Difference between revisions of "EBC Exercise 08 Installing Development Tools 4.4"

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m (Updating scripts before updating the Kernel: Removed)
(updated to working github link for the RobertCNelson ti-linux-kernel-dev)
 
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These notes taken from [http://www.youtube.com/watch?v=HJ9nUqYMjqs&t=4m10s Beaglebone: Adding USB Wi-Fi & Building a Linux Kernel] starting around 4 minutes and ending around 21 minutes.  Uses kernel from [http://eewiki.net/display/linuxonarm/BeagleBone+Black Robert C. Nelson's BeagleBone Black] page.
 
These notes taken from [http://www.youtube.com/watch?v=HJ9nUqYMjqs&t=4m10s Beaglebone: Adding USB Wi-Fi & Building a Linux Kernel] starting around 4 minutes and ending around 21 minutes.  Uses kernel from [http://eewiki.net/display/linuxonarm/BeagleBone+Black Robert C. Nelson's BeagleBone Black] page.
  
  host$ '''git clone git@github.com:RobertCNelson/ti-linux-kernel-dev.git'''  (42M)
+
  host$ '''git clone https://github.com/RobertCNelson/ti-linux-kernel-dev.git'''  (65M)
 
  host$ '''cd ti-linux-kernel-dev'''
 
  host$ '''cd ti-linux-kernel-dev'''
  host$ '''git tag'''
+
 
The last command lists all the versions of the kernel that are available.  Pick one and check it out. I usually pick the one with the highest
+
  host$ '''git tag | wc'''
version number.
+
    1857    1857  32406
  host$ '''git checkout 5.10.120-ti-r48 -b 5.10.120-ti-r4'''
+
The last command lists all the versions of the kernel that are available and counts them. There are over 1700 versions!
  Switched to a new branch 'git checkout 5.10.120-ti-r48 -b 5.10.120-ti-r48'
+
Let's narrow it a bit.
 +
host$ '''git tag | grep 5.10.168'''
 +
  5.10.168-ti-arm64-r100
 +
5.10.168-ti-arm64-r101
 +
...
 +
5.10.168-ti-arm64-r112
 +
5.10.168-ti-arm64-r113
 +
5.10.168-ti-r60
 +
5.10.168-ti-r61
 +
...
 +
5.10.168-ti-r69
 +
5.10.168-ti-r70
 +
5.10.168-ti-r71
 +
5.10.168-ti-r72
 +
5.10.168-ti-r73
 +
5.10.168-ti-r74
 +
5.10.168-ti-rt-r60
 +
5.10.168-ti-rt-r61
 +
...
 +
5.10.168-ti-rt-r69
 +
5.10.168-ti-rt-r70
 +
5.10.168-ti-rt-r71
 +
5.10.168-ti-rt-r72
 +
5.10.168-ti-rt-r73
 +
5.10.168-ti-rt-r74
 +
Pick one and check it out. I usually pick the one with the highest
 +
version number not equal to the version I'm running.
 +
  host$ '''git checkout 5.10.168-ti-r74 -b 5.10.168-ti-r74'''
 +
  Switched to a new branch '5.10.168-ti-r74'
  
 
Now at this point you have a choice, you can run '''./build_kernel.sh'''
 
Now at this point you have a choice, you can run '''./build_kernel.sh'''
Line 27: Line 55:
 
one '''.deb''' install file.  I suggest running '''./build_deb.sh''',
 
one '''.deb''' install file.  I suggest running '''./build_deb.sh''',
  
  host$ '''./build_kernel.sh''' or '''./build_deb.sh'''
+
  host$ '''./build_deb.sh'''
  + Detected build host [Ubuntu 20.04.1 LTS]
+
  + Detected build host [Ubuntu 22.04.3 LTS]
 
  + host: [x86_64]
 
  + host: [x86_64]
  + git HEAD commit: [a7ff6610037f33b2a8c19d7f111cf9e43aa3c4ef]
+
  + git HEAD commit: [1f23d7ca554505f54938ba393020c50b2ed9ced2]
 
  -----------------------------
 
  -----------------------------
 
  cpio: cpio (GNU cpio) 2.13
 
  cpio: cpio (GNU cpio) 2.13
  You're missing command lzop
+
  You're missing command lz4
 
  Please install missing commands
 
  Please install missing commands
 
  -----------------------------
 
  -----------------------------
Line 39: Line 67:
 
You ''may'' need to install some additional files.  Run the suggested commands.
 
