Linux Scalability
Doing large scale grid work, we regularly press various limits of Linux and other systems. If you’re in a situation where you’re pushing various limits like open file descriptors and network sockets, here is how to ensure that the limits are large enough.

At several points I suggest making changes to the Linux kernel’s configuration by echoing data into the /proc filesystem. This changes are transient and the system will reset to the default values on an reboot. As a result, you’ll want to place these changes somewhere where they will be automatically reapplied on reboot. On many Linux systems, you can use the /etc/rc.d/rc.local script to do this. Depending on your particular configuration, you might also be able to the /etc/sysctl.conf, although you’ll need to check the documentation for sysctl for the correct format.
Continua”How to increase Linux Scalability for Condor”

Data in MySQL is stored in files (or memory) using a variety of different techniques. Each of these techniques employs different storage mechanisms, indexing facilities, locking levels and ultimately provides a range of different functions and capabilities. By choosing a different technique you can gain additional speed or functionality benefits that will improve the overall functionality of your application.

For example, if you work with a large amount of temporary data, you may want to make use of the MEMORY storage engine, which stores all of the table data in memory. Alternatively, you may want a database that supports transactions (to ensure data resilience).

Continua”A Guide about MySQL Storage Engines”

The following is an extremely simplified view of how SSL is
implemented and what part the certificate plays in the entire process.

Continua”Installing a Self Signed SSL certificate on Apache”

If you find that someone has done a recursive chmod or chown on a server, don’t fret. You can set almost everything back to its original permissions and ownership by doing the following:

rpm -qa | xargs rpm –setperms –setugids

Depending on how many packages are installed as well as the speed of your disk I/O, this may take a while to complete.

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At Home I run a Redhat 7.3 liNUX server which currently not have a current subversion RPM
available for Redhat 7.3.

I wanted to use a subversion Server and TortoiseSVN to have a subversion
setup so that I can store Word Documents and Some HTML files that I use
on my site. However, I could not find a suitable RPM for my distribution.

The only thing left to do is build from source.

I Downloaded the source using wget from the Subversion website.

http://subversion.tigris.org/

Continua”### HOW TO BUILD A KICK ASS SUBVERSION SERVER ###”

HOW I UPGRADED MY IMAP SERVER ON PENGUINCARES

So my email server was running an RPM that provided imap service but it was slow.

I figured i can speed up my server if I install a new imap server, I decided to go
with dovecot server so I removed the old rpm file

Release : 10 Build Date: Wed 17 Apr 2002 06:44:15 PM EDT
Install date: Tue 07 Jun 2005 10:57:45 PM EDT Build Host: stripples.devel.redhat.com
Group : System Environment/Daemons Source RPM: imap-2001a-10.src.rpm
Size : 2303900 License: University of Washington Free-Fork License
Packager : Red Hat, Inc.
URL : http://www.washington.edu/imap/
Summary : Server daemons for IMAP and POP network mail protocols.
Description :
The imap package provides server daemons for both the IMAP (Internet
Message Access Protocol) and POP (Post Office Protocol) mail access
protocols. The POP protocol uses a “post office” machine to collect
mail for users and allows users to download their mail to their local
machine for reading. The IMAP protocol allows a user to read mail on a
remote machine without downloading it to their local machine.

Continua”HOW I UPGRADED MY IMAP SERVER ON PENGUINCARES DOVECOT”

Installing Mailscanner ClamAv and Spamassassin

---

Intro

In this article we will see how to install a basic system to avoid your system to spread spam, virus and any type of crap to your users.

Since it is what we use, the machine which we are speaking about is a CentOS 4.0 with BlueQuartz control panel, to be honest, the one provided by Nuonce.net.

Continua”MailScanner with Sendmail setup”

HOWTO: Install fuse + sshfs on CentOS Linux June 8, 2006
Posted by devhen in CentOS, HOWTO, Linux. trackback

UPDATED Dec-19-2006:

NOTE: These instruction are for CentOS 4.

