System Notes Org

Would you like an easy way to send files to someone outside of your local network, or quickly test a mail server? Well the old "mail" command is still available, and it comes in handy for sending config files, or using within a shell script. This is all you need: $ mail -s test me@company.com That's the shortcut. If you want more details, you can read the rest of the post... Using the mail command 1) Use Mail Interactively to read mail a) type Mail b) enter the number of the message to read, press enter c) press space to page down, n for next message d) ? for help e) q to quit 2) Use mail Interactively to send mail a) type mail command followed by email address b) Enter subject, press enter c) Enter text of message d) press Ctrl-d on a line by itself when finished e) Enter CC: if desired, or press Ctrl-d again $ mail user@company.com Subject: test Here is my test message <Ctrl-d> Cc: <Ctrl-d>$ For a little less work, add the subject to the command prompt. ...

Did you ever wonder if there was an easy way to send an example file for someone to look at, but still keep your private information safe? Sure you can use a sed, or perl one-liner, as I discussed: using-bash-and-sed-to-modify-text-file.html , but why not use search and replace in vi / vim before publishing your info? That way you can see exactly what you are changing. Remember, while vim is installed by default on most Linux distros, is also available for Windows, and it is free -- http://www.vim.org Suppose you have part of a log file, or nmap output that contains real hostnames, a real domain name, and real IP addresses. You want someone to help you troubleshoot something, but you don't what to give the real info for everyone to see. Start with the info in a text file, such as this: Host realhost-1.realdomain.com (192.168.0.54) appears to be up. Host realhost-2.realdomain.com (192.168.0.55) appears to be up. Host realhost-3.realdomain.com (192.168.0.56) appears to be up. Host...

I explained how to get a list of hosts using nmap -- using-nmap-to-generate-host-lists.html , but here is another look at the subject. The question is, how do I ping multiple hosts to find out which ones are down? Sure this could be considered a topic of system monitoring, but maybe you just want to reboot a bunch of machines, and make sure they all come back online. This quick check will tell you whether there is a problem or not. Here are three methods for pinging a list of hosts: 1.) for host in `cat all.txt `;do ping -c 1 $host; done 2.) nmap -sP -R -iL all.txt 3.) sudo fping -u < xyz/all.txt First, we assume that you have a text file named all.txt that contains a list of hostnames, one per line. Obviously, the examples here contain fake hostnames, domain names and IPs, as described in another article about vi: vim-tips-search-and-replace.html . --- all.txt --- xyz-1 xyz-2 xyz-3 xyz-4 xyz-5 xyz-6 xyz-7 xyz-8 --- end all.txt --- 1.) Use a for loop in ...

Did you ever cat a file that caused the terminal to display all kinds of strange characters? Pressing Ctrl-C and Enter, or typing clear doesn't get the console back to normal. The characters are there, but they are unreadable. A quick way to fix this is to use "reset" -- type: $ reset That should bring the console back to normal. Of course, if you just want to clear the screen, you can type "clear" ("cls" in DOS, or a Windows command prompt).

While researching anti-spam techniques, I came across an anti-telemarketing technique that has proved quite useful. Within a few weeks, it noticeably reduced the amount of telemarketer calls I was getting. Here is the original article, which I copied: The original site seems to be down ( http://home.comcast.net/~dakine_101798/spambeater.htm ): so I have a copy on my systemnotes.org site -- http://www.systemnotes.org/notes/security/Defeat_Telemarketers_for_FREE.html Defeat Telemarketers for FREE! Yes! You can stop Telemarketers COLD! Now you can save that $40.00 you were thinking of spending on a TeleZapper . You can even save a couple bucks on the eBay Auctions for this sound file. The TeleZapper is a device that plays the first tone in the three tones that precede the telephone company's historic " This number has been disconnected " message. Most telemarketing predictive dialers listen for that tone, and when it is present t...

