+ To add user:

sudo adduser <username>

to add password for your user

sudo passwd <username>

+ How can i switch from one user to another one? In this example, i want to switch from one user to another one.

su <username>

and type in your password to login

after that, you will be at a ‘$’ prompt. type:

bash

to get to a normal prompt.

+ How can I delete a user?

sudo userdel <username>

To shutdown / poweroff Ubuntu Linux

Type the command:

sudo halt

OR

sudo shutdown -h now

OR

sudo shutdown -r now

OR

 sudo init 6

To reboot Ubuntu Linux

Type the command:

sudo reboot

More information can be found about these two commands by typing following commands (man page):

man reboot
man shutdown

Telnet is a user command and an underlying TCP/IP protocol for accessing remote computers. Through Telnet, an administrator or another user can access someone else’s computer remotely. On the Web, HTTP and FTP protocols allow you to request specific files from remote computers, but not to actually be logged on as a user of that computer. With Telnet, you log on as a regular user with whatever privileges you may have been granted to the specific application and data on that computer.

A Telnet command request looks like this (the computer name is made-up):

telnet namhuy.org

The result of this request would be an invitation to log on with a userid and a prompt for a password. If accepted, you would be logged on like any user who used this computer every day.

Telnet is most likely to be used by program developers and anyone who has a need to use specific applications or data located at a particular host computer.

Install telnetd server

$ sudo apt-get install telnetd

Restart inetd service:

$ sudo /etc/init.d/openbsd-inetd restart

You should now be able to telnet to the server from Windows or Linux desktop system to Ubentu Linux telnet server. Type the following command to connect to Telnet server:

$ telnet ubentu-linux-server-ip
$ telnet 192.168.1.200
$ telnet ubentu.mydomain.com

Install the CVS server:
sudo apt-get install cvsd

When prompted in the cvsd installation process for Repository, type in “/cvsrepo”.

Now that the cvsd installation in complete goto /var/lib/cvsd
or seeking for a change(or if there is a new version of cvs updated):

sudo cvsd-buildroot /var/lib/cvsd
If the folder cvsrepo does not exist, then create it ..
sudo mkdir cvsrepo
sudo chown -R cvsd:cvsd cvsrepo

and then initilize the repository
sudo cvs -d /var/lib/cvsd/cvsrepo init
create a user and password
sudo cvsd-passwd /var/lib/cvsd/cvsrepo +username
sudo vi //var/lib/cvsd/cvsrepo/CVSROOT/config
Change “SystemAuto=no”

Test

cvs -d :pserver:username@localhost:/cvsrepo login

cvs -d :pserver:username@localhost:/cvsrepo checkout .

Go to terminal and type “sudo gdmsetup”. You will get login window preferences. Select Security tab; check “Enable automatic Login” and select the user. You are done! Simple ha? But why there is no shortcut in the

Ipkungfu is available a the Ubuntu repositories. To install ubuntu,

# aptitude install ipkungfu

Ipkungfu should now be working.

After installing ipkungfu, type

# ipkungfu

to configure ipkungfu and answer “yes” if you are prompted.

At this point, if you connecting remotely via ssh, make sure you are not disconnected because by default, ipkungfu is blocking all incoming connections. If you are working directly at the terminal, then there’s no problem. Open the file /etc/ipkungfu/services.conf

and append ACCEPT beside the port that you want to open.

# Service Names and Protocols are lowercase, Targets are UPPERCASE.
#
# Example:
# ssh:22:tcp:ACCEPT
ftp-data:20:tcp
ftp:21:tcp
ssh:22:tcp:ACCEPT
telnet:23:tcp
smtp:25:tcp
domain:53:tcp
bootps:63:tcp
http:80:tcp:ACCEPT
pop3:110:tcp
auth:113:tcp
ntp:123:tcp
imap:143:tcp
https:443:tcp
imaps:993:tcp
pop3s:995:tcp
socks:1080:tcp
# Add your services below. The rule is:
# ServiceName:ServicePort:Protocol[:ACCEPT|DROP|REJECT|or any valid target)] # extra comments
#

The, save the file. In the example, I have allowed connection for ports 22 (SSH) and 80 (HTTP). Open the file

/etc/ipkungfu/ipkungfu.conf

and configure it based on your server’s setting and your preferred setting.

