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Mastering Embedded Linux Programming

Mastering Embedded Linux Programming

By : Chris Simmonds
4.8 (20)
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Mastering Embedded Linux Programming

Mastering Embedded Linux Programming

4.8 (20)
By: Chris Simmonds

Overview of this book

Mastering Embedded Linux Programming takes you through the product cycle and gives you an in-depth description of the components and options that are available at each stage. You will begin by learning about toolchains, bootloaders, the Linux kernel, and how to configure a root filesystem to create a basic working device. You will then learn how to use the two most commonly used build systems, Buildroot and Yocto, to speed up and simplify the development process. Building on this solid base, the next section considers how to make best use of raw NAND/NOR flash memory and managed flash eMMC chips, including mechanisms for increasing the lifetime of the devices and to perform reliable in-field updates. Next, you need to consider what techniques are best suited to writing applications for your device. We will then see how functions are split between processes and the usage of POSIX threads, which have a big impact on the responsiveness and performance of the final device The closing sections look at the techniques available to developers for profiling and tracing applications and kernel code using perf and ftrace.
Table of Contents (16 chapters)
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15
Index

Temporary filesystems


There are always some files that have a short lifetime or which have no significance after a reboot. Many such files are put into /tmp, and so it makes sense to keep these files from reaching permanent storage.

The temporary filesystem, tmpfs, is ideal for this purpose. You can create a temporary RAM-based filesystem by simply mounting tmpfs:

# mount -t tmpfs tmp_files /tmp

As with procfs and sysfs, there is no device node associated with tmpfs so you have to supply a place-keeper string, tmp_files in the preceding example.

The amount of memory used will grow and shrink as files are created and deleted. The default maximum size is half the physical RAM. In most cases, it would be a disaster if tmpfs grew that large, so it is a very good idea to cap it with a -o size parameter. The parameter can be given in bytes, KiB (k), MiB (m), or GiB (g), for example:

mount -t tmpfs -o size=1m tmp_files /tmp

In addition to /tmp, some subdirectories of /var contain volatile data and it...

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