The article linked below is a nice introduction to the Vi editor. People often ask why they have to learn vi, or vim. One important reason is that it is the editor most likely available on any linux or unix system you may have to manage as a sysadmin. Less experienced sysadmins may say that they can just install joe, or pico, or something similar -- until I show them 1200 linux boxes that we have to manage! Anyway, once you have the basics, you can add more knowledge as you go. First realize that there are two modes - command mode, and editing mode. "i" puts vi into editing mode, and [esc] goes back to command mode. You can get by with just a few commands at first: vi file.txt i (insert -- go into editing mode) [esc] (move around) [esc]:wq (save) [esc]:q! (quit without saving) read more | digg story Links: http://www-acs.ucsd.edu/info/vi_tutorial.php http://www.viemu.com/vi-vim-cheat-sheet.gif

Did you ever look for a binary, and as a last resort download the source to compile yourself?   Of course you were disappointed that the program would not be part of your package management system. Usually you have to run something like this:   ./configure   make   make install An easy way to create an .rpm or .deb file from source is to run checkinstall instead of "make install" during the standard install from source. http://freshmeat.net/projects/checkinstall -- CheckInstall Freshmeat Page http://checkinstall.izto.org -- CheckInstall Home Page CheckInstall keeps track of all files installed by a "make install" or equivalent, creates a Slackware, RPM, or Debian package with those files, and adds it to the installed packages database, allowing for easy package removal or distribution.

Sure, you can now download music from the iTunes store without DRM but that doesn't mean you should just willy nilly start sharing that music with your friends. For one thing, it's illegal. For another, your account information is embedded into that m4a music file. Don't believe me? Try this yourself. The site is mostly for Mac users, but the strings command works in linux, and cygwin for Windows. This link has interesting comments as well. read more | digg story

VNC is an excellent way to remote control linux and Windows machines. Here is a description, and links to the programs. Blogger Digest: Using VNC And Redhat Linux x11vnc official site Real VNC Server official site TightVNC TightVNC software UltraVNC UltraVNC software

You May know those BIG things But Did you know these? Excellent list of easy firefox tips to implement -- e.g., press Esc to stop animated gifs from moving... # To quickly find any word in a web page type /word it will highlight the word and press Ctrl+G to “Find Again” that same word again # If you wish to remove an item from your Address Bar Drop down menu,Highlight it without clicking and use Shift+Delete. # To stop animated gifs from moving, press the ESC key. read more | digg story

The P2P network's founder Mark Gorton is in the fight of his life. read more | digg story

These RCHE study notes were designed to be brief reminders of what you should already be familiar with. This topic covers HTTP server configuration. One thing to be aware of when working with Apache and the 2.6 kernel is SELinux. Overview of SELinux SELinux, is a Mandatory Access Control (MAC) security system for Linux based on the domain-type model. It was written by the NSA ( http://www.nsa.gov/selinux/ ) and is comprised of a kernel module (included in all 2.6 kernels), patches to certain security related applications, and a security policy. More info: http://www.redhat.com/magazine/001nov04/features/selinux/ Study Notes Here are the brief steps from my RHCE study guide to help you remember the steps to configure a virtual host, and configure permissions. * HTTP/HTTPS install httpd, check context with ls -Z   Q: Create a virtual host www1.example.com w/ subdirectory /var/www/html/www1   A:    1) install httpd, modify /etc/httpd/conf/httpd.conf file  ...

About P2P P2P software is free, and legal to install and use, but it does make sharing of copyrighted material easy to do, and that is not legal. Are people still using P2P software after Napster got shut down? Yes, they certainly are. Free music downloads? Free software? -- well be careful about copyrighted materials, but the technology is interesting nonetheless. One of the best ways to get a large file, such as a linux iso file, is to use bit torrent. Dangers What are the dangers, and inconveniences of using peer to peer file sharing software such as Limewire, eDonkey, Azureus, or Bittorrent? 1.) The content quality is only as good as how trustworthy the peers are 2.) Some content is copyrighted, and may be illegal to share or download on this type of network 3.) Content may contain viruses, trojans, and decoys 4.) Excessive traffic may cause your ISP to limit your bandwidth usage 5.) Some downloads may take days to complete 6.) There may be pornography disguised as something ...