# =========================================================================
# $Id: ipkungfu.conf 57 2005-11-02 17:04:20Z s0undt3ch $
# =========================================================================
# Please read the README and FAQ for more information
# Some distros (most notably Redhat) don’t have
# everything we need in $PATH so we specify it here.
# Make sure modprobe, iptables, and route are here,
# as well as ordinary items such as echo and grep.

# Default is as shown in the example below.
#PATH=/sbin:/usr/sbin:/bin:/usr/bin:/usr/local/bin:/usr/local/sbin

# Set the path to ipkungfu’s runtime error log.
# Default: /var/log/ipkungfu.log
#IPKUNGFU_LOG=

# Your external interface
# This is the one that connects to the internet.
# Ipkungfu will detect this if you don’t specify.
EXT_NET=”eth0″
#EXT_NET=”eth1″
#EXT_NET=”ppp0″

# Your internal interfaces, if any. If you have more
# than 1 internal interface, separate them with
# spaces. If you only have one interface, put “lo”
# here. Default is auto-detected.
#INT_NET=”eth0″
#INT_NET=”eth1″
#INT_NET=”lo”

# IP Range of your internal network. Use “127.0.0.1″
# for a standalone machine. Default is a reasonable
# guess. Separate multiple ranges with spaces.
#LOCAL_NET=”192.168.0.0/255.255.0.0 10.0.0.0/255.0.0.0″

# Set this to 0 for a standalone machine, or 1 for
# a gateway device to share an Internet connection.
# Default is 1.
GATEWAY=0

# TCP ports you want to allow for incoming traffic
# Don’t add ports here that you intend to forward.
# This should be a list of tcp ports that have
# servers listening on them on THIS machine,
# separated by spaces. You can add port ranges
# delimited by hyphens, such as “20-22″. Default
# is none.
#ALLOWED_TCP_IN=”22 80″

# UDP ports to allow for incoming traffic
# See the comments above for ALLOWED_TCP_IN
#ALLOWED_UDP_IN=”"

# Temporarily block future connection attempts from an
# IP that hits these ports (If module is present)
# Hits to these ports will be logged as “BADGUY” hits
# regardless of log.conf settings.
FORBIDDEN_PORTS=”135 137 139″

# Drop all ping packets?
# Set to 1 for yes, 0 for no. Default is no.
BLOCK_PINGS=0

# Possible values here are “DROP”, “REJECT”, or “MIRROR”
#
# “DROP” means your computer will not respond at all. “Stealth mode”
#
# “REJECT” means your computer will respond with a
# message that the packet was rejected.
#
# “MIRROR”, if your kernel supports it, will swap the source and
# destination IP addresses, and send the offending packet back
# where it came from. USE WITH EXTREME CAUTION! Only use this if you fully
# understand the consequences.
#
# The safest option, and the default in each case,, is “DROP”. Don’t change
# unless you fully understand this.
# What to do with ‘probably malicious’ packets
#SUSPECT=”REJECT”
SUSPECT=”DROP”

# What to do with obviously invalid traffic
# This is also the action for FORBIDDEN_PORTS
#KNOWN_BAD=”REJECT”
KNOWN_BAD=”DROP”

# What to do with port scans
#PORT_SCAN=”REJECT”
PORT_SCAN=”DROP”

# How should ipkungfu determine your IP address? The default
# answer, “NONE”, will cause ipkungfu to not use the few
# features that require it to know your external IP address.
# This option is good for dialup users who run ipkungfu on
# bootup, since dialup users rarely use the features that
# require this, and the IP address for a dialup connection
# generally isn’t known at bootup. “AUTO” will cause
# ipkungfu to automatically determine the IP address of
# $EXT_NET when it is started. If you have a static IP
# address you can simply enter your IP address here.
# If you do port forwarding and your ISP changes your IP
# address, choose NONE here, or your port forwarding
# will break when your IP address changes. Default is
# “NONE”.
#GET_IP=”NONE”
#GET_IP=”AUTO”
GET_IP=”202.92.148.101″

