We will show you how adding a new sudoer is quickly done.
Open a Root Terminal and type visudo (to access and edit the list)
Using the up/down arrows, navigate to the bottom of the sudoers file that is now displayed in the terminal
Just under the line that looks like the following:
root ALL=(ALL) ALL
Add the following (replacing user with your actual username):
user ALL=(ALL) ALL
Now press Ctrl+X and press Y when promted to save
That's it, your new user now has root privileges!
Vim is an editor to create or edit a text file.
There are two modes in vim. One is the command mode and another is the insert mode.
In the command mode, user can move around the file, delete text, etc.
In the insert mode, user can insert text.
Changing mode from one to another
From command mode to insert mode type a/A/i/I/o/O ( see details below)
From insert mode to command mode type Esc (escape key)
Some useful commands for VIM
Text Entry Commands (Used to start text entry)
a Append text following current cursor position
A Append text to the end of current line
i Insert text before the current cursor position
I Insert text at the beginning of the cursor line
o Open up a new line following the current line and add text there
O Open up a new line in front of the current line and add text there
The following commands are used only in the commands mode.
Cursor Movement Commands
h Moves the cursor one character to the left
l Moves the cursor one character to the right
k Moves the cursor up one line
j Moves the cursor down one line
nG or :n Cursor goes to the specified (n) line
(ex. 10G goes to line 10)
^F (CTRl F) Forward screenful
^B Backward screenful
^f One page forward
^b One page backward
^U Up half screenful
^D Down half screenful
$ Move cursor to the end of current line
0 (zero) Move cursor to the beginning of current line
w Forward one word
b Backward one word
Exit Commands
:wq Write file to disk and quit the editor
:q! Quit (no warning)
:q Quit (a warning is printed if a modified file has not been saved)
ZZ Save workspace and quit the editor (same as :wq)
: 10,25 w temp
write lines 10 through 25 into file named temp. Of course, other line
numbers can be used. (Use :f to find out the line numbers you want.
Text Deletion Commands
x Delete character
dw Delete word from cursor on
db Delete word backward
dd Delete line
d$ Delete to end of line
d^ (d caret, not CTRL d) Delete to beginning of line
Yank (has most of the options of delete)-- VI's copy commmand
yy yank current line
y$ yank to end of current line from cursor
yw yank from cursor to end of current word
5yy yank, for example, 5 lines
Paste (used after delete or yank to recover lines.)
p paste below cursor
P paste above cursor
"2p paste from buffer 2 (there are 9)
u Undo last change
U Restore line
J Join next line down to the end of the current line
File Manipulation Commands
:w Write workspace to original file
:w file Write workspace to named file
:e file Start editing a new file
:r file Read contents of a file to the workspace
To create a page break, while in the insert mode, press the CTRL key
And l. ^L will appear in your text and will cause the printer to start
A new page.
Other Useful Commands
Most commands can be repeated n times by typing a number, n, before
the command. For example 10dd means delete 10 lines.
. Repeat last command
cw Change current word to a new word
r Replace one character at the cursor position
R Begin overstrike or replace mode – use ESC key to exit
:/ pattern Search forward for the pattern
:? pattern Search backward for the pattern
n (used after either of the 2 search commands above to
continue to find next occurrence of the pattern.
:g/pat1/s//pat2/g replace every occurrence of pattern1 (pat1) with
pat2
Example :g/tIO/s//Ada.Text_IO/g
This will find and replace tIO by Ada.text_IO everywhere in the file.
:g/a/s// /g replace the letter a, by blank
:g/a/s///g replace a by nothing
note: Even this command be undone by u
Examples
Opening a New File
Step 1 type vim filename (create a file named filename)
Step 2 type i ( switch to insert mode)
Step 3 enter text (enter your Ada program)
Step 4 hit Esc key (switch back to command mode)
Step 5 type :wq (write file and exit vim)
Editing the Existing File
Step 1 type vim filename (edit the existing file named filename)
Step 2 move around the file using h/j/k/l key or any appropriate command
h Moves the cursor one character to the left
l Moves the cursor one character to the right
k Moves the cursor up one line
j Moves the cursor down one line
nG or :n Cursor goes to the specified (n) line
(ex. 10G goes to line 10)
Step 3 edit required text (replace or delete or insert)
Step 4 hit Esc key (exit from insert mode if you insert or replace text)
Step 5 type :wq
Screen is like a window manager for your console. It will allow you to keep multiple terminal sessions running and easily switch between them. It also protects you from disconnection, because the screen session doesn’t end when you get disconnected.