You ''may'' need to install some additional files.  Run the suggested commands.
  
  host$ '''sudo apt-get update'''
+
  host$ '''sudo apt update'''
 
  host$ '''sudo apt install lzop'''
 
  host$ '''sudo apt install lzop'''
 
  host$ '''./build_deb.sh'''
 
  host$ '''./build_deb.sh'''
Line 60: Line 88:
 
Then run again.
 
Then run again.
 
  host$ '''./build_deb.sh'''
 
  host$ '''./build_deb.sh'''
  + Detected build host [Ubuntu 20.04.1 LTS]
+
  + Detected build host [Ubuntu 22.04.3 LTS]
 
  + host: [x86_64]
 
  + host: [x86_64]
  + git HEAD commit: [a7ff6610037f33b2a8c19d7f111cf9e43aa3c4ef]
+
  + git HEAD commit: [1f23d7ca554505f54938ba393020c50b2ed9ced2]
 
  -----------------------------
 
  -----------------------------
 
  cpio: cpio (GNU cpio) 2.13
 
  cpio: cpio (GNU cpio) 2.13
  lzop: lzop 1.04
+
  lz4: *** LZ4 command line interface 64-bits v1.9.3, by Yann Collet ***
  '/home/mark_a_yoder/BeagleBoard/bb-kernel/system.sh.sample' -> '/home/mark_a_yoder/BeagleBoard/bb-kernel/system.sh'
+
  '/home/yoder/ti-linux-kernel-dev/system.sh.sample' -> '/home/yoder/ti-linux-kernel-dev/system.sh'
  Installing Toolchain: gcc_arm_gnueabihf_9
+
glibc: 2.35
-----------------------------
+
  Installing Toolchain: gcc_10_arm
  
 
At this point the scripts are downloading the cross compiler, the kernel sources and anything else you need to compile the kernel for the bone.
 
At this point the scripts are downloading the cross compiler, the kernel sources and anything else you need to compile the kernel for the bone.
Line 77: Line 105:
 
[[File:KernelConfig2.png]]
 
[[File:KernelConfig2.png]]
  
Hit the right arrow to select '''Exit''' and then hit ENTER.  The compilation will continue.
+
Hit the right arrow to select '''Exit''' and then hit ENTER.   
 +
 
 +
The compilation will continue.  It took some 23 minutes on my laptop.
  
 
=== Installing the Kernel on Your Bone ===
 
=== Installing the Kernel on Your Bone ===
Line 98: Line 128:
 
  1.1M linux-libc-dev_1xross_armhf.deb
 
  1.1M linux-libc-dev_1xross_armhf.deb
  
The '''linux-image-''' file is the one we want. It contains nearly 3000 files.
+
The '''linux-image-''' file is the one we want. It contains over 3000 files.
 
  host$ '''dpkg -c linux-image-5.8.11-bone17_1xross_armhf.deb  | wc
 
  host$ '''dpkg -c linux-image-5.8.11-bone17_1xross_armhf.deb  | wc
     2981   17886 342664
+
     3252   19512 379622
 
The dpkg command lists all the files in the .deb file and the '''wc''' counts
 
The dpkg command lists all the files in the .deb file and the '''wc''' counts
 
all the lines in the output.  You can see those files with:
 
all the lines in the output.  You can see those files with:
  bone$ '''dpkg -c linux-image-5.8.11-bone17_1xross_armhf.deb  | less'''
+
  host$ '''dpkg -c linux-image-5.8.11-bone17_1xross_armhf.deb  | less'''
 
  drwxr-xr-x root/root        0 2020-09-29 14:16 ./
 
  drwxr-xr-x root/root        0 2020-09-29 14:16 ./
 
  drwxr-xr-x root/root        0 2020-09-29 14:16 ./boot/
 
  drwxr-xr-x root/root        0 2020-09-29 14:16 ./boot/
Line 118: Line 148:
  
 
Move the '''linux-image-''' file to your Bone.
 
Move the '''linux-image-''' file to your Bone.
  host$ '''scp linux-image-5.8.11-bone17_1xross_armhf.deb bone:.'''
+
  host$ '''scp linux-image-5.10.168-ti-r74_1xross_armhf.deb bone:.'''
  
