Some linux background needed for web and rails developers. Internal session for interns and new comers at eSpace

1. IT Operations for Web Developers
Mahmoud Said aka @modsaid

2. Outline
● Why This Session?
● The Shell
● Basics
● ssh & authenticating
● Server Anatomy
● Nginx, passenger
● Webistrano
● File transfer
● Troubleshooting (metrics, logs)
● Behind Closed Doors

3. Why?
Administration
(IT Operations)
Development
Team
Common
knowledge

4. DevOps
“DevOps is a software development method that stresses communication, collaboration
and integration between software developers and information technology (IT)
professionals.” Wikipedia

5. The Shell
● Hides hardware and OS details
● Text based Command Line interface
● Sequence of commands are “scripts”

6. The Shell
● There is no recycle bin, and no undo.. “Read
before you hit Enter”
Realizing a wrong chown -R (http://devopsreactions.tumblr.com/)

7. The basics
● Everything is a file
● Files names are case sensitive and do not
contain '/'
● Extensions are just conventions

8. ssh and Authentication
● Command line based sessions on the server
● apt-get install openssh-client
● Authentication via password or key pair
.ssh/id_rsa (and .ssh/id_rsa.pub)
.ssh/known_hosts
● Server
.ssh/authorized_keys

9. ssh bookmarking
.ssh/config Host myserver
Hostname myserver.com
User myuser
Port 3022
Host ldap
Hostname 66.85.165.135
User mahmoud

10. Connecting through ssh
ssh myuser@myserver.com -p3022
ssh myserver

11. Server Anatomy
Web Server (nginx, apache)
Application Server
(Passenger, thin, mod_php, tomcat,..)Other Services
Memcache
Solr
DB Server
Processes
(background jobs)
File system
(Static Resources)

12. nginx
● High-performance HTTP server and reverse
proxy
● /etc/nginx/sites-enabled/kelmetak.com
server {
listen 80 default;
server_name kelmetak.com 2ad.kelemtak.com;
root /usr/local/politwoops/current/public;
}

13. Passenger
● Rails (and rack) nginx and apache module (like
mod_php for php)
server {
listen 80;
server_name 2ad.kelmetak.com;
root /usr/local/politwoops/current/public;
passenger_enabled on;
}

14. More on nginx
● Response cache headers
● Memcache directly
● Rewrites
● Constraints
● Load balancing
● proxy-pass
server {
listen 80;
server_name app.com;
location ~ ^/(assets)/ {
gzip_static on;
expires max;
add_header Cache-Control public;
}
}

15. webistrano
● Easy automated deployments
● Based on capistrano
● Let's dive together

16. File transfer
● Scp
● Rsync
● wget

17. WTF !!

18. Troubleshooting
● Troubleshooting
● Metrics
– CPU, Memory, I/O
● Tools
– top, htop, free -m, ps, iotop, iftop

19. Troubleshooting (2)
● Logs
– /var/log/nginx/access.log
– /var/log/nginx/error.log
– /usr/local/myproject/current/log/production.log
– Custom logs

20. Troubleshooting (3)
● Newrelic is your friend
● Debugging via rails console
● Debugging via separate “rails server”

21. Behind Closed doors

22. Firewall
● Allow/deny connections based on
– Source/destination ip
– Port
– Protocol
● Everything should be closed, open only what's
needed

23. ssh tunneling
● A way to access closed ports through your ssh
connection
ssh myserver -L port:host:hostport
ssh myserver -L 3056:localhost:3055

24. Open Discussion

25. Thank You
Mahmoud said
mahmoud.said@espace.com.eg
@modsaid