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Mastering Embedded Linux Programming

You're reading from   Mastering Embedded Linux Programming Unleash the full potential of Embedded Linux with Linux 4.9 and Yocto Project 2.2 (Morty) Updates

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Product type Paperback
Published in Jun 2017
Publisher Packt
ISBN-13 9781787283282
Length 478 pages
Edition 2nd Edition
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Author (1):
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Mr. Chris Simmonds Mr. Chris Simmonds
Author Profile Icon Mr. Chris Simmonds
Mr. Chris Simmonds
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Table of Contents (17) Chapters Close

Preface 1. Starting Out FREE CHAPTER 2. Learning About Toolchains 3. All About Bootloaders 4. Configuring and Building the Kernel 5. Building a Root Filesystem 6. Selecting a Build System 7. Creating a Storage Strategy 8. Updating Software in the Field 9. Interfacing with Device Drivers 10. Starting Up – The init Program 11. Managing Power 12. Learning About Processes and Threads 13. Managing Memory 14. Debugging with GDB 15. Profiling and Tracing 16. Real-Time Programming

Configuring user accounts

As I have hinted already, it is not good practice to run all programs as root, since if one is compromised by an outside attack, then the whole system is at risk. It is preferable to create unprivileged user accounts and use them where full root is not necessary.

User names are configured in /etc/passwd. There is one line per user, with seven fields of information separated by colons, which are in order:

  • The login name
  • A hash code used to verify the password, or more usually an x to indicate that the password is stored in /etc/shadow
  • The user ID
  • The group ID
  • A comment field, often left blank
  • The user's home directory
  • (Optional) the shell this user will use

Here is a simple example in which we have user root with UID 0, and user daemon with UID 1:

root:x:0:0:root:/root:/bin/sh
daemon:x:1:1:daemon:/usr/sbin:/bin/false

Setting the shell for user daemon...

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