After one year and five days of waiting: a brand new Vim release! This is a stable version. There are many bug fixes and updated runtime files. No amazing new features. Upgrading from a previous version is highly recommended... Note that Vim works on Linux, Windows, Macintosh, and other systems. This is an excellent free editor with syntax highlighting that is great for programming, text manipulation, and HTML editing. If you plan to be a sysadmin, you have to learn vi. I use it for scripting, text editing, and blog posting, among other things. read more | digg story

In Linux, directories are not accessible until the device is mounted. This is usually done at startup by the mount command which uses the /etc/fstab file. Files that start with a dot "." are hidden, but not completely (you can do ls -a to see the files). An example is the ~/.bashrc file. You can also hide files in a directory name that starts with a dot, e.g. ~/.ssh Now for the real trick Entire directories can be hidden, simply by mounting another device on top of the directory. The original files will still be in tact, but not visible until the device is remounted. First, find a device that is available to mount (boot is nice, because it is usually small). $ mount /dev/hda1 on /boot type ext3 (rw) ... etc... Then make your stealth directory, copy files to it, and mount a directory over it. $ cd /mnt $ mkdir stealth $ touch /mnt/stealth/somefile.txt $ ls /mnt/stealth/ somefile.txt $ mount -t ext3 /dev/hda1 /mnt/stealth ls /mnt/stealth/ config-2....

Google has some excellent webmaster resources, and some fun and useful gadgets that can be quickly added to a website or blog. Just as with any good design, remember not to over do it. http://www.google.com/webmasters/gadgets/ Here is what Google says about their gadgets: ------------------------------------------------------------------------------ Enhance Your Own Website Add Google Gadgets to your webpage You can now use Google Gadgets to make your webpages even more interesting and useful to your visitors. For instance, you can add your city's current temperature or a quote of the day to your own page. Just pick the gadget you want from our directory of "Google Gadgets for your webpage," customize that gadget, and copy-and-paste the HTML into your page's source code. Then, reload to see the gadget on your page. Find gadgets for your webpage. ------------------------------------------------------------------------------ If you want to find something about cooking...

There are two basic categories for web site tracking. 1. Online (Embeded Tracking Code) 2. Log Analysis (Software) Onine This type of analysis has the advantage that nothing needs to be installed on the web server. The disadvantage is that every page requires modification. That is not much of a problem for blogs, or generated content, but it can be tedious to modify a large number of pages by hand. Google analytics is free, very simple to use, and produces excellent reports. Here are the instructions from their site: https://www.google.com/support/analytics/bin/answer.py?answer=27323&hl=en_US How do I track a new website? There are two simple steps required to start tracking a new website: the creation of a new website profile, and the addition of Analytics tracking code to all of the pages you wish to track. Create a new profile 1. From the Analytics Settings page, click Add Website Profile 2. Select Add a Profile for a new domain 3. Enter the URL of the site you will be tra...

Sure we all want a nice looking website, but that doesn't mean you have to use lots of graphics and flash animation. It turns out, you'd be much better off using text instead of graphics. Here's the proof... Use text instead of graphics on your website Nowadays, it seems that every site owners knows how his site should look like: visually appealing, with a large amount of graphics (or even Flash) and, of course, with plenty of images of people, preferably women, preferably barely clothed (or naked). But reality is that what works isn't what people, who barely know anything about web design, think to work. read more | digg story

This is a very simple topic, but sometimes little tips can save you a lot of time. Windows & Linux First select the text, or item, or location to paste to: Copy = Ctrl-c, or From the "Edit" menu, select "Copy" Cut = Ctrl-x, or From the "Edit" menu, select "Cut" Paste = Ctrl-v, or From the "Edit" menu, select "Paste" You can copy and paste text, graphics, files, etc. In Windows, you can copy and paste files within Windows Explorer, or you can drag and drop them. Linux All of the above, plus: Copy = Select text with the mouse Paste = Click the middle mouse button vi If you want to copy and paste in vi, that's another topic. To copy a line in vi, type yy (yank line), and then p (paste after), or P (paste before). To copy a word, use yw (yank word). To copy five lines -- 5 yy, or five words -- 5 yw, or to paste something five times 5p. Here are some good tips on vi http://www.vim.org/tips/tip.php?tip_id=312 . By t...