You’ll need to make sure that screen is installed on the server you are connecting to. If that server is Ubuntu or Debian, just use this command:
sudo apt-get install screen
Now you can start a new screen session by just typing screen at the command line. You’ll be shown some information about screen. Hit enter, and you’ll be at a normal prompt.
To disconnect (but leave the session running)
Hit Ctrl + A and then Ctrl + D in immediate succession. You will see the message [detached]
To reconnect to an already running session
screen -r
To reconnect to an existing session, or create a new one if none exists
screen -D -r
To create a new window inside of a running screen session
Hit Ctrl + A and then C in immediate succession. You will see a new prompt.
To switch from one screen window to another
Hit Ctrl + A and then Ctrl + A in immediate succession.
To list open screen windows
Hit Ctrl + A and then W in immediate succession
There’s lots of other commands, but those are the ones I use the most.
If you are running Ubuntu and want to use the Tomcat servlet container, you should not use the version from the repositories as it just doesn’t work correctly. Instead you’ll need to use the manual installation process that I’m outlining here.
Before you install Tomcat you’ll want to make sure that you’ve installed Java. I would assume if you are trying to install Tomcat you’ve already installed java, but if you aren’t sure you can check with the dpkg command like so:
dpkg –get-selections | grep sun-java
This should give you this output if you already installed java:
sun-java6-bin install
sun-java6-jdk install
sun-java6-jre install
If that command has no results, you’ll want to install the latest version with this command:
sudo apt-get install sun-java6-jdk
Installation
Now we’ll download and extract Tomcat from the apache site. You should check to make sure there’s not another version and adjust accordingly.
wget http://apache.hoxt.com/tomcat/tomcat-6/v6.0.14/bin/apache-tomcat-6.0.14.tar.gz
tar xvzf apache-tomcat-6.0.14.tar.gz
The best thing to do is move the tomcat folder to a permanent location. I chose /usr/local/tomcat, but you could move it somewhere else if you wanted to.
sudo mv apache-tomcat-6.0.14 /usr/local/tomcat
Tomcat requires setting the JAVA_HOME variable. The best way to do this is to set it in your .bashrc file. You could also edit your startup.sh file if you so chose.
The better method is editing your .bashrc file and adding the bolded line there. You’ll have to logout of the shell for the change to take effect.
vi ~/.bashrc
Add the following line:
export JAVA_HOME=/usr/lib/jvm/java-6-sun
At this point you can start tomcat by just executing the startup.sh script in the tomcat/bin folder.
Automatic Starting
To make tomcat automatically start when we boot up the computer, you can add a script to make it auto-start and shutdown.
sudo vi /etc/init.d/tomcat
Now paste in the following:
# Tomcat auto-start
#
# description: Auto-starts tomcat
# processname: tomcat
# pidfile: /var/run/tomcat.pidexport JAVA_HOME=/usr/lib/jvm/java-6-sun
case $1 in
start)
sh /usr/local/tomcat/bin/startup.sh
;;
stop)
sh /usr/local/tomcat/bin/shutdown.sh
;;
restart)
sh /usr/local/tomcat/bin/shutdown.sh
sh /usr/local/tomcat/bin/startup.sh
;;
esac
exit 0
You’ll need to make the script executable by running the chmod command:
sudo chmod 755 /etc/init.d/tomcat
The last step is actually linking this script to the startup folders with a symbolic link. Execute these two commands and we should be on our way.
sudo ln -s /etc/init.d/tomcat /etc/rc1.d/K99tomcat
sudo ln -s /etc/init.d/tomcat /etc/rc2.d/S99tomcat
Tomcat should now be fully installed and operational. Enjoy!
When you are using a linux system, it’s useful to find out what groups you belong to, so you can understand whether you have access to files and directories. This is one of the simplest commands possible. I’m using Ubuntu linux, but this command should work on most varieties of linux.
Quotationgroups <username>
If you don’t enter a username, it defaults to your own username. For instance:
Quotationgeek@ubuntuServ:$ groups
geek adm dialout cdrom floppy audio dip video plugdev lpadmin scanner admin fuse
You can also check the groups for any other user, including root:
Quotationgeek@ubuntuServ:$ groups root
root : root fuse
