A chronological documentation test project, nothing serious, really!

18 Sep 2008 2-sided print of Redhat manuals using Acrobat

This is a short note on how I have configured Adobe Acrobat to print out 2-sided Redhat manuals described in my previous post using a Canon iR C2880 printer. This gives me 4 pages of manuals in one sheet, and thats quite nice considering the fact that the Redhat Enterprise Linux Deployment Guide is 978 pages.

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18 Sep 2008 Redhat documentation in one place is a documentation page I always return to when I manage Redhat Enterprise Linux systems.

Redhat has put a lot of effort in their documentation and even allow you to download them as PDF documents.

The documentation below is for RHEL5.2

Deployment Guide May 21, 2008 PDF
Installation Guide May 21, 2008 PDF
Virtualization Guide May 21, 2008 PDF
Cluster Suite Overview May 21, 2008 PDF
Cluster Administration May 21, 2008 PDF
LVM Administrator’s Guide May 21, 2008 PDF
Global File System May 21, 2008 PDF
Using GNBD with GFS May 21, 2008 PDF
Linux Virtual Server Administration May 21, 2008 PDF
Using Device-Mapper Multipath May 21, 2008 PDF
Tuning and Optimizing Red Hat Enterprise Linux for Oracle 9i and 10g Databases Nov 2007 PDF
Online Storage Reconfiguration Guide (Beta) July 2, 2008 PDF

These documents is a great resource if you plan to become a RHCT or RHCE.

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17 Sep 2008 Disable IPv6 on Redhat RHEL4

First you remove this line from /etc/modprobe.conf if this line exists.

alias net-pf-10 ipv6

Add the following line to /etc/modprobe.conf

alias net-pf-10 off

Reboot the system. IPv6 is now disabled.

To re-enable IPv6, remove the alias net-pf-10 off line from /etc/modprobe.conf and reboot the machine.

I’ve also made a post about how to disable IPv6 on RHEL5.

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17 Sep 2008 Listen to network traffic using tcpdump

Please note that you have to be the root user to use this command because it puts the network card in promiscuous mode.

# tcpdump -i eth0 -A -s 0 udp port 1514 and host

The example above command listens on port 1514 which is the port ossec-hids uses on its secure communication between server/agent.

-i Listen on interface.
-A Print each packet (minus its link level header) in ASCII.
-s Snarf snaplen bytes of data from each packet rather than the default of 68 (with SunOS’s NIT, the minimum is actually 96). Setting snaplen to 0 means use the required length to catch whole packets.
udp - listen to UDP traffic
port - the port you want to listen to
host your host IP address


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13 Sep 2008 Enable query caching in mysql

Query caching is a way to increase the performance of mysql by caching database queries.
It’s quite easy to do and only requires to edit one file, in Debian it’s called /etc/mysql/my.cnf

Add the following lines in the mysqld section

query-cache-type = 1
query-cache-size = 10M

restart the mysql daemon

# /etc/init.d/mysql restart

Verify that query caching is enabled

# mysql -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 33499
Server version: 5.0.32-Debian_7etch6-log Debian etch distribution

Type 'help;' or '\h' for help. Type '\c' to clear the buffer.

mysql> SHOW VARIABLES LIKE '%query_cache%';
| Variable_name                | Value    |
| have_query_cache             | YES      |
| query_cache_limit            | 1048576  |
| query_cache_min_res_unit     | 4096     |
| query_cache_size             | 10485760 |
| query_cache_type             | ON       |
| query_cache_wlock_invalidate | OFF      |
6 rows in set (0.00 sec)

If you see something like the out above, caching is enabled.

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