Bootstrap – A Starter for the Impatient¶
Getting Help from Linux¶
Once you have Linux installed and running, the most important piece of information you need is how to get help. There are megabytes of documentation right there on your Linux system that can answer all of your questions, if you just know how to access it!
The standard way to get help, which works on any UNIX system, is a command called
man (think “manual”, as in user handbook). To get help on the
command, for example you would type:
This displays a help screen describing the program and its usage. Man pages, as
they are known, are formatted on the fly from special source files, and are
displayed using the pager program
less. You can scroll back and forth line by line with the arrow keys or whole
screens using the
PgDn keys. When you’re done reading,
press Q to quit (the
escape key will not get you out of
you’ll get back to the command prompt.
Man pages are stored in a categorized database. These are the standard categories:
- User Commands
- System Calls
- File Formats
- System Administration
Sometimes you will need to know this in order to find the man page you are
looking for. For example, there is a user command
passwd that can be used
to change your login password. If you type
man passwd you will get the
man page for this command, since it is in section 1. However, there is also a
passwd that stores the password database on your system. The
format for this file is explained in a man page in section 5, File Formats. To
get to it, you need to type
man 5 passwd so the man command will look
in section 5 rather than starting at section 1.
Man pages are often very detailed and might tell you far more than you wanted
to know. If you just want a quick idea of what a command does, use the
whatis command. For example,
whatis grep returns:
grep, egrep, fgrep (1) - print lines matching a pattern
This shows you that
grep, and its related commands
fgrep, have man pages in section 1, and are used to “print lines matching
a pattern.” If you were searching for a command to copy files, you would know
that this isn’t it and you could move on. Or you could consult the man page
for details on using these commands.
Related to the
whatis command is apropos, which searches the
whatis database for keywords. If you know what you want to do but don’t know
apropos will give you list of related commands. For example,
if you want to copy files, try
apropos copy and get:
bcopy (3) - copy byte strings copy (l) - copy data to/from a class from/to a Unix file. copysign (3) - copy sign of a number cp (1) - copy files cpio (1) - copy files to and from archives dd (1) - convert a file while copying it dvicopy (1) - produce modified copy of DVI file fcopy (n) - Copy data from one channel to another.
Your list will probably be much longer than this, but by reading through it
you will find that the command you want is
cp for copying files.
whatis commands don’t work on your system, it may
mean that the whatis database has not been created, or is corrupt. You can
rebuild it by running
/usr/sbin/makewhatis as SuperUser. Note that the
apropos command will
accept only one parameter. You cannot search for multiple keywords. If you
try, only the first will be used. The
whatis command will accept multiple
search words, but searches for them individually rather than as a group (in
other words, combining them with OR rather than AND).
Many of the utilities included with Linux, especially those created by the GNU Project, have documentation in the form of info pages. Info pages look similar to man pages, but there is a lot more to them. Like the man pages, info documents are intended to act as your online “manual”, your guide to the GNU/Linux system. But info documents are integrated with each other in a hypertext database that can be read like a book (it even has a table of contents) and accessed from your terminal.
Where both man pages and info pages exist, the info documentation is probably
more accurate. To get info on the
grep command, type:
The info viewer looks and behaves much like GNU Emacs. Most of the emacs key combinations will work in the info viewer. If you aren’t familiar with emacs, you should probably get familiar with it, as its control keys and syntax are inescapably emulated by hundreds of Linux programs. (See Editing Files with Emacs for a basic tutorial and list of commands).
Navigating info documentation isn’t terribly complicated, nor is it completely
intuitive. Thankfully, there is a self teaching tutorial included with the
package. At any time you can type a question mark (
Control-h to access a list of available commands, in case you need help
with the navigation keys. Typing
h by itself takes you to the info
tutorial, the first few pages of which should tell you all you need to know
for simple operation. The keys to remember are
SPACE to page forward,
DELETE to page backward, and
ENTER to activate a hyperlink.
(Links are normally preceded by an asterisk).
L takes you to the Last
node (page) visited, like the “Back” button in your web browser.
Similarities Between Linux and DOS¶
Comparing DOS & Windows to Linux¶
Despite what some folks will tell you, there is a lot of superficial similarity between DOS and Linux, and also between MS Windows and the X Window System. We can leverage the knowledge we already have to get up and running faster in Linux.
What’s The Same?¶
- Hierarchical Directory Structure:
DOS, Windows, and Linux all store information in files which are organized into directories (also called folders). Directories may contain files and other directories. Although, the commands differ, files and directories can be created, deleted, renamed, copied, moved and listed from the command prompt.
Start a program by typing its name at the command prompt.
Windows can be minimized, maximized, closed using buttons or menus.
Here are some major points you need to know:
- Linux is Case Sensitive!: To Linux, a capital letter is NOT the same as a lower case letter. The file Junk.txt is NOT the same file as junk.txt. Watch this carefully! It will cause you monstrous headaches!
- Linux is quiet: If a command succeeds, it will just drop you back at the command prompt without a status message. This can be confusing to new users.
- Linux does not confirm anything: In DOS or Windows, if you try to delete a file or folder it will ask for confirmation (“Are you sure you want to do that?”). Linux won’t ask, it’ll just do it. This makes it very easy to accidentally destroy a file, or the entire file system. Be SURE of what you type!
- Slashes: Linux uses a forward slash (/) wherever DOS would use a backslash (\). Linux uses a dash (-) to indicate command switches where DOS would use a slash (/).
- Search Path: DOS always checks the current directory first, then looks at the
PATH environment variable. Linux never looks in the current directory but
searches only the directories listed in PATH. To run a program in the current
directory you have to type
Some other major differences require deeper explanations:
Win/DOS to Linux Quick Reference¶
Below is a quick table roughly mapping Windows or DOS commands to their Linux equivalents. A more comprehensive reference may be added later. Remember that Linux is case sensitive!
|DOS/Windows Command||Linux Equivalent||What it does|
||Change file or directory attributes or permissions. Note that file attributes on DOS are completely different from permissions on Linux.|
||Change the current directory. Similar syntax.|
||Clear the terminal screen|
||Copy files. Similar syntax. Without the -i, cp will not prompt for destructive actions like file replacement. If the target exists, it is overwritten.|
||Delete files. Without the -i, rm will not ask for confirmation.|
||Delete a directory and all its contents, including subdirectories.|
||List the files in the current directory, or a named directory.|
||Create a new subdirectory. Similar syntax.|
||Display a summary of current memory usage and availability.|
||Display the contents of a file one page/screen at a time. The less utility allows scrolling back and forth.|
||Move a file.|
||Delete an empty subdirectory. Similar syntax.|
||Rename a file or folder.|
||Display the contents of a file.|
||Display the name and version of the OS kernel.|
To log out and return to the
Login: prompt, just type:
If you’re ready to turn off the computer, you need to instruct Linux to shut it down properly so that your files are not damaged. To turn off the power type:
shutdown -h now
To reboot the computer type:
shutdown -r now
Note, however, that the
shutdown command can only be run by the root user.
If you try to run it as a regular user, even using the
su command, you’ll
get the message:
shutdown: must be root.
On Linux systems, an alternative is to use the commands
power down the computer and
/sbin/reboot to reboot. These commands can be
run by regular users with the proper permissions. This is not universally
correct on UNIX systems, so it is recommended not to try this on non-Linux