1)Give me 15 commands which you use frequently

Depends on the environment you work. Some examples are

mkdir — For creating folders( use -p option to create multiple folders at a time)
ls –List folders/files( check what ls -1 do)

top — To monitor system activities

lsof –To check whats happening on the server and which process open which file.

netstat -tcp –Gives you complete picture about network connection details.

vnstat –Gives you Network band width statics

sh –For running shell scripts

history –For monitoring the commands executed by users

cd –For changing directories

vi --For editing configuration files.

chmod –To change permissions of folders and files.

mount –For mounting formated partitions.

service –For start/restart/stop a service.

chkconfig –For permanent on/off a service.

fdisk -l –To list all the partitions

This is my own list, you can have your list.

2)Give me some commands for user management.

last, chage, chsh, lsof, chown, chmod, useradd, userdel, newusers.

3)Give me syntax checking commands for following services

DNS, SAMBA, Apache etc

4)What is the command to do password less logins to other machines.

expect and ssh-keygen

5)Give me some security monitoring related commands.

lsof, netstat, top, ps -ef, tail, last, tcpdump, sestatus, history, w.

6)What is the difference between man, info, whatis commands and a –help option for a command?

whatis gives you one line answer.

–help option for a command gives you one line answers for each option supported by a command

man command gives you medium size info.

info command gives full details about a commands, lots and lots of information about a command.

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