APLawrence.com -  Resources for Unix and Linux Systems, Bloggers and the self-employed

Google Earth Street View

Google is now offering a much closer look at our world. Some folks are raising privacy concerns. As a card-carrying ACLU liberal, I'm supposed to be standing shoulder to shoulder with all my brethren in opposition to video surveillance, but I'm not.

Title Last Comment
Unix and Linux startup scripts, Part 1  
- In the beginning, there was "init". If you had a Unix system, you had "init" and it was almost certainly process id 1. -

Unix and Linux startup scripts, Part 2   2009/12/11 TonyLawrence
- The rc.d system is used on NetBSD, FreeBSD and DragonFly (and possibly a few other systems) to launch daemon processes when the system goes multiuser. -

Unix and Linux startup scripts, Part 3  
- We have looked at both System V and BSD methods; until fairly recently that would hav e been the end of the discussion. -

Creating pretty graphs with RRDTOOL   2014/09/03 Varun
- The open source rrdtool project helps you create a graphical view of any statistic collected at regular intervals. -

VMware Networks, Bridged vs. Nat vs. Host   2011/05/19 Firedancerx
- Understanding VMware networking options. By default, VMware works in "bridged" mode - you use the card by attaching a virtual network device to it. -

Symbols and Apes  
- We are masters of abstraction and indirection. Programmers know that perhaps even more than other people; our world is almost all symbols. But all of us, programmers or not, use symbols every day of our lives. We also often use ritual, and rituals often involve symbols - Wikipedia even defines ritual as "a set of actions, performed mainly for their symbolic value..". -

Google Earth Street View   2011/10/14 bchopper
- I'm sorry. The ACLU will probably want their card back, but I just don't see cameras as a privacy problem. -

Cron is not working   2012/08/17 TonyLawrence
- Let's just get this out of the way first: when someone says cron is not working, it almost always is, and they have just misunderstood something basic. -

Finding large files   2010/10/02 wilson
- Where has the space gone? Although it is getting harder and harder to run out of disk space, some of us still manage to do it. -

Office on Terminal Server   2013/03/15 anonymous
- Installing Microsoft Office on terminal server - licensing issues -

OS X file encryption  
- File encryption for Mac OS X. I'm going to look at two methods for encrypting files on Mac OS X. The first is built in, and uses DisK Utilty to create an encrypted disk image. -

mount --bind   2012/01/03 Daniel
- Using Linux 'mount --bind' instead of symbolic links. If the thing you want to link to is a mounted file system, you can use the "--bind" option of mount to create an unbreakable link. -

Recursive chown   2014/02/07 Joe
- 'chown -R' is smarter than you think. I had email this morning from someone using "chown" to fix up permissions on a directory. He had discovered "-R" in the man page but had run into a small problem... That succesfully changed the ownership of the "dot" files, but had an unexpected (to him) side effect: /usr was also changed. -

Enabling Linux telnet   2012/09/05 TonyLawrence
- If you can't use ssh (as you should!), you'll need to find and install a telnet daemon for your Linux distro. -

Backing up Windows machines using rsync and ssh  
- Rsync and SSh aren't just for Unix and Linux: Windows and Mac can use these to backup data. -

Bash in-process regular expressions   2015/02/21 TonyLawrence
- Bash acquired in-process regular expressions in version 3.0, but I never noticed, probably because most of the machines I'm using are Bash 2.05b. -

Understanding PAM   2014/12/09 TonyLawrence
- PAM is the Pluggable Authentication Module, invented by Sun. It's a beautiful concept, but it can be confusing and even intimidating at first. -

Controlling core files (Linux)   2011/11/06 TonyLawrence
- Control Linux core files with ulimit and /proc templates. -

Map network drive, connect as different user to same Server   2011/11/02 anonymous
- How to map an XP network drive more than once even though XP doesn't want you to do that. -

LOD Communications, Inc.
Writing and Compiling C programs on Linux   2012/02/10 TonyLawrence
- Writing and compiling c programs on Linux, common errors for beginners. Most Linux and Unix programs are written in C. When you download source for a project, it will often be C or C++ source code. You don't necessarily need to know a darn thing about C or anything else to compile the source if you aren't changing it. It may be helpful for you to understand a bit if you are having problems with the compile, but even that isn't really necessary. -

Terminal server, Remote Desktop, thin clients and all that  
- No wonder people get confused. Lots of similar or related things, no end of licensing confusion, no end of general confusion. -

Rebuilding failed Linux software RAID   2011/10/26 kuntergunt
- Rebuild crashed Linux raid. Recently I had a hard drive fail. It was part of a Linux software RAID 1 (mirrored drives), so we lost no data, and just needed to replace hardware. However, the raid does requires rebuilding. A hardware array would usually automatically rebuild upon drive replacement, but this needed some help. -

Basic DNS: PTR records and why you care   2015/04/11 TonyLawrence
- A PTR record (sometimes called a "host PTR record") is what lets someone do a "reverse" DNS lookup - that is, they have your IP address and want to know what your host/domain is. -

