Devops for beginners

Server
Server, it is just a machine(host/guest vm) which is configured with some services or running
instances of an application (software) capable of accepting requests from the client and giving
responses accordingly.
We use Linux servers
Linux is a kernel, on which basis there are number of OS flavours are avaiilable
● Ubuntu
● RedHat
● CentOS
● Debian & etc
Principle of linux
1. Everything is a file :
2. Configuration data of the system is stored in text usually named with extension, .conf
3. Connection pipes for standard I/O to chain programs

1. /etc/group File – Group Information:
Holds 4 information delimited by colon(:) in the following format.
group_name:x:group_id:users
2. /etc/passwd File – User Information:
It holds 7 information delimited by colon(:).
user_login:x:user_id:user_primary_group_id:comment_or_user_name:home_directory_path:default_login_shell
3. /etc/shadow File – User Login Information:
• User name : It is your login name.
• Password: It your encrypted password. The password should be minimum 6-8 characters long including special characters/digits
• Last password change (lastchanged): Days since Jan 1, 1970 that password was last changed.
• Minimum: The minimum number of days required between password changes i.e. the number of days left before the user is
allowed to change his/her password.
• Maximum: The maximum number of days the password is valid (after that user is forced to change his/her password).
• Warn : The number of days before password is to expire that user is warned that his/her password must be changed.
• Inactive : The number of days after password expires that account is disabled.
• Expire : days since Jan 1, 1970 that account is disabled i.e. an absolute date specifying when the login may no longer be used.
● A system user is intended to be used by programs (applications).
● A normal user is intended to be used by people (like you and me).

Syntax:# useradd options user_name
Syntax:# useradd -D
Syntax :# useradd -u 106 -g 508 -c “This is a linux group” -d /home/vivek -s /bin/bash vivek
Syntax:# usermod -s /bin/sh vivek
Syntax:# userdel vivek
Command Group-Id Home Directory
ShellCommentUser_id
UserName

Syntax:# groupadd options group_name
-F : If the group is already available then it should display.
-g : Group ID is supplied by this actions.
-o : giving ID which is not unique
-r : Add to system account.
Syntax:# groupdelete group_name
Syntax:# passwd
Output:
Changing password for test.
(current) UNIX password:
Enter new UNIX password:
Retype new UNIX password:
passwd: password updated successfully

Syntax:# pwd
Syntax:# cd
Syntax:# ls options arguments
Command Result
ls List the files in the working directory
ls /bin List the files in the /bin directory (or any other directory you care
to specify)
ls -l List the files in the working directory in long format
ls -l /etc
/bin
List the files in the /bin directory and the /etc directory in long
format
ls -la .. List all files (even ones with names beginning with a period character,
which are normally hidden) in the parent of the working directory in
long format
O/P $ pwd
/Users/vivek
viveks-MacBook-Pro:~ vivek$ cd /usr/X11R6
viveks-MacBook-Pro:X11R6 vivek$ pwd
/usr/X11R6
The "." symbol refers to the working
directory and the ".." symbol refers to
the working directory's parent directory.

viveks-MacBook-Pro:~ vivek$ ls -la
-rw------- 1 root wheel 576 Apr 17 1998 vivek.txt
drwxr-xr-x 6 root wheel 1024 Oct 9 1999 Projects
-rw-rw-r-- 1 root wheel 276480 Feb 11 20:41 vivek.sql
-rw------- 1 root wheel 5743 Dec 16 1998 .Xauthority
---------- ------- ------- -------- ------------ -------------
| | | | | |
| | | | | File Name
| | | | |
| | | | +--- Modification Time
| | | |
| | | +------------- Size (in bytes)
| | |
| | +----------------------- Group
| |
| +-------------------------------- Owner
|
+---------------------------------------------- File Permissions
Syntax:# less file_name

Syntax:# find path pattern
Syntax:# find . -name foo
Syntax:# locate pattern
Syntax:# locate finger
Syntax:# which command
Syntax:# which gedit
/usr/bin/gedit
Syntax:# whereis command
Syntax:# whereis find
/usr/bin/find /usr/share/man/man1p/find.1p.gz /usr/share/man/man1/find.1.gz
The above command searches through the current
working directory for all files with "foo" in
their name.
The search results could include a file called finger.
txt, a file called pointerfinger.txt, a directory named
/fingerthumbnails/, and so on. To learn more about
locate, read the locate man page.
which returns the location of binary, or executable,
shell commands. The information provided by which is
useful for creating application launchers.
The following command returns the locations of: the
binary of find, the location of the source code, and the
location of the find man page.

