Back to Newsletters KEYWORDS= Davrom Consulting Newsletter - Issue # 45 - Dated: 22 Dec 2009 From the desk of David Clark Well another Christmas is upon us and 2010 is just around the corner. I would like to take this opportunity to wish all of our customers and readers a very Merry Christmas and a blessed and prosperous New Year. For us as usual, we will only be closed for the actual public holidays. And in keeping with tradition, I have included the beloved ASCII Christmas tree in this newsletter.
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Looking forward to keeping in touch with you all in the new year. I would like to thank the reader for their time in reading this newsletter. David.M.Clark UNIX Quote You really know you need a holiday when you start to dream you are still at work at the command line... David Clark OpenFire and Pidgin If you have a need for your staff to use instant messaging rather than just relying on internal e-mail, consider the use of OpenFire on your Linux server. Unlike external messaging systems like ICQ, MSN, Google and Skype, OpenFire runs on your own internal Linux server and therefore any company sensitive information is only ever seen, passed or stored, internally. As I used to say to my UNIX students, if you don't want a third party to read an e-mail (and also applies to messaging) out there on the Internet, don't send it. OpenFire uses its own internal database so you don't need to use MySQL to handle the message storing which was something I took into consideration as a requirement. OpenFire has a well designed web interface for setup and management of your messaging accounts and groups - and again runs on your local Linux server. I have tried a few instant messaging clients with OpenFire and I have found that the Pidgin instant messaging that comes with Linux is one of the best. Pidgin is also available on MS Windows and MAC and we have been running Pidgin via OpenFire here in our office between Linux and Windows desktops successfully for some weeks now. A good alternative to Pidgin is the Spark message client that is also released by the makers of OpenFire. Another message client that we have tested here is called Pandion and was suggested by a colleague to try. We use the Pidgin message client here at Davrom because of the mix of Linux and Windows message client familiarity regardless of the desktop. Pidgin will also give your staff the ability to message on-line with the Internet with the mainstream providers (Google, ICQ, MSN, Skype) as well as using OpenFire for internal messaging at the same time. A nice product that is simple to install and keeps all of your messages completely private - even if it is an election as to who is going to the shop today for lunch. Tape drive files in /dev (At the time I decided to write an article on this subject the very issue happened to a site that I support.) The /dev directory in UNIX and Linux is the place where you will find the device node files. Files that let UNIX/Linux talk to the hardware using human friendly names (sometimes not so friendly, but still logical). These files are referred to as "character special", starting in a directory listing with the letter "c", or "block special", starting with the letter "b". In the case of Linux the name is usually /dev/st0 and in SCO it is /dev/rStp0 (or /dev/rct0). These special tape devices should always be shown as "device node character special" files (starting with the letter "c" in a directory listing) when you view them and should never be "regular" files. If you perform the commands: ls -l /dev/st0 for Linux, or: l /dev/rStp0 for SCO, you should see the file name listing starting with the letter "c" for the first character in the permission bits. The very first character you should see is something like: crw-rw-rw- 5 root root 46, 0 Dec 22 23:09 /dev/rStp0 (example of a SCO tape drive /dev node file) The following examples shows a tape device file name has been used either when a tape drive is not present or has been misspelled: -rw-rw-rw- 5 root root 50000000 Dec 22 23:09 /dev/rStp0 or -rw-rw-rw- 5 root root 50000000 Dec 22 23:09 /dev/rSpt0 In either case, the tape drive file is not a tape device but is in fact a tape archive file created by the backup software using tar, cpio, dd or other third party tape archive utility. While being a valid file in itself, it is useless and in the case shown here occupies 50MB of root filesystem disk space. In the worse case scenario I have seen automated backups running to non-tape /dev node files that have eventually filled the entire root filesystem. This is because UNIX/Linux honours our use of creating archives to files regardless of whether they are device (character/block special files or regular files). To check if you have regular files in your /dev directory you can use the command: ls -l /dev | grep "^-" and this will show you any regular file in the /dev directory (starting with a "-". It is highly unusual for regular files to be placed in the /dev directory and is poor practice for using /dev if regular files are knowingly placed in /dev. In most cases the presence of regular files in /dev are simply typos or that can be removed. Naturally if you are unsure of whether such files can be removed, it is always wise to check with your application or support contacts before removing the files unless you can clearly see they are mistakes. From the Trenches Some comic or not so comic relief from the support days gone by. IT staff set strategic directions in office coffee drinking. Being a bit fussy when it comes to coffee and the brands of instant coffee available in the workplace, I was often teased by my workmates for bringing my own favourite little jar of instant coffee (Nescafe Gold Blend) to work. In one company I worked for I was in the office kitchen making my coffee when I was suddenly called away and I ended up leaving my beloved jar of coffee sitting on the kitchen bench. When I returned later to get my jar I was struck with horror that my formerly full jar was now down to the last granules at the bottom. The vultures had swooped down on my defenceless jar and left me nothing but the bones (dusty bits). I brought a new jar of coffee that night and thought nothing of my massive coffee losses over the next few days. I vowed I would never let this happen again. Some days later I was in the kitchen again, with my beloved little jar, but noticed that the new office coffee was the same brand, except in massive tins. I was in paradise! As it turned out a few of the directors of the company had helped themselves to my jar of coffee on that fateful day and struck by the better quality and taste had decreed that this would be the new brand of coffee in the office. Needless to say I never needed to bring my own coffee while I worked there for some years. I was always quietly proud that I had engineered such a feat to change the coffee drinking of the whole company without a UNIX command line in sight. Tech Tip A sometimes useful tool that ships default on SCO systems and is available for Linux is the "banner" command. The banner command allows you to display the words of up to ten characters in length on the screen in large block letters. Some examples of the use of the banner command: banner testing laser printer | lp -dlaser This will print out the three words in block letters to the printer laser a your system. banner did you get this email | mail -s"First E-mail Test" user@my.com.au This will e-mail the block letter words to the e-mail recipient user@my.com.au. banner backup >/tmp/backup_log This will place the word "backup" in block letters into a file called /tmp/backup_log. Subsequent logging of the system backup could then be appended to the /tmp/backup_log file with the ">>" characters and then printed or e-mailed to show the system backup outcome. Handy utility and fun to play with as well. Back to Newsletters 
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