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Posts Tagged ‘LINUX’

Aug 14
2009

Ubuntu: Change menu order in GRUB loader

Last updated: August 14th, 2009

GRUB stands for GRand Unified Bootloader. This is to enable the listing of multiple operating systems so the users could choose the OS of their choice.

To change the menu order we need to edit a file called menu.lst

# vi /boot/grub/menu.lst

Look for a line “default 0“. This is the option to indicate that the first menu on the list should be loaded by default. In order for you to set the default menu content in the GRUB loader that needs to get started you can set this parameter.

This is of the form “default <ID>” where ID = N -1. If there are 4 list items in the menu and if you want to load the 4th item by default, you need to set this configuration setting to “default 3″.

Another option for you is to have the menu list with the entry “savedefault = true“. This would enable the last used menu entry to get loaded during the next boot.

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Posted in LINUX, Tips, Tricks, Guides | 1 Comment »

Jul 26
2009

Linux: How to change the default Run Level?

Last updated: July 22nd, 2009

To list the current run level
$ who -r
run-level 5 2008-07-22 21:35 last=5

To change the default Run level edit /etc/inittab

You can also switch to another run level number by issuing
$ init

For example,
$ init 3

Now the system switches from Run level 5 to Run level 3

To list the current run level
$ who -r
run-level 3 2008-07-22 22:35 last=5

In the above result notice the last part which states “last=5″. This indicates that the last run level was 5

When the system is running and if we want to apply patches or alter certain configurations, the above command comes in handy.

The other option to change the current level is
$ telinit <run level number>

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Posted in LINUX, Linux Server, Tips, Tricks, Guides | 1 Comment »

Jul 25
2009

Linux: How to find the current Run Level?

Last updated: July 25th, 2009

Default init level is set in /etc/inittab.

$ cat /etc/inittab (to display the init levels)

Inside that file, you can note a line which will state the run level number like
id:5:initdefault: (indicating run level 5 which means that the system is running with x windows)

To find the current run level you can execute the following commands

$ who -r
run-level 5 2008-07-22 21:35 last=5
which indicates that the system is in run-level 5

Other option to find the run level is
$ /sbin/runlevel
N 5

To find out what sub processes are associated with each run level you can go to
$ cd /etc/rcN.d/ (Where N denotes the run level number)

For example
$ cd /etc/rc1.d/
$ ls -l
This will list symbolic links to various processes associated with run level 1.

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Posted in LINUX, Linux Server, Tips, Tricks, Guides | 1 Comment »

Jul 23
2009

Linux: How many Run Levels are there and what are they?

Last updated: July 22nd, 2009

Linux systems have 7 Run Levels and they are as follows.

0 – system halt
1 – single user mode (system maintenance mode)
2 – multiuser mode without network access
3 – full multiuser mode with network access
4 – not used
5 – multiuser mode with X windows
6 – reboot or restart

Each run level in linux has a very specific purpose.

Run level 1 is also known as system maintenance mode and at this level the system prompt appears without root level password. It should be used only when it is absolutely necessary for system maintenance.

Run level 4 is not used and it can be used by the user to customize his own level.

Note: Solaris Run Level is different from Linux run levels.

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Posted in LINUX, Linux Server, Tips, Tricks, Guides | No Comments »

Jul 22
2009

Linux: What is Run Level?

Last updated: July 22nd, 2009

Run Level is a term to indicate your computer’s state of operation. When your computer starts it initially starts the the first process called the init process. Init process in turn starts associated sub-processes for that state of operation.

Run Level is the state of the machine – indicating the processes and sub-processes that needs to be started in order for the Operating System to be in that state.

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Posted in LINUX, Linux Server | No Comments »

Jul 15
2009

How to display the history of commands executed by the user?

Last updated: July 15th, 2009

Linux: History command

Each bash sessions stores the history of commands executed in .bash_history file which in turn in stored under each user’s home directory

usr100@dev01:/tmp/user$ ls
07-14.txt a.txt b.txt d.txt

usr100@dev01:/tmp/user$ cat ~/.bash_history
clear
su root
rm -i d.txt
ls -ltr
touch c.txt

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Posted in Linux Server, Tips, Tricks, Guides | No Comments »

Jul 13
2009

How to restrict folder, file permission settings for each user?

Last updated: July 13th, 2009

Sticky bit

There may be situation where you wanted all users to store files in a certain folder but might want to restrict users from deleting other users file. For this scenario, you can set the sticky bit of the folder which will serve our purpose.

For example we have created a folder inside /tmp directory called “user”

root@dev:/tmp# ls -l | tail -1
drwxr-xrwx 2 root root 4096 2009-07-13 11:39 user
root@dev:/tmp# cd user

Now create a file called a.txt (you are currently with root privileges)
root@dev:/tmp/user# touch a.txt

Now change to the user with normal privileges (i have created a user called ‘usr100′ for this purpose)
usr100@dev:/tmp/user$ su usr100
password:
usr100@dev:/tmp/user$ whoami
usr100
(more…)

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Posted in LINUX, Security, Tips, Tricks, Guides | No Comments »

May 07
2009

How to configure Tomcat in Ubuntu?

Last updated: May 6th, 2009

Configuring Tomcat in Ubuntu with Apache server running on it

Login with the root account. Check if java is already installed on the machine. If not, first install java on ubuntu.

Web get the apache-tomcat tar file from the below location
(more…)

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Posted in Apache, LINUX, Linux Server | No Comments »

Apr 13
2009

Free Cryptography Tools

Last updated: April 13th, 2009

Following are the listing of tools that can be used for various purposes in Linux, Windows environments and those which are available FREE of cost for downloads. This is the first compilation and will continue to grow as time progresses. (more…)

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Posted in Security | No Comments »

Mar 06
2009

MySQL Case Sensitivity

Last updated: March 10th, 2009

Is MySQL Case-Sensitive?
The SQL syntax is NOT case-sensitive in MySQL.

If the application written in PHP/Perl or other languages were to be used in Microsoft & Linux environment, then it would really be an issue for the database administrators and for the programmers.

That is the reason why you might have noticed books or sites saying that it is always recommended to treat MySQL syntax as being case-sensitive.

It was interesting to learn that the database name remains case sensitive.

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Posted in MySql | No Comments »

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