuration page. Because of that, I I'm going to switch a couple more of my primary 3A+ hotspots to 4B. Yesterday, I noticed that Canakit has released a new fan case for the RPi 4B that looks pretty nice:
https://www.canakit.com/raspberry-pi-4-case-white.html (available in white, black, and clear).
So I ordered a couple, along with RPi 4B boards, fans, and their USB-C power switches, which I really like. They also have various all-included kits available, but I don't need any more microSD cards/readers or micro HDMI cables, so I put together my orders from their basic RPi 4B 1GB kit in order to save a few bucks (includes USB-C power supply and three heat sinks), and then added the other items from their other accessories list.
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