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tutorial - Reinstall Ubuntu Grub Bootloader

1) Boot with the LiveCD

2) Open a Terminal and type in the following commands, note that hd0,0 implies the first hard drive and the first partition on that drive, which is where you probably installed grub to during installation. If not, then adjust accordingly.

sudo grub
> root (hd0,0)
> setup (hd0)
> exit

Reboot (removing the livecd), and your boot menu should be back.

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source:http://linuxpoison.blogspot.com/2008/06/135781758013245.html

tutorial - Installing Fedora from the hard drive (without a boot CD).

Download the DVD ISO :

Get the Fedora Core DVD iso from http://fedoraproject.org/en/get-fedora and save the disk image to a partition on your hard drive that will not be formatted during the installation.

If you have a FAT32 partition that you use to share data with Windows on a dual boot system like mine then this is an ideal place. Otherwise any Linux partition (ext2, ext3) will do as long as it can be read by the installation program (for this reason an NTFS formatted windows partition will not work).

Also make sure that the partition is large enough to hold the file as the Fedora DVD weights in around 3+ Gb.

Mount the downloaded iso file

Next we need to mount the iso so we can read the contents, open a terminal and as root run the following command. The iso can be mounted anywhere but in my case I'll create a folder in my home directory and mount it there.

$ mkdir ~/FedoraInstall
$ mount -o loop -t iso9660 /mnt/fat/dualboot/F-9-i386-DVD.iso FedoraInstall/

Replace /mnt/fat/dualboot/F-9-i386-DVD.iso with the location of your saved DVD iso file and FedoraInstall with your desired mount point. Now you should be able to browse the contents of the install iso from the command line or Nautilus.

Copy the boot files

Next go into the newly created mounted files and find the directory called isolinux, From the command line do the following.

$ cd ~/FedoraInstall/isolinux/
$ ls
boot.cat initrd.img memtest rescue.msg vmlinuz
boot.msg isolinux.bin options.msg splash.lss
general.msg isolinux.cfg param.msg TRANS.TBL

Copy the files called initrd.img and vmlinuz to your /boot directory (you will need to be root to write files to the boot directory)

$ cp initrd.img vmlinuz /boot/

If you wish to rename these files to make them easier to identify in the future that's OK as long as you know what they are called for the next step. I'll rename them with the name -installFC8, again root login is required.

$ cd /boot/
$ mv initrd.img initrd-installFC8.img
$ mv vmlinuz vmlinuz-installFC8

Edit your grub.conf

Finally we need to add an entry to our grub.conf file to give us the option of booting into the installer and to tell grub where to find the boot files we just copied. Open the file /etc/grub.conf with a text editor (as root) and add the following lines.

title Fedora 9 install
root (hd0,2)
kernel /vmlinuz-install ro
initrd /initrd-install.img

The title is up to you but be sure to replace the root (hd0,2) with the correct information from your system. The easiest way is just to copy the entry from your other grub entries. In my case I also have:

title Fedora (2.6.24.1-41.fc8)
root (hd0,2)
kernel /vmlinuz-2.6.22.1-41.fc8 ro root=/dev/VolGroup00/LogVol00 quiet vga=834

So just use the value from your other boot target. Also if you renamed the initrd.img and vmlinuz files use the names that apply to you. Save and close the file.

Reboot into the installer.

Next reboot your computer and from the list of boot targets select the 'Fedora 9 install' entry. The installer will then run presenting you with a screen first asking for your language and keyboard layout.

The next screen asks for the install source, select 'Hard Drive' from the list. From the screen shown below select the partition on your hard drive that contains the Fedora iso you downloaded along with the directory containing the image (as instructed you can press F2 here to
browse for the iso file).

