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Crash dump anaylsis

Here is how to analyze a kernel crash dump in CentOs

First, to install vmlinux with debugging symbols

strings /var/crash/127.0.0.1-2013-06-22-18\:15\:01/vmcore | less

Look for the kernel version. In this case:

OSRELEASE=2.6.32-220.el6.x86_64

Go to

http://debuginfo.centos.org/6/x86_64/ and download
kernel-debuginfo-2.6.32-220.el6.x86_64.rpm  and
kernel-debuginfo-common-x86_64-2.6.32-220.el6.x86_64.rpm

Install on target machine with

rpm -ivh kernel-debuginfo-common-x86_64-2.6.32-220.el6.x86_64.rpm
rpm -ivh kernel-debuginfo-2.6.32-220.el6.x86_64.rpm

Finally, the crash dump analysis:

  crash /usr/lib/debug/lib/modules/2.6.32-220.el6.x86_64/vmlinux ./vmcore


Use the “bt” command to pull up a backtrace. It will tell you what program was running and what happened to cause the crash.

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robocopy hints

rem robocopy options
rem /dst ::daylight savings time adjustment
rem /R:20 :: retry 20 times (30 seconds between tries)
rem /e    :: copy subdirectories including empties.
rem /XO :: exclude older files
rem /mov (remove from source) used for removing from ds1.
rem /purge remove dest files no longer in source


rem debugging
rem /L to test the command
rem /LOG:file :: log to file
rem /TEE      :: file and console output
rem /V        :: verbose.
rem /np       :: Don't show percentage copied

robocopy g:/source h:/dest /log:g:/source-copy.log /tee /dst /e /r:20 /xo /np

Dircolors

dircolors is something I would like to hate. It is so nice, though. I found some handy workarounds if you find yourself straining to see some of the colors because you, perhaps, opted for a light background color.

There are a few ways to go about this depending on your flavor of system.

First, you will need the existence of a light background dircolor file. Many times this can be found as /etc/DIR_COLORS.lightbgcolor .

One way to get this to work is to set an environment variable

eval `dircolors /etc/DIR_COLORS.lightbgcolor`

Another way to get the behavior, on some flavors of *nix, is to link this file to a dot file in your home directory.

ln -s /etc/DIR_COLORS.lightbgcolor ~/.dir_colors

Resetting file permissions

One of the worst things about NTFS as far as I am concerned is forcing permissions on removable media, when those permissions can so easily be overridden. Here is how to reset the permissions on removable media from windows 7.

  • start up cmd as administrator
  • takeown /f d:\path /r
  • icacls d:\path /reset /T

d:\path is the drive and path to the file or directory you want to reset.

Those attending fart class always try fo

Those attending fart class always try for a passing grade. #joke

ssh speed up

Here is a new one. When ssh slows down put

GSSAPIAuthentication no

into /etc/ssh/ssh_config

 

 

Rescan a scsi bus

Here is the REALLY CRYPTIC way to re-scan a scsi bus in Linux.

echo "- - -" > /sys/class/scsi_host/host0/scan

Have fun with that one.