{"id":468,"date":"2006-03-07T18:28:00","date_gmt":"2006-03-07T18:28:00","guid":{"rendered":"http:\/\/markwilson.me.uk\/blog\/2006\/03\/quick-introduction-to-linux-for.htm"},"modified":"2007-05-26T19:31:04","modified_gmt":"2007-05-26T18:31:04","slug":"quick-introduction-to-linux-for","status":"publish","type":"post","link":"https:\/\/www.markwilson.co.uk\/blog\/2006\/03\/quick-introduction-to-linux-for.htm","title":{"rendered":"A quick introduction to Linux for Windows administrators"},"content":{"rendered":"

\"LinuxI’ve written previously about my various attempts to cross-train in Windows<\/a> and Unix<\/a>. Recently, I began running Sun Solaris<\/a> 10 x86 on one of my machines, more recently I’ve installed SUSE Linux<\/a> 10.0 and this week, I’m attending a training course to learn about Red Hat Enterprise Linux<\/a>.<\/p>\n

What follows might be useful for anyone thinking of making the switch (or just picking up some new skills). I should stress that I’m a Unix\/Linux<\/a> newbie (unless you count some Unix systems programming back at uni’ in the early 90s) so these notes are probably incomplete and I might come back and edit them later. I don’t intend this to be a guide for integrating Linux and Windows either – more of a quick conversion for Windows administrators starting to work with Linux. Also, whilst these notes are based on Red Hat Enterprise Linux 4, they should hold true for most recent Linux distributions (I’ve tested them on SUSE Linux 10.0) and they shouldn’t be too alien for other Unix variants (although the commands may be a little different).<\/p>\n

Whatever the Linux distribution, the kernel is controlled by kernel.org<\/a>. This is the part of the operating system based on the original work by Linus Torvalds<\/a>. The differences between Linux variants come at the next level with the various utilities added as part of individual distributions, including the graphical environments (e.g. GNOME<\/a> and KDE<\/a>).<\/p>\n

Some vendors (e.g. Red Hat and Novell) have split their products into a free-to-download version with frequent upgrades and rapid adoption of new technology (e.g. Fedora<\/a>, SUSE) and a more stable version with predictable release cycles and a subscription-based licensing model including support (e.g. Red Hat Enterprise Linux, SUSE Enterprise Linux), aimed at corporates who need to maintain standards. Some distributions also include utilities for keeping the system up-to-date (although these may also require an appropriate entitlement).<\/p>\n

Installation of a Linux system is generally straightforward. The major distributions make life easy with bootable CDs and DVDs and comprehensive setup\/installation routines (e.g. YaST). Having said that, if problems are encountered, they are not always easy to resolve (it took me considerable time to resolve a recent issue with installing SUSE 10.0 on an IBM ThinkPad<\/a>).<\/p>\n

Once installed, Linux can be used in either command line interface (CLI) or graphical user interface (GUI) mode. Unlike modern Windows operating systems, the Linux GUI is separate from the operating system itself and it is possible to run several CLI and GUI sessions (called virtual consoles) simultaneously. By default Ctrl-Alt-F1 to Ctrl-Alt-F6 are CLI user virtual consoles, whilst Ctrl-Alt-F7 will run a GUI interface. Multiple GUI sessions can be started using the startx<\/code> command.<\/p>\n

The Linux root user is analogous to the Windows administrator but (largely because Linux expects users logged in as root to know what they are doing) Linux doesn’t tend to issue “are you sure?” prompts and so it is far easier to perform something destructive by mistake when logged in as root. Although it’s also good practice to run as an unprivileged user in Windows, this should definitely be the norm in Windows. Many GUI applications (and some CLI ones) allow for escalation of privileges (in a similar manner to the user access protection feature in Windows Vista<\/a>).<\/p>\n

As for Windows (with command<\/code>, cmd<\/code>, wsh<\/a> and soon msh<\/code><\/a>), Linux has a variety of shells\/command interpreters available for use. Linux distributions use the Bourne-again shell<\/a> (bash<\/code>) by default but may also ship with other shells including the original Bourne shell<\/a> (sh<\/code>), C shell<\/a> (csh<\/code>) and Korn shell<\/a> (ksh<\/code>).<\/p>\n

Linux uses the X Window<\/a> system for GUI operation; however X Window doesn’t dictate the look and feel – it is simply an application that provides the ability to draw on the screen. X Window is a client\/server application, with the X server handling the monitor, keyboard and mouse and various X clients interacting with the X server. Examples of these X clients include the display manager (handling logins), the window manager<\/a> that controls the look and feel (e.g. Metacity, KWin), the desktop environment (e.g. GNOME, KDE) and a variety of other x client applications (file browsers, web browsers, terminals, etc.). The two main X Window systems are XOrg<\/a> and XFree86<\/a>.<\/p>\n

Linux has a system of runlevels, similar to the Windows concepts of recovery console, the various safe modes, and normal operation. For Linux, the runlevels are:<\/p>\n