Installo due VM in VirtualBox identiche (4C, 4Gb RAM, 32Gb HDD) con una versione minimale di Centos 7 aggiornata.

Aggiorno il kernel a 4.16 dal repository elrepo.

# rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
# rpm -Uvh http://www.elrepo.org/elrepo-release-7.0-3.el7.elrepo.noarch.rpm
# yum --disablerepo="*" --enablerepo="elrepo-kernel" list available
# yum --enablerepo=elrepo-kernel install kernel-ml kernel-ml-devel

Edito il file /etc/default/grub

GRUB_TIMEOUT=5
GRUB_DEFAULT=0
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL_OUTPUT="console"
GRUB_CMDLINE_LINUX="rd.lvm.lv=centos/root rd.lvm.lv=centos/swap crashkernel=auto rhgb quiet"
GRUB_DISABLE_RECOVERY="true"

Ed eseguo per attivare la modifica precedente.

# grub2-mkconfig -o /boot/grub2/grub.cfg

Aggiungo qualche pacchetto.

# yum install epel-release.noarch
# yum update
# yum group install "Development Tools"
# yum install bzip2 net-tools psmisc nmap acpid unzip

Modifico /etc/hosts sui due nodi.

192.168.254.83  nodeA.netlite.it nodeA
192.168.254.84  nodeB.netlite.it nodeB

Installo i numerosi pacchetti necessari al cluster.

# yum install pcs fence-agents-all -y

Aggiungo le regole di firewalling.

# firewall-cmd --permanent --add-service=high-availability
# firewall-cmd --add-service=high-availability
# firewall-cmd --list-service
dhcpv6-client ssh high-availability

Modifico la password dell’utente hacluster.

# passwd hacluster
Changing password for user hacluster.
New password:
BAD PASSWORD: The password is shorter than 8 characters
Retype new password:
passwd: all authentication tokens updated successfully.

Avvio i servizi.

# systemctl start pcsd.service
# systemctl enable pcsd.service

Autorizzo i nodi del cluster.

# pcs cluster auth nodeA.netlite.it nodeB.netlite.it
Username: hacluster
Password:
nodeA.netlite.it: Authorized
nodeB.netlite.it: Authorized

Inizializzo il cluster.

# pcs cluster setup --start --name ClusterTest nodeA.netlite.it                                                        nodeB.netlite.it
Destroying cluster on nodes: nodeA.netlite.it, nodeB.netlite.it...
nodeA.netlite.it: Stopping Cluster (pacemaker)...
nodeB.netlite.it: Stopping Cluster (pacemaker)...
nodeB.netlite.it: Successfully destroyed cluster
nodeA.netlite.it: Successfully destroyed cluster
Sending 'pacemaker_remote authkey' to 'nodeA.netlite.it', 'nodeB.netlite.it'
nodeA.netlite.it: successful distribution of the file 'pacemaker_remote authkey'
nodeB.netlite.it: successful distribution of the file 'pacemaker_remote authkey'
Sending cluster config files to the nodes...
nodeA.netlite.it: Succeeded
nodeB.netlite.it: Succeeded
Starting cluster on nodes: nodeA.netlite.it, nodeB.netlite.it...
nodeB.netlite.it: Starting Cluster...
nodeA.netlite.it: Starting Cluster...
Synchronizing pcsd certificates on nodes nodeA.netlite.it, nodeB.netlite.it...
nodeA.netlite.it: Success
nodeB.netlite.it: Success
Restarting pcsd on the nodes in order to reload the certificates...
nodeA.netlite.it: Success
nodeB.netlite.it: Success

Abilito il cluster.

# pcs cluster enable --all

Visualizzo lo stato.

# pcs cluster status
Cluster Status:
 Stack: corosync
 Current DC: nodeA.netlite.it (version 1.1.16-12.el7_4.8-94ff4df) - partition with quorum
 Last updated: Tue Apr  3 13:02:21 2018
 Last change: Tue Apr  3 13:00:43 2018 by hacluster via crmd on nodeA.netlite.it
 2 nodes configured
 0 resources configured
PCSD Status:
  nodeA.netlite.it: Online
  nodeB.netlite.it: Online

Status dettagliati.

# pcs status
Cluster name: ClusterTest
WARNING: no stonith devices and stonith-enabled is not false
Stack: corosync
Current DC: nodeA.netlite.it (version 1.1.16-12.el7_4.8-94ff4df) - partition with quorum
Last updated: Tue Apr  3 13:02:53 2018
Last change: Tue Apr  3 13:00:43 2018 by hacluster via crmd on nodeA.netlite.it
2 nodes configured
0 resources configured
Online: [ nodeA.netlite.it nodeB.netlite.it ]
No resources
Daemon Status:
  corosync: active/enabled
  pacemaker: active/enabled
  pcsd: active/enabled

Disabilito i device stonith (meglio non farlo ma per test è ok).

# pcs property set stonith-enabled=false

In caso sia necessario attivare i devices qui c’è un buon punto di partenza STONITH.

Configuro un FS.

# pcs resource create httpd_fs Filesystem device="/dev/mapper/vg_apache-lv_apache" directory="/var/www" fstype="ext4" --group apache

Configuro un VIP.

# pcs resource create httpd_vip IPaddr2 ip=192.168.12.100 cidr_netmask=24 --group apache

Configuro un servizio.

# firewall-cmd --add-service=http
# firewall-cmd --permanent --add-service=http
# pcs resource create httpd_ser apache configfile="/etc/httpd/conf/httpd.conf" statusurl="http://127.0.0.1/server-status" --group apache

Disabilita un nodo.

# pcs cluster stop nodeA.netlite.it

Comandi utili.

# pcs resource move apache nodeA.netlite.it
# pcs resource stop apache nodeB.netlite.it
# pcs resource disable apache nodeB.netlite.it
# pcs resource enable apache nodeB.netlite.it
# pcs resource restart apache

andrea