Generating the SDK Image

For a regular SDK image

bitbake -c populate_sdk <image_name>

For the eSDK image:

bitbake -c populate_sdk_ext <image_name>

Installing the eSDK Image

Must have Python installed. An additional gotcha, the script checks for Python using which, so naturally, which must also be installed. The SDK also cannot be installed as root.

Setting up SSTATE_MIRRORS

Must add the SSTATE_MIRRORS entry after SDK installation, manually. This goes in poky_sdk/conf/local.conf. Remember that this variable is formatted in pairs: the first is a regexp to select the files from the server URL provided in the second argument. Assuming that when I navigate to http://edtwardy-yocto.local/sstate-cache/ in my browser, I'm met with a directory index that contains many numbered subdirectories (the sstate-cache), the following entry will work for me:

SSTATE_MIRRORS = "\
...
file://(.*) http://edtwardy-yocto.local/sstate-cache/\1 \
"

Installing Extra Packages with the eSDK

The packages must first be built, server-side, otherwise attempting sdk-install will result an error like:

ERROR: Failed to install cargo-native - unavailable

Otherwise, the following will generally work:

devtool sdk-install <packageName>

Static Library Packages

Host Tools

Creating a package that generates a host tool is exceedingly easy--just add the following to the recipe:

BBCLASSEXTEND = "native nativesdk"

Adding these lines creates two new recipes in the layer, in addition to <pkgname>--<pkgname>-native and nativesdk-<pkgname>. To depend on this devtool, just add <pkgname>-native to your DEPENDS:append specification in your reliant recipe.

Theoretically, the nativesdk-<pkgname> recipe is installable via an Extensible SDK, but I haven't figured that out yet.

devshell Tricks

Faux Scrolling

The terminal emulator used with the devshell is Tmux. To enable faux scrolling in Tmux, press Ctrl-b + : to enter a command, and run the command setw mouse on.

Clangd

If compiling using a GCC compiler, we should only need to tell clangd about which compilers to query when a non-clang compiler is encountered in the command field of an entry in compiler_commands.json:

export CLANGD_FLAGS="--query-driver=$(dirname $(which $CC))/*"

# Now generate the compiler database using your build system, e.g. for ninja:
ninja -C oe-workdir/recipe-1+git9999 -t compdb

From within a devshell, the CLANGD_FLAGS environment variable should expand to a glob expression that clangd will match compilers against. Clangd will automatically get the system include flags from the matching compiler.

Generating a List of Packages

bitbake -g <image> && cat pn-buildlist | grep -ve "native" | sort | uniq

Figuring Out Why a Recipe is Built

$ bitbake -g core-image-minimal
$ oe-depends-dot -k busybox -w ./task-depends.dot

Extracting an initramfs from a kernel image

Given a kernel image in bzImage format, the initramfs is stored as a gzipped CPIO archive in an ELF section. Extract the kernel ELF image from the bzImage, extract the initramfs image, and unarchive its contents:

$ binwalk --extract bzImage-initramfs-gadget.bin
$ readelf -S _bzImage-initramfs-gadget.bin.extracted/42C4
    ...
  [16] .init.data        PROGBITS         ffffffff82cfe000  01efe000
       0000000000816378  0000000000000000  WA       0     0     8192
    ...
$ objcopy -O binary --only-section=.init.data \
  _bzImage-initramfs-gadget.bin.extracted/42C4 initramfs.cpio.gz
$ cpio -i -d -H newc --no-absolute-filenames <initramfs.cpio.gz