Resources for “A Server (Almost) of Your Own”
Some of the code was formatted incorrectly in George Belotsky's “A Server (Almost) of Your Own” in our December 2006 issue. For the corrected version of the article, please see: /article/8337
This page contains updates to the article, as well as some important security information for running your VPS.
Thanks again to Sean Reifschneider, Evelyn Mitchell and the rest of the Tummy.com crew for their very helpful suggestions and for letting me use their equipment once more, to test the updates presented here.
While you can still get a VPS based on Fedora Core 3, the system used for the article, you may want something more recent. For example, CentOS 4.4, which derives from Red Hat Enterprise Linux, requires only minor deviations from the directions in the article text. The CentOS project home page is at www.centos.org.
The following notes update the instructions from Fedora Core 3 to CentOS 4.4. Tummy.com offers both variants, as well as several others, including Ubuntu and Debian.
When you configure the firewall with system-config-securitylevel-tui, the text-based GUI may not render correctly in your terminal. If this makes it difficult to use the application, try running the terminal program with the UTF-8 character encoding.
For example, xterm -u8 should launch a UTF-8 xterm. In gnome-terminal, select Terminal→Set Character Encoding→Unicode (UTF-8) from the menu bar in order to enable UTF-8.
You will need to update the last two lines of Listing 1, as the Postfix mail server version has changed. Here is the new code.
sample_directory = /usr/share/doc/postfix-2.2.10/samples readme_directory = /usr/share/doc/postfix-2.2.10/README_FILES
Note that the sample_directory parameter is obsolete since version 2.1 of Postfix.
When testing your mail server by telnetting to port 25, you may find it blocked by your local ISP. Many DSL and cable providers do this now.
It is quite simple to configure Postfix so it listens on a non-standard port, such as 10025, in addition to port 25. Edit the file /etc/postfix/master.cf. Note that this is not the main.cf file that you worked with in Listing 1. Near the top, you will find the following lines:
# ======================================================================= # service type private unpriv chroot wakeup maxproc command + args # (yes) (yes) (yes) (never) (100) # ======================================================================= smtp inet n - n - - smtpd
Add the following line, after the “smtp” line.
10025 inet n - n - - smtpd
Next, restart Postfix: /etc/init.d/postfix restart.
Finally, re-run the system-config-securitylevel-tui utility as described in the article. On the “Customize” screen, add 10025 to the “Other ports” text box. If there are other entries in this textbox, scroll to the last one, add a space, and make the new, additional entry. “OK” your changes and restart iptables, as discussed in the article.
From your workstation, you can now telnet to port 10025 on your VPS instead of port 25, to carry out the tests described in the article. After sending these hand-generated test messages, remember to check the Spam folder at the receiving end. Unusual formatting, such as the lack of a subject, of these e-mail messages may cause them to be flagged as junk.
While on the subject of spam, the problem is getting worse, as you probably know. Listing 1 in the article uses luser_relay to deliver mail for unknown recipients to a specific user on the system. This is very convenient, because you can just invent e-mail addresses, and they will work without any configuration changes.
Unfortunately, luser_relay may expose you to a lot more spam. If this happens, you will need to add all your legitimate addresses to /etc/aliases and comment out luser_relay. The article text describes how to work with /etc/aliases.
When setting up Dovecot to provide POP3 and IMAP service, the newer configuration file may look a little different.
In CentOS 4.4, the default configuration has the protocols line commented out. It is also changed from what appears in the article text:
#protocols = imap imaps
Do not be confused by these minor differences; just add the code as described in the article: protocols = pop3 imap in this case. Dovecot will still work correctly.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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- SUSE LLC's SUSE Manager
- My +1 Sword of Productivity
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- Non-Linux FOSS: Caffeine!
- Managing Linux Using Puppet
- Doing for User Space What We Did for Kernel Space
- Tech Tip: Really Simple HTTP Server with Python
- Parsing an RSS News Feed with a Bash Script
- SuperTuxKart 0.9.2 Released
- Google's SwiftShader Released
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide