Novell Open Enterprise Server Administrators Handbook SUSE Linux Edition [Electronic resources] نسخه متنی

Troubleshooting

Troubleshooting SLES can be a complex process. The following section contains important log files, procedures, and tools used during the troubleshooting process.

System Log Files

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.

Table 6.7. Important 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.

`/proc` and `/sys` Filesystems

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. Table 6.8 identifies a few important files found in the /proc and /sys filesystems.

Table 6.8. Important Files Found Within `/proc` and `/sys`
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

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:

1.	Boot from the installation media and select Rescue System from the GRUB menu.
2.	When prompted, select an appropriate keyboard map.
3.	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.
4.	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.)
5.	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.
6.	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 Utilities

Troubleshooting Linux-related problems sometimes involves in-depth investigation of the disk, running processes, networking configuration, and countless other topics. Appendix A, "The Most Essential Linux Commands," or the man page for the respective utility.

Novell Open Enterprise Server Administrators Handbook SUSE Linux Edition [Electronic resources] نسخه متنی

فارسی

کردی

العربیه

اردو

Türkçe

Русский

English

Français

کانال فیلم من

تبیان من

فایلهای من

کتابخانه من

پنل پیامکی

وبلاگ من

اینجــــا یک کتابخانه دیجیتالی است

با بیش از 100000 منبع الکترونیکی رایگان به زبان فارسی ، عربی و انگلیسی