Crucial Paradigm

If you are getting an error something along this lines of the following:

-bash-3.2# sh ./latest
Creating directory installd
Verifying archive integrity… All good.
Uncompressing cplyr1-cPanel………………………………………………………………………………………………..
____ _
___| _ \ __ _ _ __ ___| |
/ __| |_) / _` | ‘_ \ / _ \ |
| (__| __/ (_| | | | | __/ |
\___|_| \__,_|_| |_|\___|_|

Installer Version 11.25.0 r176

Ensuring system time is set
Updated system time from rdate.cpanel.net: Fri Mar 12 04:54:26 UTC 2010
Verified directory /scripts exists.
Verified directory /scripts/cPScript exists.
Verified directory /usr/local/cpanel exists.
Verified directory /usr/local/cpanel/logs exists.
Verified directory /usr/local/cpanel/Cpanel exists.
Verified directory /var/cpanel exists.
cPanel configuration /var/cpanel/cpanel.config already exists.
Syncing /scripts
Unable to sync: $! at ./updatenow line 38.
Done syncing /scripts
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
FATAL! Failed to properly update /scripts
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
-bash-3.2#

Make sure you have install rsync, and perl. You can do this by doing:

yum install rsync perl -y

On some of our older servers we have an issue where the official memtest CD does not boot while using IPMI (virtual CD drive). Upon looking for a work around we found 2 options to allow memtest to run even if it did not boot from the official ISO. The first option is RIPLinux 9.3 (we prefer the non-X version), just boot the CD and select the Memory Test option.

The second option is UBCD5 (in beta currently, v4 did not work over IPMI), just start the CD, select the Memory menu and select which version of Memtest you wish to use.

UBCD5 comes with the latest version (4) of memtest, while RIPLinux comes with v2.

In an effort to try and cut down the manual labour in burning in new hardware, we have been working with RIP linux on a USB key.  The idea is to fully automate a read and write to all drives in the system, and then automatically run memtest.  This way we can just plug the USB key into the system, start the script and it will perform and record the burn in tests to the USB key which we can review after a few days (burn in tests can take up to a few days  depending on the hardware!).

To do this we needed to modify the boot menu on the RIPLinux USB key, and set memtest to start automatically after 10 seconds of no input.    This can be done by doing the following:

Under:
LABEL Boot Memory Tester!

Enter:
MENU DEFAULT

Under:
DEFAULT menu.c32

Enter:
TIMEOUT 100

A script can then placed to run automatically run when RIPLinux boots into the standard kernel.  The script will complete the hard drive tests, then it will reboot the server automatically and the memtest will run.

How many times have you logged into a server, and need to find out which exact version of the operating system you are running (Linux).

These commands will give you some details:

lsb_release -a
uname -a
cat * /etc/*release*

Question: How do I monitor all traffic on a Linux host, or for a particular port?

Answer: You can use the application tcpdump, here are some examples:

Monitor a particular interface:

tcpdump -i eth0

Monitor a particular port:

tcpdump -i eth0 ‘port 9996′

Found an interesting article here regarding Youtube’s hosting architecture. Quite simple actually: http://highscalability.com/youtube-architecture

Youtube has over 1billion views per day, so quite impressive setup!

Rather than building from source, there is a much quicker way of installing ntop on CentOS 5 or RHEL. You can do it via yum! Just add the following file: /etc/yum.repos.d/dag.repo:

[dag]
name=Dag RPM Repository for Red Hat Enterprise Linux
baseurl=http://apt.sw.be/redhat/el$releasever/en/$basearch/dag
gpgcheck=1
gpgkey=http://dag.wieers.com/rpm/packages/RPM-GPG-KEY.dag.txt
enabled=1

Then just run:

yum install ntop -y

If you receive this error while trying to install ntop:

configure: error: cannot find macro directory `m4′

Try creating the directory m4 in the ntop installation directory:

mkdir m4

Rather than building from source, there is a much quicker way of installing rrdtool on CentOS 5 or RHEL. You can do it via yum! Just add the following file: /etc/yum.repos.d/dag.repo:

[dag]
name=Dag RPM Repository for Red Hat Enterprise Linux
baseurl=http://apt.sw.be/redhat/el$releasever/en/$basearch/dag
gpgcheck=1
gpgkey=http://dag.wieers.com/rpm/packages/RPM-GPG-KEY.dag.txt
enabled=1

Then just run:

yum install rrdtool

Have you encountered the following error while trying to compile applications from source on your VPS or server?

-bash: ./configure: No such file or directory

To fix this on CentOS, just install make:

yum install make