 
Hint: You might have to add '''-P<port>''' if you changed your port number.
 
Hint: You might have to add '''-P<port>''' if you changed your port number.
Line 125: Line 155:
 
Now ssh to the bone.
 
Now ssh to the bone.
 
  host$ '''ssh bone'''
 
  host$ '''ssh bone'''
  bone$ '''ls -sh'''
+
  bone$ '''ls'''
  bin  exercises linux-image-5.8.11-bone17_1xross_armhf.deb
+
  bin  exercises linux-image-5.10.168-ti-r74_1xross_armhf.deb
 
Now install it.
 
Now install it.
 
  bone$ '''sudo dpkg --install linux-image-5.8.11-bone17_1xross_armhf.deb'''
 
  bone$ '''sudo dpkg --install linux-image-5.8.11-bone17_1xross_armhf.deb'''
 
Wait a while. Once done check /boot.
 
Wait a while. Once done check /boot.
 
  bone$ '''ls -sh /boot'''
 
  bone$ '''ls -sh /boot'''
  total 40M
+
  total 70M
  160K config-4.19.94-ti-r50     4.0K SOC.sh                    4.0K uEnv.txt.orig
+
  4.0K SOC.sh                      188K config-5.10.168-ti-r74     4.0K uboot
  180K config-5.8.11-bone17      3.5M System.map-4.19.94-ti-r50  9.7M vmlinuz-4.19.94-ti-r50
+
4.6M System.map-5.10.168-ti-r72  4.0K dtbs                        11M vmlinuz-5.10.168-ti-r72
  4.0K dtbs                      4.1M System.map-5.8.11-bone17   8.6M vmlinuz-5.8.11-bone17
+
  4.6M System.map-5.10.168-ti-r73  7.5M initrd.img-5.10.168-ti-r72  11M vmlinuz-5.10.168-ti-r73
  6.4M initrd.img-4.19.94-ti-r50  4.0K uboot
+
  4.6M System.map-5.10.168-ti-r74  7.8M initrd.img-5.10.168-ti-r73   11M vmlinuz-5.10.168-ti-r74
  6.8M initrd.img-5.8.11-bone17  4.0K uEnv.txt
+
  188K config-5.10.168-ti-r72      7.8M initrd.img-5.10.168-ti-r74
 +
  188K config-5.10.168-ti-r73      4.0K uEnv.txt
 
You see the new kernel files.  Check uEnv.txt.
 
You see the new kernel files.  Check uEnv.txt.
 
  bone$ '''head /boot/uEnv.txt'''
 
  bone$ '''head /boot/uEnv.txt'''
 
  #Docs: http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0
 
  #Docs: http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0
  # uname_r=4.19.94-ti-r50
+
  uname_r=5.10.168-ti-r73
  uname_r=5.8.11-bone17
+
  # uname_r=5.10.168-ti-r74
 
I added the commented out '''uname_r''' line to make it easy to switch between
 
I added the commented out '''uname_r''' line to make it easy to switch between
 
versions of the kernel.
 
versions of the kernel.

Latest revision as of 12:58, 11 January 2024

thumb‎ Embedded Linux Class by Mark A. Yoder


Early in the class most of the exercises we will do will all run on the BeagleBoard. You'll be able to edit (cloud9), compile (gcc) and run all on the Beagle. Later, when we start compiling the kernel or the boot loader, (U-boot) you will need to cross compile on a Linux machine and copy the results to the Beagle.

The purpose of this exercise is to install all the tools needed for compiling on your host so they will be ready when you need them.

Tip: Run this exercise using a wired connection if you can. The Ubuntu wireless driver can be finicky, and if it stops working you'll have to restart some of this.

