Bureaucrats, dave_user, Administrators
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→Building Yocto BSP images including the U-Boot, the Linux kernel, and the target root file system
{{ImportantMessage|text=This process requires a lot of hardware resources in terms of disk storage, RAM, and processing power. For this reason, it also is recommended to consider the use of a physical machine. For more details on this topic, please refer to the specific documentation of your kit related to the advanced use of Yocto build system.
}}
{{ImportantMessage|text=The process described in this section makes use of tons of source files retrieved from many different online repositories. '''Any issue preventing Yocto to access these repositories–whose URLs are statically specified in the recipe files–may stop the build process'''.
For instance, from time to time these URLs change over the time. Consequently, the build process can't complete successfully because the URL included in the recipes don't match the actual address anymore.
Another problem that may interrupt the procedure is a temporary interruption of the Internet connection. The following example shows an error message reported by Yocto in such a case:
<pre>
ERROR: Fetcher failure: Fetch command failed with exit code 4, output:
wget: unable to resolve host address 'download.berlios.de'
ERROR: Function failed: Fetcher failure for URL: 'http://download.berlios.de/fetchmail/fetchmail-6.3.26.tar.xz'. Unable to fetch URL from any source.
ERROR: Logfile of failure stored in: /home/dvdk/build-fb/tmp/work/cortexa7hf-vfp-neon-poky-linux-gnueabi/fetchmail/6.3.26-r0/temp/log.do_fetch.28992
ERROR: Task 632 (/home/dvdk/sources/meta-openembedded/meta-networking/recipes-support/fetchmail/fetchmail_6.3.26.bb, do_fetch) failed with exit code '1'
}}
</pre>
As known, Linux needs a root file system to operate: a root file system must contain everything needed to support the Linux system (applications, settings, data, etc.). The root file system is the file system that is contained on the same partition on which the root directory is located. The Linux kernel, at the end of its startup stage, mounts the root file system on the configured root device and finally launches the <code>/sbin/init</code>, the first user space process and "father" of all the other processes.
