Unix Interview Questions and Answers for experienced

Question: What are filters?
Its a program which filter the data before execute on application OR database.

Question: What is Syntax for commands?

Command [-argument] [-argument] [–argument] [file]

Question: How to delete all the fies from current directory?

rm –r *

Question: What is Kernel?
Kernel is the UNIX operating system. It is the master program that controls the resources and allotting them tasks.


Question: What is Shell?
A shell acts as an interface between the user and the system.


Question: What are some common shells and what are their indicators?
sh – Bourne shell
csh – C SHell
bash – Bourne Again Shell
tcsh – enhanced C Shell
zsh – Z SHell
ksh – Korn SHell



Question: What is inode?
The inode is a data structure in a file system. Each inode stores the attributes and disk block location(s) of the object's data.


Question: What is Swapping?
The whole process in swapping is moved from the swap device to the main memory for execution. The process size must be less than or equal to the available main memory.


Question: What is Paging?
In this, only required memory pages are moved to main memory for execution.


Question: What is ephemeral port in UNIX?
Ephemeral ports are used by Operating system for client sockets.


Question: What is Bash Shell?
t is a free shell designed to work on the UNIX system. Being the default shell for most UNIX-based systems, it combines features that are available both in the C and Korn Shell.


Question: What is piping?
Piping, represented by the pipe character "|" and used to combine two or more commands together.
For Example:

uhunix% ls | grep username

Question: How to set the path in UNIX?

set path = [directory path]

Question: How do you find how many cpu are in your system and there details?

cat /proc/cpuinfo

Question: How do you find for how many days your Server is up?

uptime 

Question: How do you find whether your system is 32 bit or 64 bit?

arch

Question: What is tee command?
It is used to
a) get data from the standard input. b) send it to standard output.


Question: What is pid?
Pid is short for Process ID
. It is used to identify every process that runs on the UNIX system.



Question: What command will change your prompt to MYPROMPT?

PS1 = "MYPROMPT:"

Question: Write command to list all the links from a directory

ls -lrt | grep "^l"

Question: How to reboot all services in linux

reboot

Question: How to check http serverice

service httpd status

Question: How to stop http

service httpd stop

Question: How to start http

service httpd start

Question: How to check MysQL service

service mysqld status

Question: How to stop mysql

service mysqld stop

Question: How to start mysql

service mysqld start

Question: How to start nodeJS

node fileName.js

Question: How to start nodeJS permanently

nohup node server.js &
rm nohup.out

Redis PHP Interview questions and answers

Question: What is Redis?
Redis is an advanced key-value data store and cache. It has is also referred to as a data structure server as such the keys not only contains strings, but also hashes, sets, lists.


Question: What are the advantages of using Redis?

1. It provides high speed
2. It has got command level Atomic Operation (tx operation)
3. It supports a server-side locking
4. It has got lots of client lib

Question: What are the limitations of Redis?

1. It is single threaded
2. It has got limited client support
3. It is not deployed

Question: Why Redis is different as compared to other key-value stores?

1. Redis values can contain more complex data types, with atomic operations.
2. Redis is an in-memory but persistent on disk database.

Question: How to delete current database?

redis-cli flushdb

Question: How to remove all database?

redis-cli flushall

Question: How to check redis is running?

try {
    $redis = new Redis();
    $redis->connect('127.0.0.1', 6379);
    echo "Redis is running.";
    echo "Server is running: " . $redis->ping();
} catch (Exception $e) {
    echo $e->getMessage();
}

Question: How to set value in redis?

$redis->set("name", "Set string in redis");

Question: How to get value from redis?

 echo $redis->get('name'); //Set string in redis

Question: How to set multiple values (Array) in redis?

$redis->lpush("tutorials", "PHP");
$redis->lpush("tutorials", "MySQL");
$redis->lpush("tutorials", "Redis");
$redis->lpush("tutorials", "Mongodb");
$redis->lpush("tutorials", "Mysql");

Question: How to get array data from redis?

$list = $redis->lrange("tutorials", 0 ,5);   
print_r($list);
/*Array ( [0] => Mysql [1] => Mongodb [2] => Redis [3] => MySQL [4] => PHP [5] => Mysql ) */

Question: How to get all keys from redis?

$keyList = $redis->keys("*");
print_r($keyList);
/*Array ( [0] => tutorials [1] => name ) */

Question: How to stop redis?

/etc/init.d/redis-server stop

Question: How to start redis?

/etc/init.d/redis-server start

Question: How to re-start redis?

/etc/init.d/redis-server restart

Question: How do I move a redis database from one server to another?

1. use BGSAVE command to Save a spanshot of the database into a dump.rdb
2. Copy this dump.rdb file into another server.

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