Category Archives: Linux

Building the Linux Kernel on one machine, deploying on another

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Software Development flow is an elusive beast, easily frightened away. The easiest way to lose the flow is to have a long development cycle. Building the entire Linux Kernel takes time. If you are developing a single driver that can be built as a stand alone module, you do not want to have to rebuild the entire Kernel each time you make a change to that module. If that module crashes the machine when it runs into an error, you do not want to have to wait for that machine to reboot before digging in to the debugging process.

These two guidelines lead to a pattern of building on one machine and deploying on another. Here is one way to go about this process.

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Adding stable to a blobless clone

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We regularly sync various git repos from upstream to our company speicfic Linux repository. However, sometimes when working on a development machine, I need a branch from stable that we have not synced yet. If I did a blobless clone from our repository, doing a fetch from stable is going to pull over lots of blobs that I do not need.

Instead, I want to fetch just a specific tag. I can do this by adding the tag to the fetch command, and it will pull over only those blobs

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Building a Custom Fedora Based Kernel with Local Patches

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How can I create a binary kernel RPM that has patches that have not yet merged into the mainline kernel? One approach to building the Kernel RPM is to use the Makefile option provided with the Kernel. While we typically do this, it does not provide us with the user land tools like perf and its libraries used to test certain patches.

An alternative approach is to take the Fedora Kernel Source RPM that matches the targeted upstream Kernel version, and modify it to apply the set of patches. Here is a walk-through of the process I just got to succeed.

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Merging Config Fragments in the Linux Kernel

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If you have a config fragment that you want included in your Linux config file, you can use the make system to add it to the existing config. For example, I have a file called: kernel/configs/ampere-topic-mctp.config that looks like this:

CONFIG_MCTP_TRANSPORT_PCC=m

This tells the make system to change CONFIG_MCTP_TRANSPORT_PCC from the default (=n) to module (=m) when building. To include this config fragment, I append it to the make file command to build the config file. For example:

make olddefconfig  ampere-topic-mctp.config

This can be done with multiple fragments.