Syntax:# cp [options] source dest
Syntax:# mv [options] source destination
viveks:~ vivek$ cp -u *.html /test
only copy all the HTML files that did not
exist in the test directory or were newer
than the versions in the destination
directory

Syntax:# rm [options] file_name/directory_name
Syntax:# mkdir diectory
Syntax:# touch [options] file_name

Syntax:# cat [options] file_name
Syntax:# cat > file_name
Syntax:# cat >> file_name
Syntax:# cat -n file_name
Syntax:# sort filename
$ ls -lt | sort -n -k 5
-rw-r--r-- 1 vivek vivek 0 2012-12-03 00:09 1sampleFile.txt
total 44
-rw-r--r-- 1 vivek vivek 6 2012-12-03 01:03 file
-rw-r--r-- 1 vivek vivek 6 2012-12-03 01:04 file2
-rw-r--r-- 1 vivek vivek 6 2012-12-03 01:10 sfile
-rw-r--r-- 1 vivek rupali 15 2012-12-03 01:12 strfile2
-rw-r--r-- 1 vivek vivek 21 2012-12-03 01:13 strfile

Syntax:# wc [options] file_name
wc -l : Prints the number of lines in a file.
wc -w : prints the number of words in a file.
wc -c : Displays the count of bytes in a file.
wc -m : prints the count of characters from a file.
wc -L : prints only the length of the longest line in a file.

viveks:~ vivek$ ls -l /bin/bash
-rwxr-xr-x 1 root root 316848 Feb 27 2013 /bin/bash
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Syntax:# chmod 600 some_file
Syntax:# su

Syntax:# chown [OPTION] [OWNER][:[GROUP]] FILE
Syntax:# chown -r vivek:staff /home/vivek/projects

Syntax:# ps
PID PPID PGID TTY UID STIME COMMAND
2152 1 2152 con 1000 13:19:07 /usr/bin/bash
2276 2152 2276 con 1000 14:53:48 /usr/bin/ps

$ ./analyze results*.dat
...a few minutes pass...
^C
$ ./analyze results*.dat &
[1] 6891
$ jobs
[1] ./analyze results01.dat results02.dat results03.dat
$ fg
Show background processes
Bring background job to foreground
Use fg %1, fg %2, etc. if there are
several background jobs

$ ./analyze results01.dat
^Z
[1] Stopped ./analyze results01.dat
$ bg %1
$ sleep 120; echo “I am awake.”

$ kill %1
[1]+ Terminated ./analyze results01.dat
$ kill pid
$ killall ./analyze
$ killall -9 ./analyze
$ nohup ./analyze results01.dat &

MyFile
Syntax:# ls > MyFile.txt
Syntax:# sort > MyFile.txt

Syntax:# command 1>output_file 2>error_file
Syntax:#
Syntax:# Syntax:# command >&output_file
Syntax:# ls -lR >everything 2>/dev/null

Syntax:# cat MyFile.txt | sort | lpr
P
I
P
E
P
I
P
E
>
<
>>
2>
Redirect the output of a command,
input to a command, or diagnostic
output into some file or I/O
device.
|
Redirect the output of a command to
become the input to another
command.

Program What it does
sort Sorts standard input then outputs the sorted result on standard output.
uniq Given a sorted stream of data from standard input, it removes duplicate lines
of data (i.e., it makes sure that every line is unique).
grep Examines each line of data it receives from standard input and outputs every
line that contains a specified pattern of characters.
head Outputs the first few lines of its input. Useful for getting the header of a
file.
tail Outputs the last few lines of its input. Useful for things like getting the
most recent entries from a log file.
sed Stream editor. Can perform more sophisticated text translations than tr.
awk An entire programming language designed for constructing filters. Extremely
powerful.

Compressing/Uncompress file or directories
tar
gzip
zip
Copy/Transfer file or directory to remote server
rsync
scp

Syntax:# bzip2 MyFile.txt
Syntax:# bunzip2 MyFile.txt.bz2
Compression Tool File Extension Decompression Tool
bzip2 .bz2 bunzip2
gzip .gz gunzip
zip .zip unzip

Syntax:# gzip MyFile.txt
Syntax:# gunzip MyFile.txt.gz
Syntax:# gzip -r MyFile.gz file1 file2 file3 /home/vivek/work
Syntax:# zip MyFile.txt
Syntax:# gunzip MyFile.txt.zip

