Wednesday, August 21, 2013

Installing on centos 6.4 (64-bit)

NOTES: epel has another package called docker (which is a KDE docking application and is not related to this). So, you will get an error performing these steps, if you have that package already installed.

UPDATE-1: Docker version-0.6.1 is released. Upgrade instructions are available here

UPDATE-2: Docker version-0.6.2 is released. is the lightweight "container engine + image repository" built on top of LXC (linux lightweight containers) to ship any application.

At the core of there are
  1.  an application "/usr/bin/docker" 
  2.  set of pre-created operating-system/application images hosted with ""
  3.  AUFS (Another Union filesystem) to take care of snapshots, diffs, ro/rw requirements
  4. LXC (Linux lightweight containers)
  5. cgroups (for resource management and namespacing)
As of writing this blog, the latest version is 0.5.3 . The project is actively being developed and things can change in near future.

Follow these instructions to get installed on your system.

0. Install centos 6.x

1. Disable selinux as it interferes with functionality of LXC

[root@localhost ~]# cat /etc/selinux/config 
# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
#       enforcing - SELinux security policy is enforced.
#       permissive - SELinux prints warnings instead of enforcing.
#       disabled - SELinux is fully disabled.
# SELINUXTYPE= type of policy in use. Possible values are:
#       targeted - Only targeted network daemons are protected.
#       strict - Full SELinux protection.
2. Download and setup Fedora EPEL Repository

sudo yum install

3. Setup repository

cd /etc/yum.repos.d
sudo wget

4. Install docker-io package

[root@localhost ~]# yum install docker-io
Loaded plugins: fastestmirror, security
Loading mirror speeds from cached hostfile
 * base:
 * epel:
 * extras:
 * updates:
Setting up Install Process
Resolving Dependencies
--> Running transaction check
---> Package docker-io.x86_64 0:0.5.3-4.el6 will be installed
--> Processing Dependency: lxc >= 0.8.0 for package: docker-io-0.5.3-4.el6.x86_64
--> Processing Dependency: kernel-ml-aufs >= 3.10.5 for package: docker-io-0.5.3-4.el6.x86_64
--> Running transaction check
---> Package kernel-ml-aufs.x86_64 0:3.10.5-3.el6 will be installed
---> Package lxc.x86_64 0:0.8.0-3.el6 will be installed
--> Processing Dependency: for package: lxc-0.8.0-3.el6.x86_64
--> Running transaction check
---> Package lxc-libs.x86_64 0:0.8.0-3.el6 will be installed
--> Finished Dependency Resolution

Dependencies Resolved

 Package                   Arch              Version                  Repository       Size
 docker-io                 x86_64            0.5.3-4.el6              hop5            1.2 M
Installing for dependencies:
 kernel-ml-aufs            x86_64            3.10.5-3.el6             hop5             33 M
 lxc                       x86_64            0.8.0-3.el6              hop5             81 k
 lxc-libs                  x86_64            0.8.0-3.el6              hop5             75 k

Transaction Summary
Install       4 Package(s)

Total download size: 34 M
Installed size: 159 M
Is this ok [y/N]: y
Downloading Packages:
(1/4): docker-io-0.5.3-4.el6.x86_64.rpm                              | 1.2 MB     00:03     
(2/4): kernel-ml-aufs-3.10.5-3.el6.x86_64.rpm                        |  33 MB     00:33     
(3/4): lxc-0.8.0-3.el6.x86_64.rpm                                    |  81 kB     00:00     
(4/4): lxc-libs-0.8.0-3.el6.x86_64.rpm                               |  75 kB     00:00     
Total                                                       896 kB/s |  34 MB     00:39     
Running rpm_check_debug
Running Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing : lxc-libs-0.8.0-3.el6.x86_64                                              1/4 
  Installing : lxc-0.8.0-3.el6.x86_64                                                   2/4 
  Installing : kernel-ml-aufs-3.10.5-3.el6.x86_64                                       3/4 
  Installing : docker-io-0.5.3-4.el6.x86_64                                             4/4 
  Verifying  : kernel-ml-aufs-3.10.5-3.el6.x86_64                                       1/4 
  Verifying  : lxc-0.8.0-3.el6.x86_64                                                   2/4 
  Verifying  : lxc-libs-0.8.0-3.el6.x86_64                                              3/4 
  Verifying  : docker-io-0.5.3-4.el6.x86_64                                             4/4 

  docker-io.x86_64 0:0.5.3-4.el6                                                            

Dependency Installed:
  kernel-ml-aufs.x86_64 0:3.10.5-3.el6               lxc.x86_64 0:0.8.0-3.el6              
  lxc-libs.x86_64 0:0.8.0-3.el6                     

