:compat-mode: legacy
= Installation =
== Install &DISTRO; &DISTRO_VERSION; ==
=== Boot the Install Image ===
Download the 4GB
http://isoredirect.centos.org/centos/7/isos/x86_64/CentOS-7-x86_64-DVD-1804.iso[&DISTRO;
&DISTRO_VERSION; DVD ISO]. Use the image to boot a virtual machine, or
burn it to a DVD or USB drive and boot a physical server from that.
After starting the installation, select your language and keyboard layout at
the welcome screen.
.&DISTRO; &DISTRO_VERSION; Installation Welcome Screen
image::images/Welcome.png["Welcome to &DISTRO; &DISTRO_VERSION;",align="center",scaledwidth="100%"]
=== Installation Options ===
At this point, you get a chance to tweak the default installation options.
.&DISTRO; &DISTRO_VERSION; Installation Summary Screen
image::images/Installer.png["&DISTRO; &DISTRO_VERSION; Installation Summary",align="center",scaledwidth="100%"]
Ignore the *SOFTWARE SELECTION* section (try saying that 10 times quickly). The
*Infrastructure Server* environment does have add-ons with much of the software
we need, but we will leave it as a *Minimal Install* here, so that we can see
exactly what software is required later.
=== Configure Network ===
In the *NETWORK & HOSTNAME* section:
- Edit *Host Name:* as desired. For this example, we will use
*pcmk-1.localdomain*.
- Select your network device, press *Configure...*, and manually assign a fixed
IP address. For this example, we'll use 192.168.122.101 under *IPv4 Settings*
(with an appropriate netmask, gateway and DNS server).
- Flip the switch to turn your network device on, and press *Done*.
.&DISTRO; &DISTRO_VERSION; Network Interface Screen
image::images/Editing-eth0.png["&DISTRO; &DISTRO_VERSION; Editing eth0",align="center",scaledwidth="100%"]
[IMPORTANT]
===========
Do not accept the default network settings.
Cluster machines should never obtain an IP address via DHCP, because
DHCP's periodic address renewal will interfere with corosync.
===========
=== Configure Disk ===
By default, the installer's automatic partitioning will use LVM (which allows
us to dynamically change the amount of space allocated to a given partition).
However, it allocates all free space to the +/+ (aka. *root*) partition, which
cannot be reduced in size later (dynamic increases are fine).
In order to follow the DRBD and GFS2 portions of this guide, we need to reserve
space on each machine for a replicated volume.
Enter the *INSTALLATION DESTINATION* section, ensure the hard drive you want to
install to is selected, select *I will configure partitioning*, and press *Done*.
In the *MANUAL PARTITIONING* screen that comes next, click the option to create
mountpoints automatically. Select the +/+ mountpoint, and reduce the desired
capacity by 1GiB or so. Select *Modify...* by the volume group name, and change
the *Size policy:* to *As large as possible*, to make the reclaimed space
available inside the LVM volume group. We'll add the additional volume later.
.&DISTRO; &DISTRO_VERSION; Manual Partitioning Screen
image::images/Partitioning.png["&DISTRO; &DISTRO_VERSION; Partitioning",align="center",scaledwidth="100%"]
Press *Done*, then *Accept changes*.
=== Configure Time Synchronization ===
It is highly recommended to enable NTP on your cluster nodes. Doing so
ensures all nodes agree on the current time and makes reading log files
significantly easier.
&DISTRO; will enable NTP automatically. If you want to change any time-related
settings (such as time zone or NTP server), you can do this in the
*TIME & DATE* section.
=== Finish Install ===
Select *Begin Installation*. Once it completes, set a root password, and reboot
as instructed. For the purposes of this document, it is not necessary to create
any additional users. After the node reboots, you'll see a login prompt on
the console. Login using *root* and the password you created earlier.
.&DISTRO; &DISTRO_VERSION; Console Prompt
image::images/Console.png["&DISTRO; &DISTRO_VERSION; Console",align="center",scaledwidth="100%"]
[NOTE]
======
From here on, we're going to be working exclusively from the terminal.
======
== Configure the OS ==
=== Verify Networking ===
Ensure that the machine has the static IP address you configured earlier.