The apt-get method of installing sshfs that I had posted here previously did not work for me. I got this error when trying to mount an ssh drive:

shfsmount: shfs filesystem not supported by the kernel

So, I set out to find a different method of installing sshfs (and fuse, which it requires). One, preferably, that would actually work. Well, I found one. Its not the most elegant solution but its effective.

First, download a copy of the fuse source rpm:

wget http://www.devhen.net/centos/fuse-2.6.0-1.src.rpm

Next, install the source rpm and then build the proper fuse rpm’s from the .spec file:

rpm -ivh fuse-2.6.0-1.src.rpm
rpmbuild -bb /usr/src/redhat/SPECS/fuse.spec

Next, install the rpms that you have built:

cd /usr/src/redhat/RPMS/i386 (replace ‘i386′ with your arch, if necessary)
rpm -Uvh fuse-2.6.0-1.i386.rpm fuse-kernel-2.6.0-1.i386.rpm fuse-libs-2.6.0-1.i386.rpm fuse-devel-2.6.0-1.i386.rpm

Now you can install the sshfs-fuse rpm:

wget http://www.devhen.net/centos/sshfs-fuse-1.6-2.i386.rpm
rpm -ivh sshfs-fuse-1.6-2.i386.rpm

** You can try building the sshfs-fuse rpm from its source package if your not on i386**

Now comes the ugly part… For some reason the system can’t find the fuse module after installing these packages. So, head over to the fuse project homepage and download fuse-2.6.0.tar.gz. Unpack it and then

./configure
make
make install

and you should be in business. As I said, this is not an elegant solution because you are installing fuse from the tar.gz file on top of the fuse rpms. However, it works for me and that’s all that matters right now because I really needed to mount some ssh drives on my workstation. ;)

Mount an ssh drive like so:

sshfs user@remotesystem:/path/you/want/to/mount/ /mnt/mount-point/ -o allow_other

Don’t forget the trailing /’s on both the source folder and the mount point. -o allow_other will give all users access to the mounted drive. Type sshfs -h for a list of all of sshfs’ options.

Using SMTP AUTH and STARTTLS with sendmail

A quick start guide for Red Hat/Fedora Linux

SMTP AUTH allows users to relay mail after successfully
authenticating. This has augmented and even replaced IP address-based access
controls, mainly due to the wide adoption of dynamically allocated IP addresses
and the demands of roaming users. It makes more sense to control relaying at
the user level, regardless of the host or its location on the Internet, but
care must be taken to protect passwords from being sent in the clear.

Although support is maturing, implementation can still be complex. This
guide will help you to configure sendmail to use SMTP AUTH with STARTTLS on Red
Hat/Fedora Linux. Much of the information presented here will also be useful on
other platforms.

Continua”Using SMTP AUTH and STARTTLS with Sendmail”

Index DNSBL: Configuring Sendmail for DNS-Based Blacklisting Modified: 12 Feb 2007

——————————————————————————–

DNSBL: Configuring Sendmail for DNS-Based Blacklisting
By Weldon Whipple

——————————————————————————–

Contents
Introduction
Step 1: Choose Which Blacklist(s) to Use
Step 2: Modify sendmail.cf for Blacklisting
Optional: Enable DNSBL for Designated Users Only
Alternate Disabling Option: Exempt Specified Local Users from Blacklisting
Optional: Customize the Error Message
Optional: Change Default Behavior When Lookups Fail Temporarily
Appendices
Appendix A: Notes on Creating Your Own DNS Blacklist
Appendix B: Enhanced DNS BlackLists
Appendix C: Subscriber-Only Blacklists–mail-abuse.org
Appendix D: Name Server Issues
Afterword
Introduction
These instructions describe how to modify sendmail’s configuration file to enable the dnsbl (DNS Blacklist) feature to block incoming e-mail from IP addresses that are listed on one or more blacklists. These particular blacklists are checked by sendmail during the SMTP conversation, avoiding the generation of the bounce messages that are generated (for example) when SpamAssassin–called from procmail–consults DNS Blacklists. (The configuration of SpamAssassin to consult DNS Blacklists is outside the scope of this document.)

Here is how DNSBLs work:

Continua”DNSBL: Configuring Sendmail for DNS-Based Blacklisting”