Very interesting concept. Thanks for sharing your proof of concept.
Tell everyone at sketching hello! Drew On Sat, Sep 28, 2019, 20:13 Jason Kridner <[email protected]> wrote: > I’m attending Sketching in Hardware <http://sketching-in-hardware.com/> this > weekend and there was a fair bit of discussion regarding how long it takes > to boot Linux and barriers it makes to understanding a system. My assertion > was that booting Linux on a computer, like PocketBeagle, doesn’t take very > long at all and that it generally only gets in the way when you want it. > > Here’s what I hacked up in about 10 minutes to show off how we can get a > whole lot of distribution code out-of-the-way. > > In /boot/uEnv.txt, I edited the cmdline: > > cmdline=coherent_pool=1M net.ifnames=0 rng_core.default_quality=100 quiet > *modules-load=g_serial* > > The point of this is that our boot script that configures the USB gadget > won’t be loaded anymore. This causes the Linux kernel to emulate a serial > port, providing a way to get to the Python REPL. > > In /etc/passwd, I edited the shell for the ‘debian’ user: > > debian:x:1000:1000:Demo User:/home/debian:*/usr/bin/python3* > > This makes python3 the default shell for the ‘debian’ user, so whenever a > user logs in as ‘debian’, they get a python3 REPL. > > In /lib/systemd/system/[email protected], I enabled a bypass for the > user login password request: > > ExecStart=-/sbin/agetty --keep-baud 115200,38400,9600 %I $TERM* -a debian* > > This totally insecure, but on PocketBeagle without any augmentation, this > just gives access over the USB port. Seems pretty reasonable to me. > > I executed the following commands to reduce the applications running at > startup and enable the terminal on the virtual serial port: > > sudo systemctl set-default rescue.target > sudo ln -s /lib/systemd/system/[email protected] > /etc/systemd/system/default.target.wants/[email protected] > > When you do the above, a reboot will no longer bring up things like the > Cloud9 IDE, so be sure to run both commands before rebooting. Use ‘sudo > shutdown -r now’ to reboot. > > Seems like there’s still a fair amount of optimization that can be done, > but here’s the behavior I saw when pulling and re-inserting the USB cable > after making these changes: > > jkridner@tupper:~$ *journalctl -f* > Sep 28 13:55:52 tupper kernel: usb 1-4: USB disconnect, device number 26 > Sep 28 13:55:52 tupper upowerd[2124]: unhandled action 'unbind' on > /sys/devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4:2.1 > Sep 28 13:55:52 tupper upowerd[2124]: unhandled action 'unbind' on > /sys/devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4:2.0 > Sep 28 13:55:52 tupper upowerd[2124]: unhandled action 'unbind' on > /sys/devices/pci0000:00/0000:00:14.0/usb1/1-4 > Sep 28 13:56:08 tupper kernel: usb 1-4: new high-speed USB device number 27 > using xhci_hcd > Sep 28 13:56:08 tupper kernel: usb 1-4: New USB device found, idVendor=0525, > idProduct=a4a7 > Sep 28 13:56:08 tupper kernel: usb 1-4: New USB device strings: Mfr=1, > Product=2, SerialNumber=0 > Sep 28 13:56:08 tupper kernel: usb 1-4: Product: Gadget Serial v2.4 > Sep 28 13:56:08 tupper kernel: usb 1-4: Manufacturer: Linux 4.14.108-ti-r113 > with musb-hdrc > Sep 28 13:56:08 tupper kernel: cdc_acm 1-4:2.0: ttyACM0: USB ACM device > > So, without any other tweaking, it seems to still be taking about 16 > seconds. I’m not very happy with this, so I’ll be hooking up a serial cable > and figuring out where the time goes soon. > > jkridner@tupper:~$ *tio /dev/ttyACM0* > [tio 14:02:10] tio v1.29 > [tio 14:02:10] Press ctrl-t q to quit > [tio 14:02:10] Connected > > File "", line 0 > > ^ > SyntaxError: 'utf-8' codec can't decode byte 0xf0 in position 2: invalid > continuation byte > >>> quit() > > Debian GNU/Linux 9 beaglebone ttyGS0 > > BeagleBoard.org Debian Image 2019-08-03 > > Support/FAQ: http://elinux.org/Beagleboard:BeagleBoneBlack_Debian > > default username:password is [debian:temppwd] > > beaglebone login: debian (automatic login) > > Last login: Sun Aug 4 02:10:35 UTC 2019 on ttyGS0 > > The programs included with the Debian GNU/Linux system are free software; > the exact distribution terms for each program are described in the > individual files in /usr/share/doc/*/copyright. > > Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent > permitted by applicable law. > Python 3.5.3 (default, Sep 27 2018, 17:25:39) > [GCC 6.3.0 20170516] on linux > Type "help", "copyright", "credits" or "license" for more information. > >>> *import os* > >>> *os.system("bash")* > debian@beaglebone:~$ > > I chose to use ‘tio’, but ‘screen’ and other serial utilities would work > fine. > > I don’t actually know that the cause of the stray characters is. Someone > can probably enlighten me. > > I’ll release this as a blog post once I figure out why the boot time is > this slow, but I thought this was interesting enough to post here. Enjoy. > > -- > https://beagleboard.org/about > > -- > You received this message because you are subscribed to the Google Groups > "Beagle Alpha" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagle-alpha/CA%2BT6QP%3DK6UNOHjzrBV1%3DMDfSiBQb6R3_HMBg76Q_vkA1Z6uxXg%40mail.gmail.com > <https://groups.google.com/d/msgid/beagle-alpha/CA%2BT6QP%3DK6UNOHjzrBV1%3DMDfSiBQb6R3_HMBg76Q_vkA1Z6uxXg%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. 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