●
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●
●
●
●
Syntax:# tar -cvf filename.tar directory/file
Syntax:# tar -tvf filename.tar directory/file
Syntax:# tar -tvf filename.tar directory/file
Syntax:# tar -czvf filename.tgz file

Compressing Files
Syntax Description Example(s)
gzip
{filename}
Gzip compress the size of the given files using
Lempel-Ziv coding (LZ77). Whenever possible, each file
is replaced by one with the extension .gz.
gzip mydata.doc
gzip *.jpg
ls -l
bzip2
{filename}
bzip2 compresses files using the Burrows-Wheeler block
sorting text compression algorithm, and Huffman
coding. Compression is generally considerably better
than that achieved by bzip command (LZ77/LZ78-based
compressors). Whenever possible, each file is replaced
by one with the extension .bz2.
bzip2 mydata.doc
bzip2 *.jpg
ls -l
zip {.zip-
filename}
{filename-to-
compress}
zip is a compression and file packaging utility for
Unix/Linux. Each file is stored in single .zip {.zip-
filename} file with the extension .zip.
zip mydata.zip
mydata.doc
zip data.zip *.
doc
ls -l
tar -zcvf {.
tgz-file}
{files}
tar -jcvf {.
tbz2-file}
{files}
The GNU tar is archiving utility but it can be use to
compressing large file(s). GNU tar supports both
archive compressing through gzip and bzip2. If you
have more than 2 files then it is recommended to use
tar instead of gzip or bzip2.
-z: use gzip compress
-j: use bzip2 compress
tar -zcvf data.
tgz *.doc
tar -zcvf pics.
tar.gz *.jpg *.
png
tar -jcvf data.
tbz2 *.doc
ls -l

gzip -l {.gz file} List files from a GZIP archive gzip -l mydata.doc.gz
unzip -l {.zip file} List files from a ZIP archive unzip -l mydata.zip
tar -ztvf {.tar.gz}
tar -jtvf {.tbz2}
List files from a TAR archive tar -ztvf pics.tar.gz
tar -jtvf data.tbz2
gzip -d {.gz file}
gunzip {.gz file}
Decompressed a file that is created
using gzip command. File is restored
to their original form using this
command.
gzip -d mydata.doc.gz
gunzip mydata.doc.gz
bzip2 -d {.bz2-file}
bunzip2 {.bz2-file}
Decompressed a file that is created
using bzip2 command. File is restored
to their original form using this
command.
bzip2 -d mydata.doc.bz2
gunzip mydata.doc.bz2
unzip {.zip file} Extract compressed files in a ZIP
archive.
unzip file.zip
unzip data.zip resume.doc
tar -zxvf {.tgz-file}
tar -jxvf {.tbz2-file}
Untar or decompressed a file(s) that
is created using tar compressing
through gzip and bzip2 filter
tar -zxvf data.tgz
tar -zxvf pics.tar.gz *.jpg
tar -jxvf data.tbz2

Syntax:# vmstat 3
Display Memory Utilization Slabinfo
Syntax:# vmstat -m
Get Information About Active / Inactive Memory Pages
Syntax:# vmstat -a
Syntax:# w user_name
Syntax:# w vivek
Syntax:# uptime
18:02:41 up 41 days, 23:42, 1 user, load average: 0.00, 0.00, 0.00
Syntax:# uptime

Webserver
A web server is a computer system that processes requests via HTTP,
In sinpme word - The basic network protocol used to distribute information on the World Wide Web.
We use - Apache & Nginx
Apache
The Apache HTTP Server Project is an effort to develop and maintain an open-source HTTP server
for modern operating systems including UNIX and Windows NT
Rails App - Load Passenger
PHP App - Load PHP module
Python APP - Load PYthon FCGI Module
Nginx
Nginx (pronounced engine-x) is a free, open-source, high-performance HTTP server and reverse
proxy, Nginx dosen’t include any module to interpret server side script. Always need to configure a
service to interpret server side scripting.
Rails App - Unicorn, passenger
PHP App - PHP-FPM, PHP-FastCGI
Python App - WSCGI

Sample Vhost Configuration
<VirtualHost *:80>
DocumentRoot
/var/www/example1
ServerName www.example.
com
# Other directives here
</VirtualHost>
server {
listen 80;
server_name www.example.com;
root /var/www/example.com;
index index.html index.htm;
# Other directives here
}

