Unix Stuff 1 Base64 Encoding a String {code:none} echo some-string | openssl enc -base64 -e {code} Use the -d option to decode. 1 FTP Login If your shell login works but your FTP or secure FTP login doesn't, check your shell login script and make sure it doesn't generate any console output. 1 Emacs Essentials General: Command keys like C-x means Ctrl-x. Mode (meta) keys like M-x means Meta-x (use ESC, Alt or Windows key as meta key) {code:none} F10 - Navigate the menus in a text console (ncurses) emacs. C-x C-c - Exit; allows you to save modified buffers. {code} 1 vi Essentials Use ESC to put vi in command mode, 'i' or 'a' to type text. {code:none} :q - Exit, no save (add ! to discard changes) :x - Save and exit i - insert text a - append text yy - copy current line Nyy - copy N lines (including current one) dd - delete current line Ndd - delete N lines (including current one) p - paste /string - search for 'string' from cursor / - repeat search {code} 1 Searching The File System {code:none} find . -name "filename.*" (searches for files) find . -exec grep -H 'pattern' '{}' &#92;; (searches for 'pattern') {code} 1 Text Find/Replace in Multiple Files {code:none} find . -name Root -exec sed -i s/olduser/newuser/g '{}' &#92;; {code} Replaces 'olduser' with 'newuser' in all files named Root under the current directory tree. 1 Viewing a growing log file {code:none} tail -f filename {code} 1 Running an X11 virtual frame buffer Java applications running on servers sometimes require a running X11 environment and a display server they can contact in order to run or function properly. (As an alternative, setting the Java system property java.awt.headless=true usually eliminates this requirement. However, it didn't in my case.) You can start a virtual X11 server with the following command: {code} Xvfb :any-free-display-number {code} Then do a {code} setenv DISPLAY :your-xvfb-display-number.0 {code} And run your application. In a Java application I was running using this approach, the fonts in image files generated by the application were scaled wrongly. The reason for this was a wrong DPI setting of my virtual frame buffer (Xvfb uses the default DPI setting initialized with Xserver on the system). This was 100 DPI in my case and I wasn't in a position to change that. However, I was able to trick Xvfb into returning a DPI value other than 100 when queried by an application. This was possible because the dimension in pixels of the virtual frame buffer was irrelevant to my application (i.e. I could run Xvfb with any screen resolution). The follwing table shows a few possible screen resolutions and resulting DPI values. {table} #Pixels|Screen Size (mm)|Screen Size (mm) Rounded|Resulting DPI 1|0.254|0|#DIV/0! 2|0.508|1|51 3|0.762|1|76 4|1.016|1|102 5|1.27|1|127 6|1.524|2|76 7|1.778|2|89 8|2.032|2|102 9|2.286|2|114 10|2.54|3|85 11|2.794|3|93 12|3.048|3|102 13|3.302|3|110 14|3.556|4|89 15|3.81|4|95 16|4.064|4|102 17|4.318|4|108 18|4.572|5|91 19|4.826|5|97 20|5.08|5|102 21|5.334|5|107 22|5.588|6|93 23|5.842|6|97 24|6.096|6|102 25|6.35|6|106 26|6.604|7|94 27|6.858|7|98 28|7.112|7|102 29|7.366|7|105 30|7.62|8|95 31|7.874|8|98 32|8.128|8|102 33|8.382|8|105 34|8.636|9|96 35|8.89|9|99 36|9.144|9|102 37|9.398|9|104 {table} As an example, this is what I had to do to have my Java application generate images for a target system with 76 DPIs (see line 3 in the table above, 3x3 in the command means the screen resolution): {code:none} Xvfb :99 -screen 0 3x3x24 & setenv DISPLAY :99.0 <run my Java application> {code} By the way, you can query the properties of your display with the xdpyinfo command. For example: {code:none} xdpyinfo -display :99 {code} 2007-09-03 15:40:51.238 2007-04-26 15:00:31.55