FreeBSD on Samsung Chromebook "SNOW" model XE303C12
The Chromebook is an affordable computer powered by Samsung Exynos 5250 (ARMv7 Cortex A15) System-On-Chip
Supported Device Drivers
- Framebuffer
- Keyboard
- USB 2.0
- USB 3.0
Known Bugs/Limitations
WiFi is not supported
- Sound is not supported
- Power management is not supported, resulting in poor battery life
- Only Powered USB 2.0 hubs are supported
- Keyboard polling mode is not implemented and the keyboard will work unpredictably at the mountroot promt or in KDB
- Keyboard left arrow key does not work predictably at the command line
- Kernel will log "Spurious interrupt detected" (Switch to another console)
- SD Slot is not supported but can be used for kernel boot
- FreeBSD HEAD may constantly log "chrome_ec0: i2c transfer returned 4"
Synopsis
FreeBSD ARM can be booted on the Chromebook "SNOW" using a specially-configured USB boot device that contains a U-Boot boot loader partition, an msdos FreeBSD kernel partition and a UFS root partition
A true 4GB USB device will have room for the FreeBSD sources and an object directory and will build the default CHROMEBOOK-SNOW kernel in about 14 minutes, 30 seconds
An SD Card can be used for the U-Boot and kernel partitions but is not supported by FreeBSD for the FreeBSD root. SD Card boot has proved useful for USB debugging
Source Checkout
FreeBSD SVN tag 269385 is known to work
# svnlite co http://svn.freebsd.org/base/head@269385 /usr/src
Kernel Configuration
The default /usr/src/sys/arm/conf/CHROMEBOOK-SNOW kernel configuration file requires the following additional options to support USB root boot:
nooptions ROOTDEVNAME options ROOTDEVNAME=\"ufs:/dev/da0p3\"
Kernel and World Build
# make TARGET_ARCH=armv6 KERNCONF=CHROMEBOOK-SNOW buildworld buildkernel
Use a -j jobs that is appropriate for your hardware
USB Device Partitioning
Change "da0" to match your attached USB device
Warning: This will delete all data on the USB device
# gpart delete -i 1 da0 # gpart delete -i 2 da0 # gpart delete -i 3 da0 # gpart destroy da0 # dd if=/dev/zero of=/dev/da0 bs=1m count=32 # gpart create -s GPT da0 # gpart add -b 1m -s 15m -t \!fe3a2a5d-4f32-41a7-b725-accc3285a309 da0 # gpart add -b 17m -s 15m -t \!fe3a2a5d-4f32-41a7-b725-accc3285a309 da0 # gpart add -t freebsd-ufs da0
You can optionally create a swap partition after the freebsd-ufs partition
Sample output from a 3.7GB "4GB" device is:
# gpart show da0
=> 34 7821245 da0 GPT (3.7G)
34 2014 - free - (1.0M)
2048 30720 1 !fe3a2a5d-4f32-41a7-b725-accc3285a309 (15M)
32768 2048 - free - (1.0M)
34816 30720 2 !fe3a2a5d-4f32-41a7-b725-accc3285a309 (15M)
65536 7755743 3 freebsd-ufs (3.7G)
Populating the U-Boot Partition
# fetch http://commondatastorage.googleapis.com/chromeos-localmirror/distfiles/nv_uboot-snow-simplefb.kpart.bz2 # bunzip2 nv_uboot-snow-simplefb.kpart.bz2 # dd if=nv_uboot-snow-simplefb.kpart of=/dev/da0p1 bs=1m
Also note: http://linux-exynos.org/dist/chromebook/nv_uboot/
Populating the Kernel Partition
# newfs_msdos /dev/da0p2 # mount_msdosfs /dev/da0p2 /mnt # cp /usr/obj/arm.armv6/usr/src/sys/CHROMEBOOK-SNOW/kernel.bin /mnt/ # umount /mnt
Populating the Root Partition
# newfs -U /dev/da0p3 # mount /dev/da0p3 /mnt # cd /usr/src/ # make TARGET_ARCH=armv6 DESTDIR=/mnt installworld distribution # echo "/dev/da0p3 / ufs rw,noatime 1 1" > /mnt/etc/fstab # vi /mnt/etc/ttys < Change ttyv0 thorough ttyv4 from "off" to "on" > # umount /mnt
You can optionally copy in your /usr/src and /usr/obj/ to the USB image prior to unmounting
You may now remove the USB device and insert it into the USB 2.0 port (between the HDMI connector and USB 3.0 port on the Chromebook
Chromebook Commands
Enable Developer Mode
The Chromebook must be placed in "Developer Mode" to enable USB/SD Card boot. This step only needs to be performed once
WARNING: This will delete all personal data and settings on your Chromebook
- Power the machine off using the Linux GUI or by holding down the Power button
- Hold down ESC and Refresh (above the "4" key) keys, and press the Power button