The 5.x Kernel

Getting the 5.x Kernel

These notes taken from Beaglebone: Adding USB Wi-Fi & Building a Linux Kernel starting around 4 minutes and ending around 21 minutes. Uses kernel from Robert C. Nelson's BeagleBone Black page.

host$ git clone https://github.com/RobertCNelson/ti-linux-kernel-dev.git  (65M)
host$ cd ti-linux-kernel-dev
host$ git tag | wc
   1857    1857   32406

The last command lists all the versions of the kernel that are available and counts them. There are over 1700 versions! Let's narrow it a bit.

host$ git tag | grep 5.10.168
5.10.168-ti-arm64-r100
5.10.168-ti-arm64-r101
...
5.10.168-ti-arm64-r112
5.10.168-ti-arm64-r113
5.10.168-ti-r60
5.10.168-ti-r61
...
5.10.168-ti-r69
5.10.168-ti-r70
5.10.168-ti-r71
5.10.168-ti-r72
5.10.168-ti-r73
5.10.168-ti-r74
5.10.168-ti-rt-r60
5.10.168-ti-rt-r61
...
5.10.168-ti-rt-r69
5.10.168-ti-rt-r70
5.10.168-ti-rt-r71
5.10.168-ti-rt-r72
5.10.168-ti-rt-r73
5.10.168-ti-rt-r74 

Pick one and check it out. I usually pick the one with the highest version number not equal to the version I'm running.

host$ git checkout 5.10.168-ti-r74 -b 5.10.168-ti-r74
Switched to a new branch '5.10.168-ti-r74'

Now at this point you have a choice, you can run ./build_kernel.sh and build the kernel, or run ./build_deb.sh which will also build the kernel, but it will combine all the output files in one .deb install file. I suggest running ./build_deb.sh,

host$ ./build_deb.sh
+ Detected build host [Ubuntu 22.04.3 LTS]
+ host: [x86_64]
+ git HEAD commit: [1f23d7ca554505f54938ba393020c50b2ed9ced2]
-----------------------------
cpio: cpio (GNU cpio) 2.13
You're missing command lz4
Please install missing commands
-----------------------------

You may need to install some additional files. Run the suggested commands.

host$ sudo apt update
host$ sudo apt install lzop
host$ ./build_deb.sh
+ Detected build host [Ubuntu 20.04.1 LTS]
+ host: [x86_64]
+ git HEAD commit: [a7ff6610037f33b2a8c19d7f111cf9e43aa3c4ef]
-----------------------------
cpio: cpio (GNU cpio) 2.13
lzop: lzop 1.04
Debian/Ubuntu/Mint: missing dependencies, please install:
-----------------------------
sudo apt-get update
sudo apt-get install build-essential fakeroot lzma gettext bison flex pkg-config libmpc-dev u-boot-tools libncurses5-dev:amd64
 libssl-dev:amd64 
-----------------------------
* Failed dependency check

host$ sudo apt-get install build-essential fakeroot lzma gettext bison flex pkg-config libmpc-dev u-boot-tools libncurses5-dev:amd64 libssl-dev:amd64 libssl-dev:amd64

Then run again.

host$ ./build_deb.sh
+ Detected build host [Ubuntu 22.04.3 LTS]
+ host: [x86_64]
+ git HEAD commit: [1f23d7ca554505f54938ba393020c50b2ed9ced2]
-----------------------------
cpio: cpio (GNU cpio) 2.13
lz4: *** LZ4 command line interface 64-bits v1.9.3, by Yann Collet ***
'/home/yoder/ti-linux-kernel-dev/system.sh.sample' -> '/home/yoder/ti-linux-kernel-dev/system.sh'
glibc: 2.35
Installing Toolchain: gcc_10_arm

At this point the scripts are downloading the cross compiler, the kernel sources and anything else you need to compile the kernel for the bone.

Building the 5.x Kernel

At some point you will see

KernelConfig2.png

Hit the right arrow to select Exit and then hit ENTER.

The compilation will continue. It took some 23 minutes on my laptop.

Installing the Kernel on Your Bone

The following are three ways you can use to install a new kernel on your Bone. The first method works if you ran build_deb.sh.

The other two methods are used if you ran build_kernel.sh

You only need to use one method. If you ran build_kernel.sh I suggest you use the second one since you don't have to remove the SD card from the bone.