1. Update every single piece of software on my system with a single action. This is one of the main reasons I run Linux. Sure, Windows has Windows Update, but that only updates the operating system, Office, and a few other things. For every Linux distribution I've used (Gentoo, Red Hat, Suse, Ubuntu), updating is simple. read more | digg story

"Web 2.0" in just under 5 minutes. This is a slightly revised and cleaned up version of the video that was featured on YouTube in February 2007. Link: http://youtube.com/watch?v=NLlGopyXT_g

Out of the plethora of chores that we do each day, which ones make up the top seven activities of forgetful system administrators? To begin, you might ask yourselves if the answer is quantitative or qualitative. Let's think about it for a minute. Forgetting to Delete a Former User's Account Forgetting to Regularly Search for Rootkits Forgetting to Use a Trouble Ticket Tracking System Forgetting to Set Up Technical Documentation and Creating a Knowledge Base Forgetting the Risks of Flash Memory Drives Forgetting to Manage Partial Root Access Forgetting Courtesy read more | digg story

Eric Meyer, CSS Guru gives us a run down on some extreme CSS Reset. Think of these as a starting point for creating your own defaults, in addition to being a way to illuminate the nature of browser defaults. Simply the act of taking those defaults into consideration and thinking about them closely puts you ahead of 99% of your peers. read more | digg story

Someone put together a list of just about every color related resource (worth mentioning) in the known universe. Designers rejoice! http://www.colorschemes.org read more | digg story

Scroll down for the top 10 list. From http://www.lifereboot.com read more | digg story

The command history is stored in ~/.bash_history. The history typically contains the last 500 commands typed at the shell prompt. You can view the history by using the history command. history | less Then you can search for a command. e.g. what was the name of that directory I created yesterday? Oh, yeah, I can search history for the mkdir command by using the slash. /mkdir You could also use grep, but with less, you can see the surrounding commands, as you often want to see the sequence of what was done. History Shortcuts !! - Executes the last command !902 - Executes command number 902 (from the history list) !service - Executes the command whose string matches the most recent history entry Up / Down - The most common shortcut is to simply use the up and down arrows to scroll through the bash history. Example If you recently restarted the network service, and then wanted to restart it again, you might do something like this; service network restart ping somehost.example.c...

IP Forwarding Effectively makes a Linux box act as a router Is usually used with two network interfaces (one internal, and one external) Can be used with firewall services and is often used for NAT Steps to Turn on IP Forwarding  1) Modify /etc/sysctl.conf      vi /etc/sysctl.conf      add this line:      inet.ipv4.ip_forward=1  2) Make the Change Active      sysctl -p  3) To View Current Settings:      sysctl -a | grep ipv4 More info can be found on the redhat site: https://www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/security-guide/s1-firewall-ipt-fwd.html We'll leave firewall rules for another topic... rhce linux

This procedure assumes you have console access, and are authorized to make changes to accounts on the machine, including root. If you own the machine, you can boot into single user mode, and change the password, or create an account. If using grub (you should see a blue bootup screen), press "a", "space", "1", "enter" a 1 That will boot to single user mode. Then you can change the root password passwd Then reboot Ctrl-Alt-Del You should create user accounts other than root. Use the useradd command. useradd someone passwd someone rhce linux

Study notes for any exam are difficult enough to find, but RHCE material seems even more scarce. This article tells how to prepare for one of the objectives, which is configuration of an SMTP server. RHCE Study Notes I wrote up some study notes as I was preparing for the RCHE exam. Here are some quick notes based on the official RedHat objectives , labs, and possible questions I thought might be reasonable requests. SMTP Related Questions install sendmail, sendmail-cf, sendmail-doc (optional) Q: Configure mail server to accept internet email A: modify /etc/mail/sendmail.mc 1) cd /etc/mail 2) vi /etc/mail/sendmail.mc search for 127.0, put dnl at the front of the line 3) make or m4 sendmail.mc > sendmail.cf service sendmail restart Q: Mail alias A: modify /etc/aliases, run newaliases Q: Receive mail for DomainX.example.com A: modify sendmail mc as above, and add domain to /etc/mail/local-host-names ...

