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Softpanorama |
May the source be with you, but remember the KISS principle ;-)
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| Recommended Books | Recommended Links | Installation Checklist | Reference | |||
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Humor | Etc |
Troubleshooting SLES can be a complex process. The following section contains important log files, procedures, and tools used during the troubleshooting process.
SLES uses the System Logger (syslog) utility to track events from all running processes. These events are written to log files that can be used for troubleshooting and system analysis. When you're troubleshooting nearly any type of problem on SLES, these log files are the best place to begin. Table 6.7 identifies key log files found on SLES.
| LOG FILE | PURPOSE |
|---|---|
| /var/log/messages | The majority of syslog messages are stored in this file. |
| /var/log/boot.msg | All boot-related messages are written to this file upon system startup. |
| /var/log/YaST2 | This directory contains log files for the operation of YaST and YaST modules. |
| /var/log/cups | CUPS-related log files can be found in this directory. |
| /var/log/mail | Log file for mail-related messages. |
| /var/log/XFree86.0.log | Log file containing messages relating to the XFree86 server. |
| yast2 view_anymsg -or- yast view_anymsg | Command used to launch YaST into the system log monitoring module. (yast2 is the graphical utility, and yast is the command-line version.) |
NOTE
Log files for OES components can normally be located in /var/opt/novell/log.
When you're troubleshooting hardware-related problems, it is often important to determine exactly what view the kernel has of all hardware devices attached to the server. The /proc filesystem is a virtual filesystem that allows an insight into the running kernel. Many kernel configuration values can be analyzed by viewing the appropriate file within the /proc directory structure.
Beginning with the 2.6 kernel, the sysfs filesystem has been added for accessing additional information regarding kernel data structures and attributes. This filesystem is mounted at the /sys directory and can be used to query specific settings of hardware devices recognized by the current kernel. As not all devices have interfaces within the sysfs filesystem, both the /proc and /sys filesystems must be used for low-level device management.
| FILE | PURPOSE |
|---|---|
| /proc/cpuinfo | Contains information regarding all identified CPUs. |
| /proc/interrupts | Contains information regarding allocated interrupts. |
| /proc/ioports | Contains information regarding configured I/O ports. |
| /proc/scsi/ | Directory containing information regarding the SCSI subsystem. Adapter- and device-specific information can usually be located in adapter- specific directories beneath /proc/scsi. |
| /proc/modules | Contains information regarding currently loaded modules. |
| /sys/devices | Directory structure containing a view of all devices recognized by the running kernel. |
| /sys/bus | Directory structure containing a view of all bus-specific devices recognized by the running kernel. |
Rescue mode is a method of running Linux from the installation media rather than a damaged SLES installation. This mode is useful for advanced troubleshooting and disaster recovery when the installed operating environment is failing to start up properly. Rescue mode is accessed by following these steps:
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1.
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Boot from the installation media and select Rescue System from the GRUB
menu.
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2.
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When prompted, select an appropriate keyboard map.
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3.
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At the Rescue Login prompt, enter root.
After pressing Enter, you will be provided with a BASH prompt.
At this point, SLES is actually running off the CD rather than the hard disk. The real root filesystem must now be located and mounted. Use fdisk <root hard disk device> (the hard disk device might be /dev/sda, for example), and then press p to view the partition table of the selected disk. The root filesystem device will have an ID of 83 and a System of "Linux". When you've located it, record the device name of the root filesystem. If you are unsure of the entry that contains the root filesystem, record all possible matches. These potential matches can be checked one at a time. |
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4.
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Mount the root filesystem that was located in the previous step using
the following command:
mount –t reiserfs <root device (e.g. /dev/sda1)> /mnt
(If your filesystem type is not reiserfs, be sure to modify the command line accordingly.) |
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5.
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Change the current directory to /mnt and ensure that the root
filesystem is correctly mounted. If it is, the original root directory
structure should be visible. If this directory is not visible, unmount
the /mnt directory (using umount /mnt) and then go
back to step 3 to try locating the root filesystem device again.
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6.
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Change your root directory from the CD-based SLES to your installed
operating system using the chroot command as follows:
chroot /mnt |
At this point, a new BASH shell has been opened within the filesystem of your SLES installation. Additional troubleshooting (reviewing log files, changing passwords, disabling services, and so on) can all be performed prior to rebooting in normal mode.
Troubleshooting Linux-related problems sometimes involves in-depth investigation of the disk, running processes, networking configuration, and countless other topics. Table 6.9 outlines a small list of utilities often used in the troubleshooting process.
| UTILITY | PURPOSE |
|---|---|
| df | Reports total, used, and available disk space across all mounted filesystems |
| du | Estimates disk space usage by directories |
| free | Displays total, used, and free memory statistics; also reports information on memory buffers and swap space |
| hwinfo | Reports detailed information on known hardware |
| iostat | Reports input/output statistics for block devices |
| KDE System Guard (ksysguard) | Graphical utility used to monitor system load performance |
| lsof | Lists currently open files |
| ltrace | Traces library calls made by a process |
| netstat | Reports network statistics and route information |
| sitar | Comprehensive reporting tool used to generate a report documenting the entire running environment |
| strace | Traces system calls and signals made by a process |
| tcpdump | Used to capture network traffic for later review using a utility such as Ethereal |
| top | Displays running process and various statistics regarding each process (CPU utilization, memory, and so on) |
| vmstat | Reports virtual memory statistics |
| xosview | Graphical utility used to report system statistics such as CPU usage, load average memory usage, and several other parameters |
Using these troubleshooting utilities to track down and resolve issues can be a daunting task. For help with this process, or any technical issue you may face, contact Novell Technical Support (http://www.novell.com/support). For more information on these utilities, see Appendix A, "The Most Essential Linux Commands," or the man page for the respective utility.
Copyright © 1996-2008 by Dr. Nikolai Bezroukov. www.softpanorama.org was created as a service to the UN Sustainable Development Networking Programme (SDNP) in the author free time. Submit comments This document is an industrial compilation designed and created exclusively for educational use and is placed under the copyright of the Open Content License(OPL). Original materials copyright belong to respective owners. Quotes are made for educational purposes only in compliance with the fair use doctrine.
Standard disclaimer: The statements, views and opinions presented on this web page are those of the author and are not endorsed by, nor do they necessarily reflect, the opinions of the author present and former employers, SDNP or any other organization the author may be associated with. We do not warrant the correctness of the information provided or its fitness for any purpose.
Created May 16, 1996; Last modified: November 08, 2008