Installing the kernel package - build_deb.sh

The ./build_deb.sh script creates a single .deb file that contains all the files needed for the new kernel. You find it here:

host$ cd ti-linux-kernel-dev/deploy
host$ ls -sh
total 40M
7.3M linux-headers-5.8.11-bone17_1xross_armhf.deb  8.0K linux-upstream_1xross_armhf.buildinfo
 31M linux-image-5.8.11-bone17_1xross_armhf.deb    4.0K linux-upstream_1xross_armhf.changes
1.1M linux-libc-dev_1xross_armhf.deb

The linux-image- file is the one we want. It contains over 3000 files.

host$ dpkg -c linux-image-5.8.11-bone17_1xross_armhf.deb  | wc
   3252   19512  379622

The dpkg command lists all the files in the .deb file and the wc counts all the lines in the output. You can see those files with:

host$ dpkg -c linux-image-5.8.11-bone17_1xross_armhf.deb  | less
drwxr-xr-x root/root         0 2020-09-29 14:16 ./
drwxr-xr-x root/root         0 2020-09-29 14:16 ./boot/
-rw-r--r-- root/root   4285674 2020-09-29 14:16 ./boot/System.map-5.8.11-bone17
-rw-r--r-- root/root    182474 2020-09-29 14:16 ./boot/config-5.8.11-bone17
drwxr-xr-x root/root         0 2020-09-29 14:16 ./boot/dtbs/
drwxr-xr-x root/root         0 2020-09-29 14:16 ./boot/dtbs/5.8.11-bone17/
-rwxr-xr-x root/root     87267 2020-09-29 14:16 ./boot/dtbs/5.8.11-bone17/am335x-abbbi.dtb
-rwxr-xr-x root/root     86826 2020-09-29 14:16 ./boot/dtbs/5.8.11-bone17/am335x-baltos-ir2110.dtb
-rwxr-xr-x root/root     87544 2020-09-29 14:16 ./boot/dtbs/5.8.11-bone17/am335x-baltos-ir3220.dtb

You can see it's putting things in the /boot directory.

Note: You can also look into the other two .deb files and see what they install.

Move the linux-image- file to your Bone.

host$ scp  linux-image-5.10.168-ti-r74_1xross_armhf.deb bone:.

Hint: You might have to add -P<port> if you changed your port number. You might have to use debian@192.168.7.2 for bone if you haven't set everything up.

Now ssh to the bone.

host$ ssh bone
bone$ ls
bin  exercises linux-image-5.10.168-ti-r74_1xross_armhf.deb

Now install it.

bone$ sudo dpkg --install linux-image-5.8.11-bone17_1xross_armhf.deb

Wait a while. Once done check /boot.

bone$ ls -sh /boot
total 70M
4.0K SOC.sh                      188K config-5.10.168-ti-r74      4.0K uboot
4.6M System.map-5.10.168-ti-r72  4.0K dtbs                         11M vmlinuz-5.10.168-ti-r72
4.6M System.map-5.10.168-ti-r73  7.5M initrd.img-5.10.168-ti-r72   11M vmlinuz-5.10.168-ti-r73
4.6M System.map-5.10.168-ti-r74  7.8M initrd.img-5.10.168-ti-r73   11M vmlinuz-5.10.168-ti-r74
188K config-5.10.168-ti-r72      7.8M initrd.img-5.10.168-ti-r74
188K config-5.10.168-ti-r73      4.0K uEnv.txt

You see the new kernel files. Check uEnv.txt.

bone$ head /boot/uEnv.txt
#Docs: http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0
uname_r=5.10.168-ti-r73
# uname_r=5.10.168-ti-r74

I added the commented out uname_r line to make it easy to switch between versions of the kernel.

Reboot and test out the new kernel.

bone$ sudo reboot

Copying to SD card on a running Bone - build_kernel.sh

You can stop here if you've just finished the build_deb.sh method of installing the kernel.

The Bone can have multiple versions of the kernel installed on it. It's possible to update the kernel on the Bone while it's running. After compiling on the host you need to install sshfs (you only need to do this once).

host$ sudo apt install sshfs 

Then copy may_install_kernel.sh to the bb-kernel directory.

host$ cd ~/BeagleBoard/bb-kernel
host$ cp ~/BeagleBoard/exercises/linux/kernel/may_install_kernel.sh tools

Now you can install the files using the following. Note, you must run may_install_kernel.sh from the directory above as shown.