-----
[root@pcmk-1 ~]# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
link/ether 52:54:00:8e:eb:41 brd ff:ff:ff:ff:ff:ff
inet 192.168.122.101/24 brd 192.168.122.255 scope global noprefixroute eth0
valid_lft forever preferred_lft forever
inet6 fe80::e45:c99b:34c0:c657/64 scope link noprefixroute
valid_lft forever preferred_lft forever
-----
[NOTE]
=====
If you ever need to change the node's IP address from the command line, follow
these instructions, replacing *${device}* with the name of your network device:
....
[root@pcmk-1 ~]# vi /etc/sysconfig/network-scripts/ifcfg-${device} # manually edit as desired
[root@pcmk-1 ~]# nmcli dev disconnect ${device}
[root@pcmk-1 ~]# nmcli con reload ${device}
[root@pcmk-1 ~]# nmcli con up ${device}
....
This makes *NetworkManager* aware that a change was made on the config file.
=====
Next, ensure that the routes are as expected:
-----
[root@pcmk-1 ~]# ip route
default via 192.168.122.1 dev eth0 proto static metric 100
192.168.122.0/24 dev eth0 proto kernel scope link src 192.168.122.101 metric 100
-----
If there is no line beginning with *default via*, then you may need to add a line such as
[source,Bash]
GATEWAY="192.168.122.1"
to the device configuration using the same process as described above for
changing the IP address.
Now, check for connectivity to the outside world. Start small by
testing whether we can reach the gateway we configured.
-----
[root@pcmk-1 ~]# ping -c 1 192.168.122.1
PING 192.168.122.1 (192.168.122.1) 56(84) bytes of data.
64 bytes from 192.168.122.1: icmp_seq=1 ttl=64 time=0.254 ms
--- 192.168.122.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.254/0.254/0.254/0.000 ms
-----
Now try something external; choose a location you know should be available.
-----
[root@pcmk-1 ~]# ping -c 1 www.clusterlabs.org
PING oss-uk-1.clusterlabs.org (109.74.197.241) 56(84) bytes of data.
64 bytes from oss-uk-1.clusterlabs.org (109.74.197.241): icmp_seq=1 ttl=49 time=333 ms
--- oss-uk-1.clusterlabs.org ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 333.204/333.204/333.204/0.000 ms
-----
=== Login Remotely ===
The console isn't a very friendly place to work from, so we will now
switch to accessing the machine remotely via SSH where we can
use copy and paste, etc.
From another host, check whether we can see the new host at all:
-----
beekhof@f16 ~ # ping -c 1 192.168.122.101
PING 192.168.122.101 (192.168.122.101) 56(84) bytes of data.
64 bytes from 192.168.122.101: icmp_req=1 ttl=64 time=1.01 ms
--- 192.168.122.101 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.012/1.012/1.012/0.000 ms
-----
Next, login as root via SSH.
-----
beekhof@f16 ~ # ssh -l root 192.168.122.101
The authenticity of host '192.168.122.101 (192.168.122.101)' can't be established.
ECDSA key fingerprint is 6e:b7:8f:e2:4c:94:43:54:a8:53:cc:20:0f:29:a4:e0.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.122.101' (ECDSA) to the list of known hosts.
root@192.168.122.101's password:
Last login: Tue Aug 11 13:14:39 2015
[root@pcmk-1 ~]#
-----
=== Apply Updates ===
Apply any package updates released since your installation image was created:
----
[root@pcmk-1 ~]# yum update
----
=== Use Short Node Names ===
During installation, we filled in the machine's fully qualified domain
name (FQDN), which can be rather long when it appears in cluster logs and
status output. See for yourself how the machine identifies itself:
(((Nodes, short name)))
----
[root@pcmk-1 ~]# uname -n
pcmk-1.localdomain
----
(((Nodes, Domain name (Query))))
We can use the `hostnamectl` tool to strip off the domain name:
----
[root@pcmk-1 ~]# hostnamectl set-hostname $(uname -n | sed s/\\..*//)
----
(((Nodes, Domain name (Remove from host name))))
Now, check that the machine is using the correct name:
----
[root@pcmk-1 ~]# uname -n
pcmk-1
----
You may want to reboot to ensure all updates take effect.