Thanks to : http://bobpeers.com/

source:http://linuxpoison.blogspot.com/2008/06/135781758012203.html

tutorial - World's fastest supercomputer runs RedHat Linux

IBM announced the completion of a one-petaflop supercomputer that runs Red Hat Linux. Twice as fast as the previous record-setter, the IBM Blue Gene, the Roadrunner uses a hybrid design that combines 6,948 dual-core AMD Opteron chips with 12,960 Cell processor engines.

The Roadrunner was built for the Department of Energy's National Nuclear Security Administration and will be soon be shipped to its new home at Los Alamos National Laboratory in New Mexico. There, it will be put to work monitoring the nation's nuclear weapons stockpile, but will also be available for research into astronomy, energy, human genome science, and climate change, says IBM.

Like Blue Gene and some 75 percent of the world's supercomputers, the $100 million Roadrunner runs Linux. As with most of them, the new world record-holder runs multiple instances of Linux over a cluster of interconnected computers.

More

source:http://linuxpoison.blogspot.com/2008/06/13578175804559.html

tutorial - How To install RMP packages in Ubuntu

There's a utility called Alien that converts packages from one format to the other. This doesn't always mean that an rpm will work on your system, though. You will need to install some prerequisite software packages in order to install alien

Run this command to install alien and other necessary packages:

sudo apt-get install alien dpkg-dev debhelper build-essential

To convert a package from rpm to debian format, use this command syntax. The sudo may not be necessary, but we'll include it just in case.

sudo alien packagename.rpm

To install the package, you'll use the dpkg utility, which is the internal package management tool behind debian and Ubuntu.

sudo dpkg -i packagename.deb

The package should now be installed, providing it's compatible with your system.

Thanks to : http://www.howtogeek.com

source:http://linuxpoison.blogspot.com/2008/06/135781758017380.html

tutorial - What is Challenge Handshake Authentication Protocol (CHAP)

Approaches to authentication such username and password is done only once, at the point that the user logs into the system. An alternative to this approach is provided by the Challenge Handshake Authentication Protocol (CHAP) which repeats an authentication procedure at random intervals during an ongoing connection between a client and a service.

The CHAP authentication scheme is used primarily by Point to Point Protocol (PPP) servers as a way to validate the identity of remote clients (perhaps most commonly used by internet service providers). At random time intervals, CHAP verifies the identity of the client by using something known as a three-way handshake. This verification is performed using a credential which is known to both the client and the service (typically the user's password).

After the link between the client and the server (also known as the authenticator) has been established it sends a challenge message to the peer. The peer subsequently responds to the authenticator with a hashed value calculated using the Message Digest (MD5) hashing algorithm. The authenticator checks the client response against its own calculation of the expected hash value. If the two values match, the authenticator acknowledges the authentication. If the values do not match, the connect is terminated. These steps are repeated at random intervals.

It is important to note that Microsoft has also implemented two variants of the Challenge Handshake Authentication Protocol, called MS-CHAP and MS-CHAP-v2.

source:http://linuxpoison.blogspot.com/2008/06/135781758012352.html

tutorial - HowTo do X11 Forwarding over an SSH connection

Starting an X11 session over an SSH connection is as easy as connecting to the SSH server, we just need to use the -Y option and running an X program on a local machine.

ssh -Y @example.com

When an X program is run from the secure shell prompt, the SSH client and server create a new secure channel, and the X program data is sent over that channel to the client machine transparently.

source:http://linuxpoison.blogspot.com/2008/06/13578175807661.html

tutorial - HowTo solve the problem of apache/sendmail hangs During Startup

If you are having trouble with the Apache-based httpd service or Sendmail hanging at startup, make sure the following line is in the /etc/hosts file:

127.0.0.1  localhost.localdomain  localhost

source:http://linuxpoison.blogspot.com/2008/06/135781758016066.html

tutorial - Limit users access to a time range

In the cases when you want to limit the access to a Linux operating system in a time range, you would like to use pam_time.so.

