This document provides an overview of the basic parts of a Linux system, including the boot loader, kernel, glibc, and init processes. It also covers methods for analyzing and debugging applications, running services, and troubleshooting server issues. Key tools discussed include strace, ltrace, and information about memory and storage management.

1. Diagnostics of a
Linux System
Understanding Your Operating System
Stephan Barth Sander van Vugt
Senior Technical Support Engineer Independent Trainer and Consultant
stephan.barth@novell.com mail@sandervanvugt.nl

2. Overview
A Few Words About Us
Basic Parts of a Linux System (theory)
Analyzing and Debugging
Other Important Tools and Commands
Demo: Troubleshooting Server Issues
2 © Novell, Inc. All rights reserved.

3. Basic Parts of a Linux System

4. Basic Parts of a Linux System
Boot loader, e.g. Grub, LILO
Kernel
glibc
init
4 © Novell, Inc. All rights reserved.

5. Basic Parts of a Linux System
• Monolithic kernel with modules
• Compiled in options and drivers
– zcat /proc/config.gz
• Modules that are being loaded
– lsmod
– dmesg
– /proc and /sys
5 © Novell, Inc. All rights reserved.

6. Basic Parts of a Linux System
• Glibc
– # /lib/libc.so.6
– /etc/ld.so.conf
– /etc/ld.so.cache
– ldconfig
– Timezone
– rpm -q --provides glibc
– ldd and nm
– More info with: info glibc
• Try to compile packages on your own
6 © Novell, Inc. All rights reserved.

7. Basic Parts of a Linux System
• init
• ldd /sbin/init
• /etc/inittab
– initial boot
– runlevels
– tty's
Demo
7 © Novell, Inc. All rights reserved.

8. Understanding Your Operating System
• What happens during boot?
– Kernel start up and initrd
– boot options
– boot.msg
> Examples
– module options
– debug kernel
– MCE
– hal
– lspci, lsusb
8 © Novell, Inc. All rights reserved.

9. Understanding Kernel Loading
from GRUB
• GRUB is the first thing that runs when booting the server
• Responsible for loading kernel and initrd
• root file system is activated as a kernel argument
• Specific options can be loaded from the boot prompt
Demo
9 © Novell, Inc. All rights reserved.

10. Analyzing and Debugging

11. Application Debugging
• ldd $(which gpg)
• rpm -q --requires gpg2
• strace / ltrace
• objdump
• GNU debugger gdb
• Valgrind
• Closed source software
11 © Novell, Inc. All rights reserved.

12. Running Services
strace/ltrace
Increase debug level
Change init script – very last option
12 © Novell, Inc. All rights reserved.

13. Memory and Storage
• Memory debugging is difficult
– ps
– top
– sar
• Disk usage
– df vs. du
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14. Other Important Tools and Commands

15. Miscellaneous Tools
• Parted
• Ethtool
• RPM
– rpm -qf
– rpm -qa --last
– zypper
• How to find files, packages: ARCHIVES.gz, pin, distpin
15 © Novell, Inc. All rights reserved.

16. Looking at Startup
• Different stages in startup
– GRUB
– loading of kernel and initrd
– init taking over and doing initial boot
– init starting runlevels
Demo
16 © Novell, Inc. All rights reserved.

17. Novell Tools ®
supportconfig
Novell Support Advisor
17 © Novell, Inc. All rights reserved.

18. Demo: Troubleshooting Server Issues

20. Unpublished Work of Novell, Inc. All Rights Reserved.
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