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Author Topic: Linux Tutorial 6 - Questions which beginners ask  (Read 9272 times)


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Linux Tutorial 6 - Questions which beginners ask
« on: December 16, 2007, 03:26:15 PM »

This is the sixth in the series of tutorials. Here we try to answer some of the questions which puzzle newcomers to Linux.

Why do I keep on getting asked for a password?

In Linux there is a clear distinction between users and the administrator (root). This is one of the basic planks of the security provisions in Linux. Every file in the system has an owner, and a set of associated permissions which define who can do what with the file. All the system files are owned by root, and only root can modify or delete them.

Normally you should log on using your user name, and this gives you limited permission to change things. The only files which you can modify are those in your own home directory, and those in the /tmp directory which have been written by programs which you have been running. This is all the permission you need to do the normal 'user' things (i.e. run programs).

However, when you want to do some administration, such as installing or removing software or hardware, you need to have root permission, and this is where the passwords come in. If you run the package manager (e.g. Synaptic) for example, a box pops up asking you to enter the root password. After entering this you have full root permission, but only within the context of that program - you're still logged on as a normal user, and any other programs which you left running still only have user level permission. When you exit from the administrative program, all root permission is removed again.

This often seems irksome to newcomers, but it's a big part of the reason why Linux is a much more difficult target for viruses and crackers. It also protects you from the possibility of accidentally damaging your system by typing an incorrect command. You could subvert this behaviour by always logging on as root, but you are strongly advised not to do this. You soon get used to entering the root password when needed, and there's a big security benefit in doing so.

Where is my C drive?

Linux doesn't use drive letters, so there isn't a C drive, or D or E, etc. All filesystems (hard disk partitions, optical drives, floppy drives, USB memory sticks, etc.) are incorporated into a single directory hierarchy. Each filesystem is mounted to a specific directory. 'Mounted' means that a directory in the system is allocated to the particular filesystem, and all its files are to be found under that directory, which is called the 'mount point'. Mount points can in principle be anywhere in the system, not just at the top level.

There is always one filesystem mounted at the top level, commonly called the root level but not to be confused with root the administrator. It's quite common, but not universal, to have a separate hard disk partition mounted at /home which is where all the users' private files are kept. Removable media such as optical drives and floppies are usually mounted to subdirectories under /media. See The Linux filesystem hierarchy for more information.

I'm confused by forward slashes and backslashes in directory paths

Linux was very much inspired by Unix, which existed long before Windows. Unix uses the forward slash (/) as its directory separator, and so does Linux. The internet of course also uses / because the vast majority of internet servers run Unix or Linux. Windows chose a different route for historical reasons. You'll soon get used to using /.

How do I defrag my hard disk?

The short answer is that you don't. Linux filesystems use smart techniques for placing files on disks, so that they never get seriously fragmented. The only warning here is that you shouldn't allow your disks to get too full, because the techniques which are used need some spare space on the disks in order to do their job. But in any case, defrag utilities need some spare space too, so you shouldn't let your disks get too full on any system.

Linux defrag utilities do exist, but very few people use them. For the majority of people, it simply isn't worth bothering about.

Why Linux doesn't need defragmenting

What anti-virus program should I use?

Linux is a more difficult target for viruses than Windows, and at the time of writing (end 2007) no damaging viruses have been seen. That doesn't mean it won't happen of course, and Linux anti-virus programs exist for the more prudent to use. If your Linux machine is connected to a Windows machine you should certainly consider anti-virus protection so as to avoid being an entry route for Windows viruses.

AVG Free and McAfee Antivirus (commercial) are available in Linux versions, and Clamav is a respected open source anti-virus kit. Clamav is a command-line tool, but there is a GUI front end for it called Klamav, and both of these should be available to install using your package manager.

Do I need a firewall?

Linux has a built-in firewalling system called IPTables, but this is quite complicated to configure manually. However most modern distributions will have GUI setup utilities available for installation, and these are quite straightforward to use. Typical examples are Guarddog and Firestarter. Some distributions (e.g. PCLinuxOS, Mandriva and OpenSuse) include their own custom firewall setup programs as part of their 'control panels'. Many distributions configure a basic desktop firewall as part of the installation.

If your access to the internet is via a router, this will almost certainly contain its own firewall, and for most people this should be quite sufficient (although it's worth checking that it doesn't leave ports open by default).

Where do I go for information if I'm stuck?

There's a truly vast amount of published information about Linux, but it's all over the place. If you Google for a particular problem it's virtually certain that you'll find discussions about it, but the sheer volume of information can be overwhelming.

In general, the best place to start will be the support forum(s) for the distribution which you're using. These are mostly quite friendly places, but do read the forum rules before you start asking questions.

Other useful sources are:
The Linux Foundation - Printing
Linux scanner information
Video For Linux

[Edited to change link to filesystem hierarchy standard]