See garnet/bin/guest/README.md for more general information.
Repeat each of the following steps for ARCH=x64 and ARCH=arm64.
Run the script to build Linux:
$ ./garnet/bin/guest/pkg/linux_guest/mklinux.sh -l /tmp/linux/source -o garnet/bin/guest/pkg/linux_guest/images/${ARCH}/Image -b machina-4.18 ${ARCH}
Note: -b specifies the branch of zircon_guest to use. You can modify this value if you need a different version or omit it to use a local version.
Repeat for the sysroot:
$ ./garnet/bin/guest/pkg/linux_guest/mksysroot.sh -r -p garnet/bin/guest/pkg/linux_guest/images/${ARCH}/disk.img -d /tmp/toybox -s /tmp/dash S{ARCH}
Ensure that linux_guest is working correctly. Then upload the images to cipd. Use the git revision hash from zircon-guest.googlesource.com/third_party/ linux as a tag.
cipd create -in garnet/bin/guest/pkg/linux_guest/images/${ARCH} -name fuchsia_internal/linux/linux_guest-<version>-${ARCH}-install-mode copy -tag "git_revision:<git revision>"
Then update garnet/tools/cipd_internal.ensure to point to the new version (with the appropriate git hash).
Create a branch within zircon-guest.googlesource.com/third_party/linux with naming scheme machina-X.XX where X.XX is the kernel version. Make sure to import all the machina defconfig files from the latest branch. Make sure linux_guest works correctly before updating the images as above. Please also update the instructions above, and in bin/guest/README.md, to use the most recent branch.