== Repeat for Second Node ==
Repeat the Installation steps so far, so that you have two
nodes ready to have the cluster software installed.
For the purposes of this document, the additional node is called
pcmk-2 with address 192.168.122.102.
== Configure Communication Between Nodes ==
=== Configure Host Name Resolution ===
Confirm that you can communicate between the two new nodes:
----
[root@pcmk-1 ~]# ping -c 3 192.168.122.102
PING 192.168.122.102 (192.168.122.102) 56(84) bytes of data.
64 bytes from 192.168.122.102: icmp_seq=1 ttl=64 time=0.343 ms
64 bytes from 192.168.122.102: icmp_seq=2 ttl=64 time=0.402 ms
64 bytes from 192.168.122.102: icmp_seq=3 ttl=64 time=0.558 ms
--- 192.168.122.102 ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2000ms
rtt min/avg/max/mdev = 0.343/0.434/0.558/0.092 ms
----
Now we need to make sure we can communicate with the machines by their
name. If you have a DNS server, add additional entries for the two
machines. Otherwise, you'll need to add the machines to +/etc/hosts+
on both nodes. Below are the entries for my cluster nodes:
----
[root@pcmk-1 ~]# grep pcmk /etc/hosts
192.168.122.101 pcmk-1.clusterlabs.org pcmk-1
192.168.122.102 pcmk-2.clusterlabs.org pcmk-2
----
We can now verify the setup by again using ping:
----
[root@pcmk-1 ~]# ping -c 3 pcmk-2
PING pcmk-2.clusterlabs.org (192.168.122.101) 56(84) bytes of data.
64 bytes from pcmk-1.clusterlabs.org (192.168.122.101): icmp_seq=1 ttl=64 time=0.164 ms
64 bytes from pcmk-1.clusterlabs.org (192.168.122.101): icmp_seq=2 ttl=64 time=0.475 ms
64 bytes from pcmk-1.clusterlabs.org (192.168.122.101): icmp_seq=3 ttl=64 time=0.186 ms
--- pcmk-2.clusterlabs.org ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2001ms
rtt min/avg/max/mdev = 0.164/0.275/0.475/0.141 ms
----
=== Configure SSH ===
SSH is a convenient and secure way to copy files and perform commands
remotely. For the purposes of this guide, we will create a key without a
password (using the -N option) so that we can perform remote actions
without being prompted.
(((SSH)))
[WARNING]
=========
Unprotected SSH keys (those without a password) are not recommended for servers exposed to the outside world.
We use them here only to simplify the demo.
=========
Create a new key and allow anyone with that key to log in:
.Creating and Activating a new SSH Key
----
[root@pcmk-1 ~]# ssh-keygen -t dsa -f ~/.ssh/id_dsa -N ""
Generating public/private dsa key pair.
Your identification has been saved in /root/.ssh/id_dsa.
Your public key has been saved in /root/.ssh/id_dsa.pub.
The key fingerprint is:
91:09:5c:82:5a:6a:50:08:4e:b2:0c:62:de:cc:74:44 root@pcmk-1.clusterlabs.org
The key's randomart image is:
+--[ DSA 1024]----+
|==.ooEo.. |
|X O + .o o |
| * A + |
| + . |
| . S |
| |
| |
| |
| |
+-----------------+
[root@pcmk-1 ~]# cp ~/.ssh/id_dsa.pub ~/.ssh/authorized_keys
----
(((Creating and Activating a new SSH Key)))
Install the key on the other node:
----
[root@pcmk-1 ~]# scp -r ~/.ssh pcmk-2:
The authenticity of host 'pcmk-2 (192.168.122.102)' can't be established.
ECDSA key fingerprint is SHA256:63xNPkPYq98rYznf3T9QYJAzlaGiAsSgFVNHOZjPWqc.
ECDSA key fingerprint is MD5:d9:bf:6e:32:88:be:47:3d:96:f1:96:27:65:05:0b:c3.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added 'pcmk-2,192.168.122.102' (ECDSA) to the list of known hosts.
root@pcmk-2's password:
id_dsa
id_dsa.pub
authorized_keys
known_hosts
----
Test that you can now run commands remotely, without being prompted:
----
[root@pcmk-1 ~]# ssh pcmk-2 -- uname -n
pcmk-2
----