For Linux / Unix Follow as instructed For Windows Download cygwin from http://cygwin.com For instructions, see this article: http://systemnotesorg.blogspot.com/2007/04/use-cygwin-to-run-linux-on-windows.html Two Easy Steps for One-Liners e.g., you have a list of servers, and would like to do something, such as ping each one, or check their IP address. Here is a quick two-step process, with a one-line shell script that can be run from the command line. 1) Create a Text file, with one hostname per line 2) Run a for loop on the file $ cat servers.txt server01 server02 server03 $ for host in `cat servers.txt`;do host $host;done server01.example.com has address 10.10.10.10 server02.example.com has address 10.10.10.11 server03.example.com has address 10.10.10.12 $ If you want different output, you can use awk, but that's another topic. Notice a few things about this one line script. 1) Each command is separated by a semicolon ";" 2) The ba...

Yes, not only can you run Linux from a CD -- http://systemnotesorg.blogspot.com/2007/04/how-to-get-started-with-linux.html , but you can also install it in Windows, and run it as a Windows program. You get a standard linux bash shell, and even X, with a little configuration. What Is Cygwin? (from http://cygwin.com ) Cygwin is a Linux-like environment for Windows. It consists of two parts: A DLL (cygwin1.dll) which acts as a Linux API emulation layer providing substantial Linux API functionality. A collection of tools which provide Linux look and feel. The Cygwin DLL currently works with all recent, commercially released x86 32 bit and 64 bit versions of Windows, with the exception of Windows CE. Note that the official support for Windows 95, Windows 98, and Windows Me will be discontinued with the next major version (1.7.0) of Cygwin. What Isn't Cygwin? Cygwin is not a way to run native linux apps on Windows. You have to rebuild your application from source if you want it to r...

CNE Not as popular as it once was. MCSE One of the most popular has been the MCSE. CCNA It is always good to have some network knowledge. RHCE One of the most challenging exams in the industry. All hands-on lab exam. A+ Not very difficult, but shows some knowledge of hardware, and is a prerequsite for HP exams HP APS HP Acredited Platform Specialist. Requires CNE, or MCSE and A+ as prerequsites, but is a fairly easy exam that deals mainly with hardware. Other Specialties Oracle, Citrix, etc. There is plenty of demand for MCSE's, but experience counts as well. RHCE is another important one, as is the CCNA. Other certs are useful, but more so in smaller companies, or as a consultant. You will need more experience to get into a big company, but jobs tend to be more specialized. You would either be a server admin, network admin, or dba, whereas in a smaller company you might be all three. Another important thing to help get interviews is a college degree. You can use some of your...

Have you always wanted to find out more about linux, but were not sure where to start? Here is a little information on where to find, and how to run and / or install a linux distribution. What is Linux? Linux is the kernel, or core part of an operating system that is free from any software licenses. Free to download, and install on as many machines as you like. Here's an explanation from http://www.gnu.org/ The GNU Operating System - Free as in Freedom What is the GNU project? The GNU Project was launched in 1984 to develop a complete Unix-like operating system which is free software: the GNU system. Variants of the GNU operating system, which use the kernel called Linux, are now widely used; though these systems are often referred to as "Linux", they are more accurately called GNU/Linux systems. GNU is a recursive acronym for "GNU's Not Unix"; it is pronounced guh-noo, approximately like canoe. Trying Linux First, you may not have known that ...

