- Mastering Embedded Linux Programming
- Table of Contents
- Mastering Embedded Linux Programming
- Credits
- Foreword
- About the Author
- About the Reviewers
- www.PacktPub.com
- Preface
- 1. Starting Out
- 2. Learning About Toolchains
- What is a toolchain?
- Types of toolchain - native versus cross toolchain
- Choosing the C library
- Finding a toolchain
- Anatomy of a toolchain
- Other tools in the toolchain
- Looking at the components of the C library
- Linking with libraries: static and dynamic linking
- The art of cross compiling
- Problems with cross compiling
- Summary
- 3. All About Bootloaders
- 4. Porting and Configuring the Kernel
- 5. Building a Root Filesystem
- What should be in the root filesystem?
- Programs for the root filesystem
- Libraries for the root filesystem
- Device nodes
- The proc and sysfs filesystems
- Kernel modules
- Transfering the root filesystem to the target
- Creating a boot ramdisk
- The init program
- Configuring user accounts
- Starting a daemon process
- A better way of managing device nodes
- Configuring the network
- Creating filesystem images with device tables
- Mounting the root filesystem using NFS
- Using TFTP to load the kernel
- Additional reading
- Summary
- 6. Selecting a Build System
- 7. Creating a Storage Strategy
- Storage options
- Accessing flash memory from the bootloader
- Accessing flash memory from Linux
- Filesystems for flash memory
- Filesystems for NOR and NAND flash memory
- Filesystems for managed flash
- Read-only compressed filesystems
- Temporary filesystems
- Making the root filesystem read-only
- Filesystem choices
- Updating in the field
- Further reading
- Summary
- 8. Introducing Device Drivers
- 9. Starting up - the init Program
- 10. Learning About Processes and Threads
- 11. Managing Memory
- 12. Debugging with GDB
- 13. Profiling and Tracing
- 14. Real-time Programming
- What is real-time?
- Identifying the sources of non-determinism
- Understanding scheduling latency
- Kernel preemption
- The real-time Linux kernel (PREEMPT_RT)
- Threaded interrupt handlers
- Preemptible kernel locks
- Getting the PREEMPT_RT patches
- High resolution timers
- Avoiding page faults in a real-time application
- Interrupt shielding
- Measuring scheduling latencies
- Further reading
- Summary
- Index
The three init programs that you are most likely to encounter in embedded devices are BusyBox init, System V init, and systemd. Buildroot has options to build all three with BusyBox init as the default. The Yocto Project allows you to choose between System V init and systemd, with System V init the default.
The following table gives some metrics to compare the three:
|
BusyBox init |
System V init |
systemd | |
|---|---|---|---|
|
Complexity |
Low |
Medium |
High |
|
Boot-up speed |
Fast |
Slow |
Medium |
|
Required shell |
ash |
ash or bash |
None |
|
Number of executables |
0 |
4 |
50(*) |
|
libc |
Any |
Any |
glibc |
|
Size (MiB) |
0 |
0.1 |
34(*) |
(*) Based on the Buildroot configuration of system.
Broadly speaking, there is an increase in flexibility and complexity as you go from BusyBox init to systemd.
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