[root@localhost ~]#

5. See the package is installed correctly

[root@localhost ~]# docker -h
Usage of docker:
  -D=false: Debug mode
  -H=[unix:///var/run/docker.sock]: tcp://host:port to bind/connect to or unix://path/to/socket to use
  -api-enable-cors=false: Enable CORS requests in the remote api.
  -b="": Attach containers to a pre-existing network bridge. Use 'none' to disable container networking
  -d=false: Daemon mode
  -dns="": Set custom dns servers
  -g="/var/lib/docker": Path to graph storage base dir.
  -p="/var/run/": File containing process PID
  -r=false: Restart previously running containers

6. Add cgroup filesystem to /etc/fstab , so that docker will work correctly

[root@localhost ~]# echo "none                    /sys/fs/cgroup          cgroup  defaults        0 0" >> /etc/fstab 
[root@localhost ~]# mount /sys/fs/cgroup

Per "Peter Zimmerman" a reboot is needed to actually mount /sys/fs/cgroup (due to the kernel doesn't have cgroup support). So, the above mount step is not really needed. As its used only upon reboot.

7. Reboot the system ; make sure to select "3.10.5-3.el6.x86_64" kernel version while booting.

8. Once system is up and running, make sure you are on right kernel

[root@localhost ~]# uname -r

[root@localhost ~]# grep aufs /proc/filesystems 
nodev   aufs
9. Start the in daemon mode (in a different terminal)

[root@localhost ~]# docker -d 
2013/08/21 07:47:07 WARNING: Your kernel does not support cgroup swap limit.
2013/08/21 07:47:07 Listening for HTTP on /var/run/docker.sock (unix)

10. Print hello world from a centos 6.4 container.

[root@localhost ~]# docker run centos:6.4 echo "hello world"
2013/08/21 07:48:41 POST /v1.4/containers/create
2013/08/21 07:48:41 POST /v1.4/containers/c6bc9e80097e/start
2013/08/21 07:48:41 POST /v1.4/containers/c6bc9e80097e/attach?logs=1&stderr=1&stdout=1&stream=1
hello world

11. Ping from inside the container
[root@localhost ~]# docker -dns '' run centos:6.4 ping -c 3
2013/08/21 08:02:15 POST /v1.4/containers/create
2013/08/21 08:02:15 POST /v1.4/containers/c40a1244f9bc/start
2013/08/21 08:02:15 POST /v1.4/containers/c40a1244f9bc/attach?logs=1&stderr=1&stdout=1&stream=1
PING ( 56(84) bytes of data.
64 bytes from ( icmp_seq=1 ttl=48 time=323 ms
64 bytes from ( icmp_seq=2 ttl=48 time=329 ms
64 bytes from ( icmp_seq=3 ttl=49 time=302 ms

--- ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2304ms
rtt min/avg/max/mdev = 302.032/318.318/329.656/11.807 ms


"DNS/Networking Errors inside the docker"

[root@localhost ~]# docker -dns="" run centos:6.4 yum install hiphop-php
2013/08/21 07:53:05 POST /v1.4/containers/create
2013/08/21 07:53:05 POST /v1.4/containers/6d9fef14bd1a/start
2013/08/21 07:53:05 POST /v1.4/containers/6d9fef14bd1a/attach?logs=1&stderr=1&stdout=1&stream=1
Loaded plugins: fastestmirror
Error: Cannot retrieve repository metadata (repomd.xml) for repository: base. Please verify its path and try again
Could not retrieve mirrorlist error was
14: PYCURL ERROR 6 - "Couldn't resolve host ''"

Please issue the following commands, so that docker and its environment will be reset and above issue will be taken care of.

pkill docker
iptables -t nat -F
ifconfig docker0 down
brctl delbr docker0
docker -d

CREDITS: Thanks to sciurus for doing the hardwork in creating the spec file for kernel-ml-aufs.

Monday, August 19, 2013

Installing Go Lang 1.1 on centos 6.4 *64-bit

UPDATE: 28/Apr/2014 - Golang package is now available on Fedora EPEL Repository. You can just configure EPEL repo and do a "yum install golang".

I have added go-lang package to the current repository. So you can try installing it using the following steps.

1. Install centos 6.x

2. Download and setup Fedora EPEL Repository

sudo yum install

(Step-3 not needed, if you are seeing this on Apr/2014)

3. Setup repository

cd /etc/yum.repos.d
sudo wget

4. Install go package

sudo yum install golang

5. Write a simple "hello world" program to get started with go

[nareshv@fallenangel tmp]$ cat hello.go
package main

import "fmt"

func main() {
    fmt.Println("Hello, World.")
[nareshv@fallenangel tmp]$ go run hello.go
Hello, World. 

6. Continue exploring go-lang, from here

(Note is not applicable if you are using golang from EPEL Repository)

Note: Please note that, go-lang is compiled without emacs support (to avoid pulling tons of packages) and with gcc-4.6.3.