host$ tools/may_install_kernel.sh
Mounting sshfs
-----------------------------
sshfs mounted
Installing 4.4.15-bone11 to sshfs
‘/home/yoder/BeagleBoard/bb-kernel/deploy/4.4.15-bone11.zImage’ -> ‘/home/yoder/BeagleBoard/bb-kernel/deploy/disk/zImage’
Installing 4.4.15-bone11-dtbs.tar.gz to sshfs
Installing 4.4.15-bone11 to sshfs
‘/home/yoder/BeagleBoard/bb-kernel/deploy/4.4.15-bone11.zImage’ -> ‘/home/yoder/BeagleBoard/bb-kernel/deploy/disk/boot/vmlinuz-4.4.15-bone11’
Installing 4.4.15-bone11-dtbs.tar.gz to sshfs
info: /boot/uEnv.txt: uname_r=4.4.15-bone11
Installing 4.4.15-bone11-modules.tar.gz to sshfs
tar: ./lib/modules/4.4.15-bone11/build: Cannot utime: No such file or directory
tar: ./lib/modules/4.4.15-bone11/source: Cannot utime: No such file or directory
tar: Exiting with failure status due to previous errors
‘/home/yoder/BeagleBoard/bb-kernel/deploy/config-4.4.15-bone11’ -> ‘/home/yoder/BeagleBoard/bb-kernel/deploy/disk/boot/config-4.4.15-bone11’
info: [4.4.15-bone11] now installed...

You may see about couple of error messages about build and source, but it seems to work anyway. If you look in /boot/uEvt.txt, you'll see it's ready to boot your new kernel.

bone$ head -3 /boot/uEnv.txt
#Docs: http://elinux.org/Beagleboard:U-boot_partitioning_layout_2.0

uname_r=4.4.15-bone11

If you change your mind about which kernel to boot, just edit the uname line.

Copying to the SD Card on Host - build_kernel.sh

You can also install the kernel on an SD card that is mounted on your host computer. Plug it into your host and machine and run:

host$ tools/install_kernel.sh

This works like the may_install_kernel.sh, but it copies it to local host. Once copied, eject the SD card and plug it into your Bone and boot.

Updating to a new version of the kernel

When you build your kernel the uImage file has some version information in the name. For example vmlinuz-4.4.21-ti-r47. The 4.4.21 is the version of the kernel and the -ti-r47 is the version of the patches applied to the kernel for the BeagleBone. Over time new patches will be posted. These instructions show how to get the latest version.

How do you know if you have the latest version? Run

bone$ uname -a
Linux yoder-debian-bone 4.4.21-ti-r47 #1 SMP Fri Sep 23 22:23:02 UTC 2016 armv7l GNU/Linux

This post to the Google Group lists the steps as "You need to recheckout master, delete your old branch and re-pull". Here's how you do it.

host$ cd linux-dev
host$ git checkout master
error: Your local changes to the following files would be overwritten by checkout:
	patches/defconfig
Please, commit your changes or stash them before you can switch branches.
Aborting

Hmm.... something has changed. See what it is.

host$ git diff patches/defconfig
diff --git a/patches/defconfig b/patches/defconfig
index d903776..3268287 100644
--- a/patches/defconfig
+++ b/patches/defconfig
@@ -2041,6 +2041,7 @@ CONFIG_JHD629_I2C=y
 # CONFIG_SERIAL_NONSTANDARD is not set
 # CONFIG_N_GSM is not set
 # CONFIG_TRACE_SINK is not set
+CONFIG_LPD8806=m
 CONFIG_DEVKMEM=y
 
 #

It looks like some configuration setting have changed. Since we are getting a new version of the kernel, let's revert back to the previous file and try again.

host$ git checkout patches/defconfig
host$ git checkout master
Switched to branch 'master'

Success, now step 2.

host$ git branch -d am33x-v3.8
warning: deleting branch 'am33x-v3.8' that has been merged to
         'refs/remotes/origin/am33x-v3.8', but not yet merged to HEAD.
Deleted branch am33x-v3.8 (was 3fc8a73).

Now repull

host$ git pull

Then start over again

host$ git checkout origin/am33x-v3.8 -b am33x-v3.8
Branch am33x-v3.8 set up to track remote branch am33x-v3.8 from origin.
Switched to a new branch 'am33x-v3.8'

Your system.sh file should be unchanged, so start building

host$ ./build_kernel.sh

Mine took some 26 minutes on an 8 core machine.

Recovering

If your Beagle fails to boot, follow the EBC_Exercise_22_Recovering instructions to recover.




thumb‎ Embedded Linux Class by Mark A. Yoder