Server Security
Its a terminology which defines the machine connected to internet & stands to server some kind of
request that should be secured. Securing server also knowns as a server hardening
In a simple word
● No access to unauthorized user
● Secure from hacker attacks
● Apply security & PCI compliance policies
● Secure app from sql injection attacks
● Use secure protocol if sending confidential data over the network
● Apply firewall rules.
In basic practices, follow the below mentioned rules in given manner.
Firewall rules(iptables in linux), UFW, Fail2ban
Selinux (If exist)
Secure server at service level
Special permissions (ACL)
Simple permission/ User level permissions

Log Management
Log management (LM) comprises an approach to dealing with large volumes of computer generated
log messages. To ensure rotate unwanted logs file to avoid unwanted disk space consumption.
There are two approaches for log management
Rotate logs on the local system(on the same machine)
rsync the computer generated log to some other location/Server.
Some time these issues create critical situations like crashing servers, service not able to generate
files, no disk space left but inode is free etc.
Linux provides a service called logrotate. which helps to manage logs on local system. And rsyslog
to transfer logs to remote server
In our practices
Rotates the log file(App log, service logs, system logs etc) according to size, weekly rotation,
daily rotation.
Purging old log files which are no more needed.

Installing software on Linux involves package managers and software repositories or install from
source code.
Different flavour of linux based OS have its own package manager.
Debian,Ubuntu - apt-get or dpkg
Fedora, CentOS - yum, rpm
Opensuse - Zypper
To list installed packages -:
dpkg -l (ubuntu),
rpm -qa (centOS)
To install package -:
apt-get install <packagename>(ubuntu),
yum install <packagename>(CentOS)
To remove packages -:
apt-get remove/purge <packagename>(ubuntu),
yum remove/purge <packagename>(CentOS)

Virtualization
Virtualization, in computing, refers to the act of creating a virtual (rather than actual) version of
something, including but not limited to a virtual computer hardware platform, operating system (OS),
storage device, or computer network resources.
Type of virtualization -:
Full-VirtualizaTion
Almost complete simulation of the actual hardware to allow software, which typically consists of
a guest operating system, to run unmodified.
Para-virtualization
A hardware environment is not simulated; however, the guest programs are executed in
their
own isolated domains, as if they are running on a separate system. Guest programs need to be
specifically modified to run in this environment.

Cloud
The practice of using a network of remote servers hosted on the Internet to store, manage, and
process data, rather than a local server or a personal computer.
Cloud computing is computing in which large groups of remote servers are networked to allow the
centralized data storage, and online access to computer services or resources. Clouds can be
classified as public, private or hybrid.
Public Cloud - A cloud is called a "public cloud" when the services are rendered over a network that
is open for public use. Public cloud services may be free or offered on a pay-per-usage model.
Private Cloud - Private cloud is cloud infrastructure operated solely for a single organization, whether
managed internally or by a third-party, and hosted either internally or externally.
Hybrid CLoud - Hybrid cloud is a composition of two or more clouds (private, community or public)
that remain distinct entities but are bound together

Cloud Server
A cloud server is a logical server that is built, hosted and delivered through a cloud computing
platform over the Internet. Cloud servers possess and exhibit similar capabilities and functionality to a
typical server but are accessed remotely from a cloud service provider.
Most used ones are -:
AWS(Amazon Web Service)
Rackspace cloud
sometime other cloud provider
AWS S3 service
Amazon S3 (Simple Storage Service) is an online file storage web service offered by
Amazon Web Services. Amazon S3 provides storage through web services interfaces (REST, SOAP,
and BitTorrent).
Block storage
Extra block storage which can we create on-demand and attach it to the server instance
for additional state.
Snapshot
This is just clone of the server attached block storage, which is taken as a backup. From this
snapshot we can create new ebs from that.

Configuration management is a techniques to manage server/nodes from a central
location/workstation. By which you can manage users, groups, packages & deployments rather than
the files that manage those on each type of server you have.
Configuration management also store everything in a central place, which allows admins to quickly
verify or change services across the network, automate their monitoring infrastructure, and gather data
about the state and status of their network
I prefer to use chef
Chef turns infrastructure into code. With Chef, you can automate how you build, deploy,
and manage your infrastructure. From 6 months back, we are using chef to setup server infra.
Using for
Server setup
Enabling Monitoring
Enabling security
Setup backups

Sharing static data between servers
Synchronize static data & data storage across the pool of real servers. Which is used by
the application to store data like images, audio etc.
Most use protocol is -:
NFS server - The protocol which enabled file sharing between servers.
S3 - AWS simple storage service which allow us to store data on cloud using REST, s3cmd etc
.

Devops for beginners

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