{"id":593,"date":"2014-06-25T09:00:21","date_gmt":"2014-06-25T07:00:21","guid":{"rendered":"http:\/\/www.thelins.se\/johan\/blog\/?p=593"},"modified":"2014-06-22T23:14:38","modified_gmt":"2014-06-22T21:14:38","slug":"yocto-part-iii-a-custom-meta-layer","status":"publish","type":"post","link":"https:\/\/www.thelins.se\/johan\/blog\/2014\/06\/yocto-part-iii-a-custom-meta-layer\/","title":{"rendered":"Yocto part III – a custom meta layer"},"content":{"rendered":"

In this part of the series (previous: i<\/a>, ii<\/a>) we will have a look at setting up our own meta layer, so that we can make changes without having to fork the Yocto recipes.<\/p>\n

The easiest way to create a layer is to use the yocto-layer<\/a> tool. To fully understand what a layer consists of, I recommend looking at the instructions for creating a layer manually<\/a> as well. So, long story short:<\/p>\n

cd ..
\nyocto-layer create diet
\n<\/code><\/p>\n

The name, meta-diet, comes from my goal with this series – to create a minimal fast booting image. Only time will tell how well that goes.<\/p>\n

The yocto-layer create command produces an MIT-licensed layer. The MIT license is a weak copyleft, so you can choose to close it. I’ll leave it open for your enjoyment. Also, remember to change the README file. It contains a few references to xxxx and yyyy, which would be you and your project.<\/p>\n

As we don’t want the layer to be a part of the layers provided by the Yocto project, we need to separate it out. To do this, change the directory so that you stand in the meta-diet directory and run:<\/p>\n

git init
\n<\/code><\/p>\n

Now you are free to do what you like. I suggest making a commit of what is there and perhaps add a remote so that you can push your changes somewhere.<\/p>\n

An empty layer is only so much fun, so lets start by adding a recipe for your core-image-minimal, enhanced with systemd-analyze. First, let’s create a directory for the recipe:<\/p>\n

mkdir -p\u00a0recipes-diet\/images
\n<\/code><\/p>\n

In that directory, create the\u00a0diet-image.bb file using your favorite, non-emacs, editor. Put the following code in it. This means that we use the core-image-minimal as base, and add systemd-analyze to what we want to install onto the image.<\/p>\n

require recipes-core\/images\/core-image-minimal.bb
\n<\/code><\/p>\n

IMAGE_INSTALL += \"systemd-analyze\"<\/code><\/p>\n

As copying code from a blog post is boring, I’ve put the layer on github as meta-diet<\/a>. For this installment, use the part-iii tag.<\/p>\n

To build the diet image, change directory to the build directory and edit the conf\/bblayers.conf file. Simply add the new layer to the BBLAYERS variable. Now you can bitbake the new image as simple as:<\/p>\n

bitbake diet-image<\/code><\/p>\n

So, this installment got us nowhere feature wise, but now we have everything in place to start experimenting!<\/p>\n","protected":false},"excerpt":{"rendered":"

In this part of the series (previous: i, ii) we will have a look at setting up our own meta layer, so that we can make changes without having to fork the Yocto recipes. The easiest way to create a layer is to use the yocto-layer tool. To fully understand what a layer consists of, … Continue reading Yocto part III – a custom meta layer<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[9],"tags":[],"class_list":["post-593","post","type-post","status-publish","format-standard","hentry","category-yocto"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/www.thelins.se\/johan\/blog\/wp-json\/wp\/v2\/posts\/593","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.thelins.se\/johan\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.thelins.se\/johan\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.thelins.se\/johan\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.thelins.se\/johan\/blog\/wp-json\/wp\/v2\/comments?post=593"}],"version-history":[{"count":6,"href":"https:\/\/www.thelins.se\/johan\/blog\/wp-json\/wp\/v2\/posts\/593\/revisions"}],"predecessor-version":[{"id":608,"href":"https:\/\/www.thelins.se\/johan\/blog\/wp-json\/wp\/v2\/posts\/593\/revisions\/608"}],"wp:attachment":[{"href":"https:\/\/www.thelins.se\/johan\/blog\/wp-json\/wp\/v2\/media?parent=593"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.thelins.se\/johan\/blog\/wp-json\/wp\/v2\/categories?post=593"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.thelins.se\/johan\/blog\/wp-json\/wp\/v2\/tags?post=593"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}