Linux Administration for Developersby

Mahmoud Said

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Outline

● Why

● Linux Basics

● Servers

● WTF

● More monitoring tools

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Why

● Free

● Hosting Open Source web apps

● Developing Open Source apps

● Robustness

● Development by Community

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Why

Admin DeveloperCommonKnowledge

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Linux Basics

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Filesystem

“Everything is a file” ● Regular files

● Directories

● Symbolic links

● Hard links

● Devices

● Sockets

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Filesystem - Filenames

● Case sensitive

● Can contain any character except “/”

● Extensions are only used for user convenience

● Examples:README .bashrc index.htmlMy World conf.old database.yml.bak

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Filesystem – File pathes

● Sequence with nested directories ending with or without a file

● Relative: config/database.yml

● Absolute: /etc/nginx/nginx.conf

● Special pathes: ~/ #home of current user/ # root.. # parent directory

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Shells

● Interface to execute user commands

● Hide the details of the OS

● Text based Commands

● Can be scripted

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Famous Shells

● sh The Bourne shell (obsolete)Traditional, basic shell found on Unix systems, by Steve Bourne.

● csh The C shell (obsolete)Once popular shell with a C-like syntax

● bash The Bourne Again shell (most popular)An improved implementation of sh with lots of added features.

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Scripting

● Commands to the shell can be scripted

● The script can be passed to the interpreter, or it can be executed by specifying the interpreter at the beginning

#!/bin/bashecho “bash script...”

#!/usr/bin/rubyputs “ruby script...”

bash init.sh.old./init.sh.old

ruby setup.rb./setup.rb

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Common bash commands

pwdls cp cd man

catlessmorevimnano

findsortwcaliasecho

lnchmodchown

tailheadgrepcrontab

mkdir mv rmrmdir

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Bash Keyboard commands

● TAB # auto completion

● CTRL+R # search commands history

● CTRL+D # exit the current shell

● CTRL+P # previous command (also “up”)

● CTRL+N # next command (also “down”)

● CTRL+L # clear screen

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Standard I/O & piping

● Redirect output to a file using “>”

● Append output to a file using “>>”

● Obrain input from a file using “<”

● Redirect output as input to another process (piping) “|”

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Servers

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ssh access

● Using password

● Public/private key pair

ssh user@35.231.23.120 -p5022 ( default 22)

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Important paths

/usr/local/project Root directory (capistrano convension)

/var/log/ all important logs

/etc/ system configuration files

/etc/init.d/ startup scripts

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Uploading/Downloading files

● scp scr_file user@server.com:/dst_path/

● wget http://www.akhbarak.net/traces.log.gz

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Server Anatomy

Web server

Application server

Database

Memcache

Indexer

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WTF!!

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WTF

● Something wrong

● Too few details

● Admin/dev related

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Identifying the problem

● Browser/Firebug

● Isolating the request

● Logs

– Application logs

– Web server logs

– Other logs

● Rails console

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System status

● System load/CPU (top)

● IO (iotop)

● Memory (free -m, top)

● Check processes (ps aux | grep ruby)

● ….

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Monitoring Tools

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Newrelic.com

● Multiple technologies

● Performance analysis

● Server monitoring

● Traces of errors & slow requests

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Thank You