# If the target for identd (113/tcp) is DROP, it can take
# a long time to connect to some IRC servers. Set this to
# 1 to speed up these connections with a negligible cost
# to security. Identd probes will be rejected with the
# ‘reject-with-tcp-reset’ option to close the connection
# gracefully. If you want to actually allow ident probes,
# and you’re running an identd, and you’ve allowed port
# 113 in ALLOWED_TCP_IN, set this to 0. Default is 0.
#DONT_DROP_IDENTD=0
# Set this to 0 if you’re running ipkungfu on a machine
# inside your LAN. This will cause private IP addresses
# coming in on $EXT_NET to be identified as a spoof,
# which would be inaccurate on intra-LAN traffic
# This will cause private IP addresses coming in on
# $EXT_NET to be identified as a spoof. Default is 1.
#DISALLOW_PRIVATE=1

# For reasons unknown to me, ipkungfu sometimes causes
# kernel panics when run at init time. This is my
# attempt to work around that. Ipkungfu will wait
# the specified number of seconds before starting, to
# let userspace/kernel traffic catch up before executing.
# Default is 0.
#WAIT_SECONDS=5

# This option, if enabled, will cause ipkungfu to set
# the default policy on all builtin chains in the filter
# table to ACCEPT in the event of a failure. This is
# intended for remote administrators who may be locked
# out of the firewall if ipkungfu fails. A warning to
# this effect will be echoed so that the situation can be
# rectified quickly. This is the same as running
# ipkungfu with –failsafe. Default is 0.
#FAILSAFE=0

# Configurable list of kernel modules to load at runtime.
# If no list is provided, the default and needed ones,
# ip_nat_irc, ip_conntrack_ftp ip_nat_ftp ip_conntrack_irc,
# will still be loaded.
#MODULES_LIST=”"

The

EXT_NET=”eth0″

is you the active network interface.

GATEWAY=0

because I’m configuring a standalone server. I have also set the forbidden ports

FORBIDDEN_PORTS=”135 137 139″

I don’t block pings

BLOCK_PINGS=0

because the ping tool is an effective use to test for the connectivity of the server.
For suspected, bad ports and port scan, I drop the packets.

SUSPECT=”DROP”
KNOWN_BAD=”DROP”
PORT_SCAN=”DROP”

If you have a static IP address, set GET_IP to your IP address.

GET_IP=”202.92.148.101″

The save the file. Restart by ipkungfu

/etc/init.d/ipkungfu restart

Upgrading to Ubuntu 7.10 now, before the rush
To upgrade to Ubuntu 7.10 now, before the rush, by following these instructions:

1. Open a terminal window (Applications -> Accessories -> Terminal)
2. Run the following command:

update-manager -d (after Oct 18th, remove the -d option)

This will upgrade to the release candidate, which is considered complete and stable. On Oct 18th, apply the updates and you will be running 7.10 final release.

Note: This works only if you are running Ubuntu 7.04. If you are running an older version apply the upgrades in steps (for example, Ubuntu 6.10 -> Ubuntu 7.04 -> Ubuntu 7.10) using the update-manager. Otherwise you may break your Ubuntu installation.

Installing Ubuntu 7.10 Release Canidate
If you are not running Ubuntu download the release canidate ISO image and install it:
http://releases.ubuntu.com/7.10/ubuntu-7.10-rc-desktop-i386.iso
or http://releases.ubuntu.com/7.10/ubuntu-7.10-rc-desktop-amd64.iso

After installing Ubuntu using the release canidate ISO, apply updates on Oct 18th and you will be running 7.10 final release.

Downloading Ubuntu 7.10 Final Release
If you want to wait until the final release is available:
Try downloading from an Ubuntu mirror
Download the torrent, watch LinuxTracker.org

sudo /usr/share/doc/libdvdread3/install-css.sh

In other distros the install-css.sh perhaps is inside the examples directory like this:

sudo /usr/share/doc/libdvdread3/examples/install-css.sh

sudo apt-get install rar
sudo ln -fs /usr/bin/rar /usr/bin/unrar

After that you can find Archive Manager in the Gnome menu under Applications -> Accessories.

apt-get install nmap