The document provides guidance on troubleshooting Linux systems. It discusses preparing for troubleshooting by backing up data and documentation. When issues arise, it recommends gathering information from logs, researching if the problem is widespread, and considering likely causes such as user error, software/hardware issues, or network problems. It then offers solutions such as software and hardware remedies, and provides tips for troubleshooting specific components like applications, networks, disks, and packages.

1. Troubleshooting Linux Keith Wright Technical Training Resources, Inc.

2. Troubleshooting Be prepared! What's the problem? What does the problem affect? What or who is to blame? Searching for solutions Solving the problem or not! What's next?

3. Be Prepared Documentation Back it up! Software Back up any important data Have a regular schedule Automate Backup configuration changes Prepare rescue media Hardware Have spare parts available Have spare machines Use Virtualization/Clustering

4. What's the problem? Gather Information User gnome-screenshot –interactive Run from terminal Log files (/var/log) /usr/bin/gnome-system-log history strace/ltrace top, ps, sar, iostat, vmstat tcpdump, wireshark, ntop, snort Debugging Options

5. How widespread is problem? Research Try other systems If identical systems work diff configuration files Use alternatives Other versions Other software Other architectures Build from source Submit/Fix a bug Network Version Architecture Machine Everyone Software

6. What are likely causes? User error Software configuration changes Missing dependencies Updates to software Updates to hardware Hardware problems Updates to network Network problems

7. Quick Fixes Software Reboot Reinstall software add-apt-repository (/etc/apt/sources.list) Update (apt-get update;apt-get upgrade –f) Hardware -> System, Administration, Hardware Drivers System, Administration, System Testing Shutdown and Boot Check cables, connections, indicator lights, and power Ubuntu: Recovery Mode Clean, dpkg, grub, netroot, root

8. Troubleshooting Boot grub legacy: /boot/grub/menu.lst grub 2: /boot/grub/grub.cfg startupmanager package Recovery Mode Append kernel arguments 1 (Single user mode) emergency (Just a shell) linux rescue (Get rescue distro CD or...) package: grub-rescue-pc mount /dev/rootpartition /target dpkg --root /target --install package.deb sysv-rc-conf or rcconf to manage daemons /etc/default/* for startup parameters /etc/init.d/* for daemon scripts /etc/init/* for system initialization scripts

9. Troubleshooting X11 gnome-display-properties ~/.config/monitors.xml ~/.gconfd/saved_state ~/Xclients-default /etc/X11/xorg.conf /var/log/Xorg.0.log CTRL+ALT+BACKSPACE ATI & Nvidia drivers System, Administration, Hardware Drivers Need to build kernel module build-essential linux-headers-$(uname –r)

10. GNOME Desktop Problems gconf-editor /apps/panel/global/locked_down /desktop/gnome/lockdown rm -rf ~/.gconf ~/.gconfd ~/.gnome2 ~/.gnome2_private

11. Troubleshooting Processes ps -ef | grep foo pkill (-9) foo, pkill -u user kill -9 pid xkill top, htop, atop, gnome-system-monitor latencytop, powertop

12. GUI Applications Is a dialog box displayed? Press the PrintScr key on the keyboard and save the message Save the file for reference or being able to share it with others Run Application from Terminal Right-click the menu item, select Add this laucher to the desktop Right-click the item on the desktop, select Properties, and copy the command Open a Terminal and execute the command Look for informative error messages

13. Application crashes Open a terminal Read the manual and start the Application in a debugging mode Perform operation that caused crash Analyze any error messages Save output Research error message

14. Command Not Found or not working as expected Was the command typed correctly? Is the file executable to the user Is the file located on the user's PATH? Echo $PATH Export PATH=/foo/bar:$PATH Is the executing the correct one? which echo type echo alias

15. Troubleshooting Ethernet Using networking or network-manager services ifconfig, ip route, traceroute, mtr Configuration Files: /etc/network/interfaces (Ubuntu) /etc/resolv.conf /etc/hosts

16. Troubleshooting Wireless Know your kernel: uname -r Know your hardware: dmesg, lspci -v, lsusb -v, /etc/modules Know your configuration: ifconfig, iwconfig, nm-tool, iwlist wlan0 scan System, Preferences, Network Connections http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wireless.html

17. NetworkManager If you use NetworkManager, then you don't use the networking service. nm-applet runs in notification area No longer need to login to activate connections nm-tool provides useful information Right click, Edit Connections sudo restart network-manager

18. Troubleshooting Hardware Swap it! OS then parts dmesg lspci -v lsusb lshal /proc cpuinfo meminfo

19. Troubleshooting Disks fdisk -l blkid df -h, du -sh mount /etc/fstab fuser -v foo.bar lsof (-u user) (-p pid) smartctl -a /dev/sda

20. Disk Recovery Tools testdisk recovers partitions and deleted files foremost recovers specific file types that are deleted

21. Troubleshooting Help Search for exact error message Research RTFM, info and doc Use community forums Use mailing lists help.ubuntu.com ubuntuforums.org linuxquestions.org freenode.net

22. References http://delicious.com/keithwright/scalets http://help.ubuntu.com http://ubuntuforums.org/ http://forums.fedoraforum.org/ http://tldp.org/ http://www.linuxtroubleshooting.com/ Irc freenode.net #rhel #fedora #ubuntu

23. Building Debian Packages Debian souce code packages are distributed in .dsc files. To build any Debian package, the build environment must be installed through the metapackage build-essential. # apt-get install build-essential For each specific package foo, then: # apt-get build-dep foo # apt-get source --build foo Then create a dedicated version of your own build dch -l local 'Blah blah blah' debuild -us -uc Install your package by running sudo dpkg -i ../*.deb

24. Using the dpkg command To enable logging of commands use the --log option List all packages: dpkg -l To query an individual package: dpkg --status package Viewing package status: dpkg --get-selections \* > selections.txt Setting package status: dpkg --set-selections <selections.txt Installing a package: dpkg --install package.deb Unpack a package: dpkg --unpack package.deb Configure a package: dpkg --configure package Remove a package (but not configs): dpkg --remove package Purge all package files: dpkg --purge package List files in a package: dpkg --listfiles package Find package providing file: dpkg --search filename To find a package to provide a file: apt-file search filename

25. apt-get - To install, update, remove, or purge packages Repositories configured with /etc/apt/sources.list Update list of available packages: apt-get update Install updated packages without adding/removing: apt-get upgrade Install all updated packages: apt-get dist-upgrade Install a specific package: apt-get install package Remove a package: apt-get remove package Purge a package: apt-get --purge remove package The cron-apt package creates a cron job to automatically update

26. apt-cache - To query packages To search for a keyword: apt-cache search keyword To query information: apt-cache show package To determine dependencies: apt-cache depends package To show detailed information about all versions of a package and its dependencies: apt-cache showpkg package

27. Troubleshooting Packages Try creating a new user and running the application. If it works for the new user, but not the old one, then old configuration files may be the problem. Move the old user's dot files and retry. If one package overwrites (conflicts) with another packages files, then remove one of the packages. If install or remove scripts for a package fail, then correct the problem in: /var/lib/dpkg/packagename.scriptname file. Then use: dpkg --configure –a apt-get update; apt-get upgrade -f

28. Package Management Frontends aptitude - works CLI and well as an text application - tracks dependencies and removes them when not needed dselect - works as a menu driven text application synaptic - GUI application software-center - GUI application appearing on Applications menu