dcsimg

John R. S. Mascio Archive

Trimming, Scripting, and Cutting
If you're moving a text file from Windows to Linux, and unless your ftp program has a method of converting the Windows text to Unix, the file will have a CONTROL-M (^M) character at the end of each line. In many cases, the control characters don't hurt anything, because CONTROL-M, or carriage return, is treated as white space, and is ignored by many programs. However, some programs, such as the Perl interpreter, are adversely affected.
Hard and Symbolic Links
1. What's the difference between ln and ln -s?
Slicing Up Spam
One popular method for filtering unsolicited commercial email, or spam, is SpamAssassin (http://www.spamassassin.org). SpamAssassin is a rule-based, mail filtering program that identifies spam. By itself, or combined with Razor (http:// razor.sourceforge.net), a collaborative spam-tracking database, SpamAssassin can effectively eliminate spam from your daily doses of email.
Mailing Lists and ‘Odd’ Files
The simplest way to create a mailing list is to edit the mail aliases file itself, located at /etc/aliases. Simply edit the file and add the list. Lists look like my-list: person1,person2,person3.
An Alternative to ssh
Yes, there are simpler, albeit less flexible solutions available. One possibility is zebedee (http://www.winton.org.uk/zebedee). Designed by Neil Winton and based on the Blowfish (http://www.counterpane.com/blowfish.html) encryption algorithm, zebedee is a lighter-weight, secure tunneling application. While zebedee does require a couple of libraries to run, the zebedee package includes the libraries and the install is very simple to perform. The current stable release of zebedee is 2.4.1, and is provided as Linux RPMs and as a Windows install package.
What Time Is It?
Synchronizing the time on all machines on the same network is incredibly useful and very simple. The Network Time Protocol daemon (ntpd) does all of the dirty work for you. If you have DNS configured and are connected to the Internet, you can synchronize with an external NTP master server or you can set up your own local master server and synchronize all of your machines to it. In the latter case, you'll only need to monitor the master system for reasonably accurate time.
Knoppix: A Very Portable Linux
Knoppix (http://www.knoppix.org, pronounced "k-nop-iks") is a CD-ROM-based Linux distribution. What's Knoppix good for? Lots of things, including running a firewall, recovering from a system disaster, building product demos, or just keeping Linux with you wherever you go. If your computer can boot from a CD, you can drop Knoppix into the drive, power up, and get an instant Linux fix. (See the sidebar "Knoppix System Requirements" for minimum system requirements.)
What is VNC?
VNC is short for Virtual Network Computing. First developed by Olivetti Research Laboratory (now called AT&T Laboratories Cambridge), VNC was originally designed to create and manage virtual network computers that could be added or deleted at will. However, what VNC turned into was a remote display system most similar to PC-Anywhere, the remote access application.
Make Your Machines Fit to Print
1. How can I set up a printer under lpd?
Of Firewalls and PC Printing
1.How do you block access to specific ports from unknown hosts and networks?
Just Do Backups
1. I'm too busy to do backups at home. I can rebuild the computer, right?
Hacked!
If you ride a motorcycle, you know that it's not "if you fall down," but "when you fall down." As a rider, you can't prevent the inevitable, but you can learn what to do in a crash, and learn what to do to minimize your own injuries.
Good Passwords, Better Security
1. Why are passwords important? I connect to the Internet only occasionally, so passwords aren't a big deal, right?