First find the path of binary and configuration files, following is my example:
grep sudoers /var/sadm/install/contents
/opt/sfw/etc/sudoers f none 0440 root root 589 50133 1104945433 SFWsudo /opt/sfw/man/man4/sudoers.4 f none 0444 root bin 57547 31697 1104945433 SFWsudo /usr/local/share/vim/vim73/ftplugin/sudoers.vim f none 0644 bin bin 426 36373 1285497623 SMCvim /usr/local/share/vim/vim73/syntax/sudoers.vim f none 0644 bin bin 19276 64681 1285497623 SMCvim
Now my I can see that my configuration file i.e. sudoers is in /opt/sfw/etc/sudoers and for sudo it is always in the same path but in /bin directory i.e. /opt/sfw/bin/sudo
Steps for sudo to work properly:
Add /opt/sfw/bin in your PATH if it is not available – check with echo $PATH
Sudoers file default permission will be read only, for making changes you will need to first change the permission of sudoers file and edit your changes and revert back the permission of sudoers file to (chmod 440)
Sudo binary which is in /opt/sfw/bin should have the sticky bit set permission i.e. (chmod u+s )
Install three packages telnet-server, telnet and xinetd.
Make sure that the xinetd service should be running.
Configure the file name /etc/xinetd/telnet
1.) Install three packages telnet-server, telnet and xinetd.
You need to install three services
for example # yum install telnet-server telnet
the above command will also install the xinetd service. See the following example for reference:
Package Arch Version Repository Size
telnet i686 1:0.17-47.el6 base 56 k
telnet-server i686 1:0.17-47.el6 base 36 k
Installing for dependencies:
xinetd i686 2:2.3.14-33.el6 base 121 k
2.) Make sure that the xinetd service should be running.
# service xinetd status
xinetd (pid 13561) is running…
Please also note: Make sure that your firewall also stopped or the telnet traffic is allowed
3.) Configure the file name /etc/xinetd.d/telnet
We need to change the following highlighted line from yes to no
# vi /etc/xinetd.d/telnet
# default: on
# description: The telnet server serves telnet sessions; it uses \
# unencrypted username/password pairs for authentication.
flags = REUSE
socket_type = stream
wait = no
user = root
server = /usr/sbin/in.telnetd
log_on_failure += USERID disable = yes
In few scenarios, telnet works over the ip, but does not resolve specific ports. In that case xinetd services needs a restart
It can be said as a thin software layer on top of the hard drives and partitions, which creates illusion of continuity and easy of use for managing hard drives replacement, re-partitioning and backups.
It’s common usages are to manage large drives farm by adding a disk, replacing a disk, copy and share the disks without interrupting services running. For small setups there is no need to worry about partition size offering for requirements in future as disks partition can be re-sized easily on run-time, further making backups by taking snapshots and creating single logical volume of multiple physical volumes or entire hard disks functionality is also available.
Features of LVM
Re-size volume groups
Re-size logical volumes
Create read-only snapshot – LVM1
Create read-write snapshot – LVM2
Strips whole or parts of logical volumes (similar Raid0)
Mirror whole or parts of logical volumes (similar Raid1)
Move online logical volumes
Split or merge volume groups
Almost features can be performed online without disrupting users.
Some basic definition which I wanted to remember always, in my early stages, whereas which is very important to understand if someone will like to learn Unix / Linux with basic concepts rather then just a knowing.
Kernel – It is the core of the system. It controls all the tasks, schedules all the process and carries out all the functions of the operating system. It is the code that controls the interface between user programs and hardware devices. Please always remember it is not an operating system.
Shell – It is the command interpreter of the operating system. It accepts commands from the user and analyzes and interprets these commands. Hence shell acts as a middle man between the Kernel and the users of operating system.
Command – It is a instruction given by a user telling a computer to do something, such as to run a program.
Program – It is an executable file usually files that are stored in one of the bin directory.
Have figured out these definitions from numerous areas. Share more if you feel like to include in the list.
Path is an important area to understand when it comes to Unix / Linux.
What is PATH ?
It is an enviornmental variable in Unix / Linux that tells the shell which directories to search for executable files in response to commands issued by the user. Enviornmental variables are items for which values can be changed.
There are two types of PATH
1. Absolute Path
An abosolute path is easily recognized from the leading forward slash “/”. You start at the top level directory and continue down.
for e.g cd /boot/grub
2. Relative Path
A relative path doesn’t have a preceeding slash, usage of relative path is when you start from directory below the top level. This is dependent on where you are in the filesystem.
for e.g. While being in user’s home directory, going to /user/music you just type cd music
Note. My words are covered with my research therefore some might contain to some reference.
As I entered in the world of open-source by adopting Unix / Linux on my passion list, few basic things which I highlighted in the beginning were written down on a piece of paper. Thought to pool it down for my memories.
Unix / Linux
Minix – Unix like operating system before Linux
Unix – developed by Bill Labs
BSD – Popular distribution from University of California at Barkley
Main Purpose – Multitasking system for minicomputers
Linux originally developed by Linux Torvalds, began work in 1991 as a student in Finland at University of Helsinki
Linux Kernel – Lowest level core component is still maintained by Linus Torvalds
March 1994 – Version 1.0 finally was appeared.
Text Formatter (TeX) was by Donald Knutn
Linux is an inexpensive, efficient and robust system.
Hope you have got the vision of how basically we all started, like I have done. Share your experience for more fun.