- 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
Typically, you would want to run certain background processes at start up. Let's take the log daemon, syslogd, as an example. The purpose of syslogd is to accumulate log messages from other programs, mostly other daemons. Naturally, BusyBox has an applet for that!
Starting the daemon is as simple as adding a line like this to etc/inittab:
::respawn:syslogd -n
respawn means that, if the program terminates, it will be automatically restarted; -n means that it should run as a foreground process. The log is written to /var/log/messages.
Tip
You may also want to start klogd in the same way: klogd sends kernel log messages to syslogd so that they can be logged to permanent storage.
As an aside, I should mention that, in the case of a typical embedded Linux system, writing log files to flash memory is not such a good idea as it will wear it out. I will cover the options for logging in Chapter 7, Creating a Storage Strategy.
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