Wednesday, October 15, 2014

Apache Server Interview Questions And Answers

Q:-Briefly explain Apache Web Server?
Answer: Apache Web Server is one of the most secure, powerful and popular open source HTTP Servers. It can be used to host anything from personal web sites to corporate domains.
Q: - What is location of log files for Apache server ?
Answer: /var/log/httpd

Q:-What is virtual hosting?
Answer: Virtual hosting is a method for hosting multiple domain names on a server using a single IP address. Virtual hosting allows one server to share its resources, such as memory and processor cycles, in order to use its resources more efficiently.

Q: - What are the types of virtual hosts ?
name-based and IP-based.
Name-based virtual host means that multiple names are running on each IP address.
IP-based virtual host means that a different IP address exists for each website served. Most configurations are named-based because it only requires one IP address.

Q: - How to restart Apache web server ?
Answer: service httpd restart
/etc/init.d/httpd  restart

Q: - How to check the version of Apache server ?
Answer: rpm -qa |grep httpd

Q: - What is meaning of "Listen" in httpd.conf file ?
Answer:Port number on which to listen for nonsecure (http) transfers.
Default port number of httpd is 80

Q: - What is DocumentRoot ?
Answer:it is a location of files which are accessible by clients. By default, the Apache HTTP server in RedHat Enterprise Linux is configured to serve files from the /var/www/html/ directory.

Q: - On which port Apache server works ?
Answer: http - port 80
               https - port 443

Q: - Tell me name of main configuration file of Apache server ?

Q: - What do you mean by a valid ServerName directive?
Answer:The DNS system is used to associate IP addresses with domain names. The value of ServerName is returned when the server generates a URL. If you are using a certain domain name, you must make sure that it is included in your DNS system and will be available to clients visiting your site.

Q: - What is the main difference between <Location> and <Directory> sections?
Answer:Directory sections refer to file system objects; Location sections refer to elements in the address bar of the Web page.

Q:-What is the difference between a restart and a graceful restart of a web server?
Answer:During a normal restart, the server is stopped and then started, causing some requests to be lost. A graceful restart allows Apache children to continue to serve their current requests until they can be replaced with children running the new configuration.
Q: - If you have added “loglevel Debug” in httpd.conf file, than what will happen?
 Answer: It will give you more information in the error log in order to debug a problem.

Q: - Can you record the MAC (hardware) address of clients that access your server?
Answer: No

Q: - Can you record all the cookies sent to your server by clients in Web Server logs?
Answer: Yes, add following lines in httpd.conf file.
CustomLog logs/cookies_in.log "%{UNIQUE_ID}e %{Cookie}i" CustomLog logs/cookies2_in.log "%{UNIQUE_ID}e %{Cookie2}i"

Q: - Can we do automatically roll over the Apache logs at specific times without having to shut down and restart the server?
Answer: Yes
Use CustomLog and the rotatelogs programs
Add following line in httpd.conf file. CustomLog "| /path/to/rotatelogs/path/to/logs/access_log.%Y-%m-%d 86400" combined

Q: - What we can do to find out how people are reaching your site?
Answer: Add the following effector to your activity log format. %{Referer}

Q: - If you have only one IP address, but you want to host two web sites on your server. What will you do?
Answer: In this case I will use Name Based Virtual hosting.
NameVirtualHost *:80
<VirtualHost *:80>
DocumentRoot /var/www/html/web1

<VirtualHost *:80>
DocumentRoot /var/www/html/web2

Q: - Can I serve content out of a directory other than the DocumentRootdirectory?
Answer: Yes, by using “Alias” we can do this.

Q: - If you have to more than one URL map to the same directory but you don't have multiple Alias directives. What you will do?
Answer: In this case I will use “AliasMatch” directives.
The AliasMatch directive allows you to use regular expressions to match arbitrary patterns in URLs and map anything matching the pattern to the desired URL.

Q: - How you will put a limit on uploads on your web server?
Answer: This can be achieved by LimitRequestBody directive.
<Directory "/var/www/html/data_uploads">
LimitRequestBody 100000
Here I have put limit of 100000 Bytes.

Q: - I want to stop people using my site by Proxy server. Is it possible?
Answer: <Directory proxy:>
Order Allow,Deny
Deny from all
Satisfy All

Q: - What is mod_evasive module?
Answer: mod_evasive is a third-party module that performs one simple task, and performs it very well. It detects when your site is receiving a Denial of Service (DoS) attack, and it prevents that attack from doing as much damage. mod_evasive detects when a single client is making multiple requests in a short period of time, and denies further requests from that client. The period for which the ban is in place can be very short, because it just gets renewed the next time a request is detected from that same host.

Q: - How t to enable PHP scripts on your server?
Answer: If you have mod_php installed, use AddHandler to map .php and .phtml files to the PHP handler. AddHandler application/x-httpd-php .phtml .php

Q: - Which tool you have used for Apache benchmarking?
Answer: ab (Apache bench)
ab -n 1000 -c 10

Q: - Can we cache files which are viewed frequently?
Answer: Yes we can do it by using mod_file_cache module.
CacheFile /www/htdocs/index.html.

Q:- How do you check for the httpd.conf consistency and any errors in it?
Answer: httpd –t

Q:- Apache runs as which user? and location of main config file?.
Answer:  Apache runs with the user “nobody” and httpd daemon. Apache main configuration file: /etc/httpd/conf/httpd.conf (CentOS/RHEL/Fedora) and /etc/apache2.conf (Ubuntu/Debian).

Q:- On which port Apache listens http and https both?
Answer : By default Apache runs on http port 80 and https port 443 (for SSL certificate). You can also use netstat command to check ports.

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