Take a look at /etc/security/time.conf

To limit for example ssh access from 23:00 PM and 08:00 AM.
sshd;*;*;!Al2300-0800

The format of the file is:
Service;ttys;users;time

the !Al means, anything except "All the days".

If you would like to permit people from 4 to 8 PM all the days, except root:
login;*;!root;!Al1600-2000

Further reading: man time.conf

source:http://linuxpoison.blogspot.com/2008/06/135781758010322.html

tutorial - Execute a task ‘at’ the time you want

Procedure :

At the prompt type this command followed by

$ at 2359

The moment you press Enter the prompt changes into an arrow indicating that more information is required by Linux. Type the following command assuming you have installed XMMS player which plays mp3 files and that you actually have a mp3 file in the directory shown below

> xmms /home/david/mp3s/rock_my_world.mp3

Once you have typed the above press and then finally press -D

Thats it. Now Linux will make the XMMS player to play the particular mp3 file at the time 23:59. Thats just a minute before midnight. Linux surely rocks your world !! ;-)

Basically if you are using the 24 hour clock then you enter the time you want with the hours and the minutes together one after another. Hours = 0-23 & Minutes = 0-59. Then type the exact command that you would have typed had you wanted to execute the task manually. If you want you can issue more commands after the first one. Once you finish entering all the tasks press -D to indicate that you have finished. Then wait and enjoy.. Linux will do the rest.

source:http://linuxpoison.blogspot.com/2008/06/13578175802664.html

tutorial - Monitor your hardware Temperature - Ubuntu

Computer Temperature Monitor is a little applet for the GNOME desktop that shows the temperature of your computer CPU and disks on screen. It allows you to log temperatures to a file. You can set alarms to notify you when a tempertature is reached.

Download (ubuntu): Here

Download (Source): Here

Configuration on Ubuntu:

source:http://linuxpoison.blogspot.com/2008/06/135781758016368.html

tutorial - Couple of easy steps to Speed Up Linux

By default there are lot of services that are running on your system (Any Fedora system) and all these services consume your resource like CPU and Memory, increase your booting time and also open your system for attack, So in order to make your system run faster and safer we need to stop all these unwanted services.

Login with root account, go to console and fire command “ntsysv”, you should see something similar to this…

Now stop all the unwanted services and restart your box, you should see some decrease in your booting time.

Note: If your not aware of what all these services means, please do some google or use command “system-config-services” which provides a good looking GUI interface and also provide some short description about all these services.

For suse use - They can use "yast2" to lookup the services.

2) Need to get more out of your linux
As per man pages of “mount” command, we have some good option to speed up the access of files from your HDD … “noatime option do not update inode access times on file system (e.g, for faster access on the news spool to speed up news servers)”So if we update the our fstab file and mount our root partition (/) with “noatime” will surely increase the speed of our box, (This is how you can do this - have similar entry for your “/” partition in your fstab file)

LABEL=/ / ext3 defaults,noatime 1 1

source:http://linuxpoison.blogspot.com/2008/06/13578175804721.html

tutorial - What is TTL - "Time To Live"

Have you ever observed the output of ping command … and wonder what’s this “TTL” stand for

Pinging www.google.com [72.14.205.104] with 32 bytes of data:

Reply from 72.14.205.104: bytes=32 time=365ms TTL=242
Reply from 72.14.205.104: bytes=32 time=367ms TTL=242
Reply from 72.14.205.104: bytes=32 time=370ms TTL=242
Reply from 72.14.205.104: bytes=32 time=366ms TTL=242

Each IP packet has a Time to Live (TTL) section that keeps track of the number of network devices the packet has passed through to reach its destination. The server sending the packet sets the initial TTL value, and each network device that the packet passes through then reduces this value by 1. If the TTL value reaches 0, the next network device will discard the packet.