...and maybe make some money. An article I posted on http://systemnotesorg.blogspot.com discusses how to get more traffic to your site. http://systemnotesorg.blogspot.com/2007/04/search-engine-optimization.html Now let's concentrate on how to set up a blog. With blogger, you don't have to know any html, but if you do, it helps. Getting Started First go to http://www.blogger.com and create a blog. If you already have a gmail account, you have completed the first step. It is really simple, and they walk you through it. Think of a name, and what you would like to write about. O.K., so you have a blog, now what? There is a book title that should help you keep on topic -- " No One Cares What You Had for Lunch " Then start posting. You can set up your blog to receive email, so posting is very easy. Just send an email to the address you set up under settings / email. Making money Well, keep posting something useful, but If you want to make money, don't wa...

Sure this blog is more about systems and programming than it is about marketing, but if you're building a website or blog, you probably have at least some interest in SEO ( Search Engine Optimization ). Basically, that means having other quality sites link back to your site, which is what makes it appear higher in search engines such as google Here are some things to check out: 66 Ways to Build Links in 2007 . If you are interested in making money from your blog, or learning how to get more traffic, check out http://problogger.net . Try a google search on seo, if you want to learn more. And don't forget about the excellent webmaster tools at google. http://www.google.com/support/webmasters and specifically, How can I improve my site's ranking? -- http://www.google.com/support/webmasters/bin/answer.py?answer=34432&hl=en

This shell script demonstrates how to write to a text file, and then modify the contents. #!/bin/sh # modfile.sh # by ScottM, 04/12/2007 # demonstrates writing text to a file, and then using sed to modify it. TESTFILE=test.txt FRUIT=banana # add some content to the file (note: file will be overwritten) echo "apple" > $TESTFILE # modify the content sed -e "s/apple/& $FRUIT/g" -i $TESTFILE # sed uses the "s" option, which uses regular expressions to search and replace text # "s/apple/" means search for any lines that contain the characters "apple" # "& " means use the results of whatever was found # "/& $FRUIT/g" -- replace "apple" with "apple banana", # the g is for global, or all lines containing the pattern # output: # $ cat test.txt # apple banana # $ Sed One Liner This is really only a one line script, commonly referred to as a on-liner, so we don't really need a...

Multi Gnome Terminal Install Note: This procedure is for non-standard, unsupported software. The dag repository is outside of Redhat's control, but has some very useful software. Since multi-gnome-terminal has several dependencies, it is easier to install using yum. First, Install Yum * Install yum from your distribution $ rpm -Uvh /RPMS/rhel-3-i386-as/yum-2 .2.0-1.noarch.rpm * Modify /etc/yum.conf Standard yum.conf for rhel-3-U6 (change as required): [main] cachedir=/var/cache/yum debuglevel=2 logfile=/var/log/yum.log pkgpolicy=newest distroverpkg=redhat-release tolerant=1 exactarch=1 obsoletes=0 [rhel-3-U6-i386-as] name=Red Hat Enterprise Linux 3 Update 6 i386 AS baseurl= http://yum.mydomain.com/rhel-3-U6-i386-as/ * Then, add the dag repository to /etc/yum.conf [dag] name=Dag RPM Repository for Red Hat Enterprise Linux baseurl= http://apt.sw.be/redhat/el3/en/i386/dag Now, Install and Configure multi-gnome-terminal 1. Install multi-gnome-terminal 1. yum inst...

An easy way to get a list of hosts from a single domain that you are a part of, is to query DNS host -l mydomain.com But that is not always practical. Sometimes you have machines that are in different domains, but they all are part of a network you manage. Rather than trying write a script that pings hosts and reports the output, just use nmap for a very fast scan. To scan all hosts in a list of subnets 1) Create a subnets.dat file with one subnet on each line: $ cat subnets.dat 192.168.0.* 192.168.1.* 2) Run nmap with the subnets.dat file as input $ nmap -sP -R -iL subnets.dat Reading target specifications from FILE: subnets.dat Starting nmap V. 3.00 ( www.insecure.org/nmap/ ) Host (192.168.0.0) appears to be down. Host box1.mydomain.com (192.168.0.1) appears to be up. Host box2.mydomain.com (192.168.0.2) appears to be down. Host box3.mydomain.com (192.168.0.3) appears to be up. Host (192.168.0.4) appears to be up. ... Notice how names are resolved ...