- This will enter Recovery mode. Press CTRL+D to enter Developer mode
- Press Enter to confirm
- You now see the "OS verification is OFF" screen. Press CTRL+D to continue
- Wait approximately 5 minutes for the procedure to complete
Access the GNU/Linux Command Line
You will need the Chromebook's GNU/Linux command line for some steps
- Power the machine on and either press CTRL+D at the "OS verification is OFF" screen or wait for the two tones
Change to the second virtual console by pressing CTRL+ALT and the "=>" button (above the "3" key)
Enable USB/SD Card Boot
This step only needs to be performed once from the GNU/Linux command line:
localhost login: root localhost ~ # crossystem dev_boot_usb=1 localhost ~ # reboot
To verify this setting:
localhost ~ # crossystem --all | grep dev_boot_usb localhost ~ # dev_boot_usb = 1 # Enable developer mode boot from USB/SD (writable)
Restart
- Type 'reboot' at the GNU/Linux command line if available
- Press the Refresh (above the "4" key) and Power keys
Power Off
- Click "Shut down" on the bottom left of the GNU/Linux GUI
- Issue the GNU/Linux or FreeBSD shutdown command
- Hold down the Power button
Mark the FreeBSD USB Device Bootable
This step must be performed on the GNU/Linux command line for every newly created USB or SD Card device
For a USB device:
# cgpt add -P 12 -T 5 -S 1 -i 1 /dev/sda # reboot
To review the partition table:
cgpt show /dev/sda ... Attr: priority=12 tries=5 successful=1 ...
For an SD Card device:
# cgpt add -P 12 -T 5 -S 1 -i 1 /dev/mmcblk1 # reboot
To review the partition table:
cgpt show /dev/mmcbkl1 ... Attr: priority=12 tries=5 successful=1 ...
Booting with U-Boot
- Insert your USB device if not inserted already
- Power the machine on and press CTRL+U on the
- Insert USB flash device to USB 2.0 port and insert SD card
- Power on laptop and press CTRL+U at the "OS verification is OFF" screen. If it beeps at you, your USB/SD Card is not properly configured
- In U-boot type:
For a USB device:
SMDK5250 # usb start SMDK5250 # usb dev 0 SMDK5250 # fatload usb 0:2 0x40f00000 kernel.bin SMDK5250 # go 0x40f00000
This can be saved with:
SMDK5250 # setenv bootcmd "usb start; usb dev 0; fatload usb 0:2 0x40f00000 kernel.bin; go 0x40f00000" SMDK5250 # saveenv SMDK5250 # boot
For an SD Card device:
SMDK5250 # mmc dev 1 SMDK5250 # mmc rescan 1 SMDK5250 # fatload mmc 1:2 0x40f00000 kernel.bin SMDK5250 # go 0x40f00000
This can be saved with:
SMDK5250 # setenv bootcmd "mmc dev 1; mmc rescan 1; fatload mmc 1:2 0x40f00000 kernel.bin; go 0x40f00000" SMDK5250 # saveenv SMDK5250 # boot
If you have saved your U-Boot command, you can interrupt the autoboot by pressing any key
Useful information
Change GNU/Linux and FreeBSD Consoles: Hold down CTRL+ALT and press "=>" button (located above the "3" key). This is very useful when the console is flooded with "Spurious interrupt detected" messages
Remember that the FreeBSD kernel is on /dev/da0p2 should you build a new kernel
# mount_msdosfs /dev/da0p2 /mnt # ls /mnt kernel.bin # cp /usr/obj/arm.armv6/usr/src/sys/CHROMEBOOK-SNOW/kernel.bin /mnt/ # umount /mnt
Chromebook information: http://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices/samsung-arm-chromebook
Chromebook partitioning information: http://www.chromium.org/chromium-os/chromiumos-design-docs/disk-format#TOC-Partition-types
Chromebook "snow", "peach pit" and "spring" models explained: http://www.chromium.org/chromium-os/developer-information-for-chrome-os-devices
Samsung Chromebook2 "PEACH PIT" model XE503C12
This model has a Samsung Exynos 5420 (effectively quad-core) CPU with 3.5GB of usable RAM and a supported SDHC port
The only changes to the above instructions are:
- The kernel config to use is CHROMEBOOK-PEACH-PIT
The U-Boot firmware is available at http://linux-exynos.org/dist/chromebook/nv_uboot/nv_uboot-peach-pit.kpart
HP Chromebook 11 "SPRING" model 11-1101
This model has a Samsung Exynos 5250 Dual 1.7 GHz CPU and 2GB RAM
- The kernel config to use is CHROMEBOOK-SPRING
The U-Boot firmware is available at http://linux-exynos.org/dist/chromebook/nv_uboot/nv_uboot-spring.kpart