UNIX Basics-JOB SCHEDULING   2014/06/19 anonymous
- In the UNIX or Linux environment, it is possible to asynchronously execute tasks at any desired time of the day, a feature made possible by the cron clock daemon. -

The Gimp: Making Colors in a GIF Transparent  
- Sometimes when working with an image you want to make a certain color transparent. When working with a gif file this would make a round circle look round on any color background. This is actually very simple once you do it once. Finding the information for this took me a while so I thought I would pass it on to anyone that was interested. -

Lost root password (Linux)   2014/12/22 TonyLawrence
- Let's try to fix your lost root password the easy way first. The first thing to try is to boot to single user mode. -

Monitoring file or directory changes   2013/02/01 anonymous
- Many modern systems provide a way to watch a directory for events but sometimes brute force or trickery is still needed. -

Perl Input   2011/04/08 TonyLawrence
- Perl has wonderful I/O capabilities. I'm only going to cover input here: reading from files or standard input. There are two ways to do that (actually a lot more than two, but this is supposed to be introductory material): you can open a specific file, or you can pass files on the command line and either open them individually or just ignore the whole thing and pretend everything is coming from STDIN. -

Tightvnc, Chicken of the VNC  
- Reviews of TightVNC and Chicken of the VNC. VNC is "Virtual Network Computing" and is a crossplatform method of allowing remote access to desktops. -

Getopt and getopts   2013/06/29 TonyLawrence
- Both "getopt" and getopts are tools to use for processing and validating shell script arguments. They are similar, but not identical. -

Perl Getopt and GetOptions   2013/02/26 TonyLawrence
- Two Perl modules (Getopt and Getoptions::Long) work to extract program flags and arguments much like Getopt and Getopts do for shell programming. The Perl modules, especially GetOptions::Long, are much more powerful and flexible. -

Perl Net::FTP   2013/09/26 TonyLawrence
- Before the wide spread availability of Perl, I would script ftp transfers with .netrc, ksh scripts and other clumsy ways. None of those methods are fun, flexible or easy. On the other hand, Perl's Net::FTP module is all of that. -

Virtual PC for Mac OS X  
- This is a review of an ancient Virtual PC product and is only left here for historical purposes. -

Operating System Concepts  
- Basic OS concepts. The CPU (Central Processing Unit) is the heart of any computer, but the operating system is the brain. Unfortunately, understanding exactly how these things really work can be difficult, because it's fairly hard to "play" with the operating system that you are actually using. You can do quite a bit with sophisticated debuggers, but eventually you run into confusion and difficulty. And, as you try more complex tasks, you run the risk of interfering with the real machine's operating system. Finally, modern CPU's are very complex, and that complexity can make it more difficult to understand basic concepts. -

Apt-get for RedHat Linux   2011/11/08 TonyLawrence
- RedHat 7.3 and 8.0 do not have tools like Mandrakes urpmi for installing/updating rpms. After researching on Google groups for a similiar Redhat tool . APT seemed to be the best. I think its a tool from Debian linux. -

Linux|Unix Logical Volume Manager (LVM) on Software RAID   2011/01/07 TonyLawrence
- Logical Volume Manager is now included with most Linux distributions. The RedHat 8.0 installer even allows you to create LVM volumes during initial install. LVM offers capabilities previously only found in expensive products like Veritas. If you plan on using LVM, I really recommend doing so on a RAID system, either hardware or software -

Using sudo   2015/02/02 TonyLawrence
- I'm sure that there are more poorly written man pages, but "man sudoers" (which is how you find out about "sudo") is among my all time favorites for poor explanation. Let's clear that up. -

GPG/PGP Basics   2014/10/29 anonymous
- Using gpg for encryption, understanding the basic use of GPG for new users. Recently someone asked me for a GPG or PGP public key so that they could send some sensitive material to me by email. -

Automating Program Startup  
- automating program startup methods. When you need something to start automatically, there are several ways to do it. Which one you use depends on your specific needs. -

How can I recursively grep through sub-directories?   2013/07/18 IrfanRashid
- How to grep through sub-directories whether or not your Unix has recursive (GNU) grep. -

How can I automate an ftp transfer?   2011/02/03 Bagbot
- If your script is complex, I'd use use Perl Net::FTP or Kermit. You can also use "here" files fpr simple cases: -

(SCO Unix)How can I send email attachments from the command line?   2011/02/01 anonymous
- Sending attachments from the command line with mutt, uuencode and other methods. If it's just arbitrary text or a file you want to send, and don't care about it looking like a real attachment, you can use ordinary "mail" ("mailx" on some Unixes) at the command line. However, that's NOT a mime attachment - it's just your file mixed in to the mail message. However, some mail clients will see it and treat it as a real attachment, so this may be "good enough": -

(SCO Unix)How can I rename multiple files using wildcards?   2010/02/10 TonyLawrence
- (SCO Unix) How can I rename multiple files using wildcards if I don't have Linux "rename"? -

(SCO Unix)How do I clear log files?  
- (SCO Unix) There is a proper way to clean out log files - don't make the mistake of removing them! -

(SCO Unix)How do I add a default route?  
- How to add a default route on various versions of SCO Unix and have it survive a reboot. -