This mechanism helps to ensure that bad routing on the Internet won’t cause packets to aimlessly loop around the network without being removed. TTLs therefore help to reduce the clogging of data circuits with unnecessary traffic.

source:http://linuxpoison.blogspot.com/2008/06/135781758012443.html

tutorial - Few Quick How To’s for Fedora

How to list partition tables
fdisk -l

How to list filesystem disk space usage
df -T -h

How to list mounted devices
mount

How to list PCI devices
lspci or /sbin/lspci
If the first does not work try the latter.

How to list USB devices
lsusb

How to forcefully unmount CD/DVD-ROM manually
umount /media/cdrom0/ -l

How to remount /etc/fstab without rebooting
mount -a

How to generate MD5 checksum files
md5sum file.iso > file.iso.md5

How to check MD5 checksum of files
e.g. Assumed that file.iso and file.iso.md5 are in the same folder
md5sum -c file.iso.md5

How to mount/unmount Image (ISO) files without burning
mkdir /media/iso
modprobe loop
mount file.iso /media/iso/ -t iso9660 -o loop
umount /media/iso/

How to change computer name
hostname your_new_computer_name

How to access network folders without mounting
e.g. Assumed that network connections have been configured properly
Network computer’s IP: 192.168.0.1
Shared folder’s name: linux
smb://192.168.0.1/linux

How to connect into remote Fedora desktop
e.g. Assumed that remote Fedora machine have configured Remote Desktop
Remote Fedora machine: 192.168.0.1
vncviewer -fullscreen 192.168.0.1:0

How to install support for NTFS
yum -y install kernel-module-ntfs-$(uname -r)

How to disable history listing in Console mode
rm -f $HOME/.bash_history
touch $HOME/.bash_history
chmod 000 $HOME/.bash_history

How to use Fedora Installation CD, to gain root user access
Insert Fedora CD #1 into your CD-ROM and boot from it
linux rescue

How to restart GNOME/KDE without rebooting computer
Press ‘Ctrl + Alt + Backspace’

How to switch to Console mode in GNOME/KDE
Press ‘Ctrl + Alt + F1′ (F2 - F6)
To switch back to GNOME/KDE modePress ‘Alt + F7′

How to install/uninstall .rpm files
To install .rpm filerpm -i package_file.rpm
To uninstall .rpm filerpm -e package_name

How to set System-wide Environment Variables
cp /etc/bash.bashrc /etc/bash.bashrc_backupg
edit /etc/bash.bashrc
Append the System-wide Environment Variables at the end of file and save.

How to save “man” outputs into files
man command | col -b > file.txt

How to convert Wallpaper to Splash Image for GRUB menu
convert -resize 640×480 -colors 14 wallpaper.png
splashimage.xpm && gzip splashimage.xpm

source:http://linuxpoison.blogspot.com/2008/06/13578175808877.html

tutorial - cachemgr (Cache Manager) configuration for Squid

The cache manager (cachemgr.cgi) is a CGI utility comes with squid for displaying statistics about the squid process as it runs. The cache manager is a convenient way to manage the cache and view statistics without logging into the server

To make this configuration you need a webserver (Apache) running and configured.

1) Try to locate your cachemgr.cgi file which comes with the squid package, this can be done using rpm -ql command (different distro stores this file at different location), here you can also use locate/find command.

# rpm -ql squid | grep cachemgr.cgi
/usr/share/doc/packages/squid/scripts/cachemgr.cgi
/usr/share/man/man8/cachemgr.cgi.8.gz

In this case my cachemgr.cgi is in /usr/share/doc/packages/squid/scripts/ directory

2) Copy cachemgr.cgi file to your configure script alias (/var/www/cgi-bin) directory of you Apache

3) Open squid.conf file and insert following two parameters at the end of the file

cache_mgr nikesh@domain.com
cachemgr_passwd your_Password all

4) Restart your squid and open your browser and type
http://localhost/cgi-bin/cachemgr.cgi
you should see something like … , provide a configure e-mail and password (mentioned above)

source:http://linuxpoison.blogspot.com/2008/06/13578175802376.html

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