diff --git a/doc/Clusters_from_Scratch/en-US/Ch-Active-Active.txt b/doc/Clusters_from_Scratch/en-US/Ch-Active-Active.txt
index fd78f711ef..05f31e24d0 100644
--- a/doc/Clusters_from_Scratch/en-US/Ch-Active-Active.txt
+++ b/doc/Clusters_from_Scratch/en-US/Ch-Active-Active.txt
@@ -1,381 +1,382 @@
= Convert Cluster to Active/Active =
The primary requirement for an Active/Active cluster is that the data
required for your services is available, simultaneously, on both
machines. Pacemaker makes no requirement on how this is achieved; you
could use a SAN if you had one available, but since DRBD supports
multiple Primaries, we can continue to use it here.
== Install Cluster Filesystem Software ==
The only hitch is that we need to use a cluster-aware filesystem. The
one we used earlier with DRBD, xfs, is not one of those. Both OCFS2
and GFS2 are supported; here, we will use GFS2.
On both nodes, install the GFS2 command-line utilities and the
Distributed Lock Manager (DLM) required by cluster filesystems:
----
# yum install -y gfs2-utils dlm
----
== Configure the Cluster for the DLM ==
The DLM needs to run on both nodes, so we'll start by creating a resource for
it (using the *ocf:pacemaker:controld* resource script), and clone it:
----
[root@pcmk-1 ~]# pcs cluster cib dlm_cfg
[root@pcmk-1 ~]# pcs -f dlm_cfg resource create dlm ocf:pacemaker:controld op monitor interval=60s
[root@pcmk-1 ~]# pcs -f dlm_cfg resource clone dlm clone-max=2 clone-node-max=1
[root@pcmk-1 ~]# pcs -f dlm_cfg resource show
ClusterIP (ocf::heartbeat:IPaddr2): Started
WebSite (ocf::heartbeat:apache): Started
Master/Slave Set: WebDataClone [WebData]
Masters: [ pcmk-2 ]
Slaves: [ pcmk-1 ]
WebFS (ocf::heartbeat:Filesystem): Started
Clone Set: dlm-clone [dlm]
Stopped: [ pcmk-1 pcmk-2 ]
----
Activate our new configuration, and see how the cluster responds:
----
[root@pcmk-1 ~]# pcs cluster cib-push dlm_cfg
CIB updated
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Sat Dec 20 21:53:44 2014
Last change: Sat Dec 20 21:53:40 2014
Stack: corosync
Current DC: pcmk-1 (1) - partition with quorum
Version: 1.1.12-a9c8177
2 Nodes configured
8 Resources configured
Online: [ pcmk-1 pcmk-2 ]
Full list of resources:
ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2
WebSite (ocf::heartbeat:apache): Started pcmk-2
Master/Slave Set: WebDataClone [WebData]
Masters: [ pcmk-2 ]
Slaves: [ pcmk-1 ]
WebFS (ocf::heartbeat:Filesystem): Started pcmk-2
ipmi-fencing (stonith:fence_ipmilan): Started pcmk-1
Clone Set: dlm-clone [dlm]
Started: [ pcmk-1 pcmk-2 ]
PCSD Status:
pcmk-1: Online
pcmk-2: Online
Daemon Status:
corosync: active/disabled
pacemaker: active/disabled
pcsd: active/enabled
----
[[GFS2_prep]]
== Create and Populate GFS2 Filesystem ==
Before we do anything to the existing partition, we need to make sure it
is unmounted. We do this by telling the cluster to stop the WebFS resource.
This will ensure that other resources (in our case, Apache) using WebFS
are not only stopped, but stopped in the correct order.
----
[root@pcmk-1 ~]# pcs resource disable WebFS
[root@pcmk-1 ~]# pcs resource
ClusterIP (ocf::heartbeat:IPaddr2): Started
WebSite (ocf::heartbeat:apache): Stopped
Master/Slave Set: WebDataClone [WebData]
Masters: [ pcmk-2 ]
Slaves: [ pcmk-1 ]
WebFS (ocf::heartbeat:Filesystem): Stopped
Clone Set: dlm-clone [dlm]
Started: [ pcmk-1 pcmk-2 ]
----
You can see that both Apache and WebFS have been stopped,
and that *pcmk-2* is the current master for the DRBD device.
Now we can create a new GFS2 filesystem on the DRBD device.
[WARNING]
=========
This will erase all previous content stored on the DRBD device. Ensure
you have a copy of any important data.
=========
[IMPORTANT]
===========
Run the next command on whichever node has the DRBD Primary role.
Otherwise, you will receive the message:
-----
/dev/drbd1: Read-only file system
-----
===========
-----
[root@pcmk-2 ~]# mkfs.gfs2 -p lock_dlm -j 2 -t mycluster:web /dev/drbd1
It appears to contain an existing filesystem (xfs)
This will destroy any data on /dev/drbd1
Are you sure you want to proceed? [y/n]y
Device: /dev/drbd1
Block size: 4096
Device size: 1.00 GB (262127 blocks)
Filesystem size: 1.00 GB (262126 blocks)
Journals: 2
Resource groups: 5
Locking protocol: "lock_dlm"
Lock table: "mycluster:web"
UUID: 9a72c488-d8a7-24c9-ceee-add7a8ca52c2
-----
The `mkfs.gfs2` command required a number of additional parameters:
* `-p lock_dlm` specifies that we want to use the
kernel's DLM.
* `-j 2` indicates that the filesystem should reserve enough
space for two journals (one for each node that will access the filesystem).
* `-t mycluster:web` specifies the lock table name. The format for
this field is +pass:[<replaceable>clustername:fsname</replaceable>]+. For
+pass:[<replaceable>clustername</replaceable>]+, we need to use the same
value we specified originally with `pcs cluster setup --name` (which is also
the value of *cluster_name* in +/etc/corosync/corosync.conf+).
If you are unsure what your cluster name is, you can look in
+/etc/corosync/corosync.conf+ or execute the command
`pcs cluster corosync pcmk-1 | grep cluster_name`.
Now we can (re-)populate the new filesystem with data
(web pages). We'll create yet another variation on our home page.
-----
[root@pcmk-2 ~]# mount /dev/drbd1 /mnt
[root@pcmk-2 ~]# cat <<-END >/mnt/index.html
<html>
<body>My Test Site - GFS2</body>
</html>
END
+[root@pcmk-2 ~]# chcon -R --reference=/var/www/html /mnt
[root@pcmk-2 ~]# umount /dev/drbd1
[root@pcmk-2 ~]# drbdadm verify wwwdata
-----
== Reconfigure the Cluster for GFS2 ==
With the WebFS resource stopped, let's update the configuration.
----
[root@pcmk-1 ~]# pcs resource show WebFS
Resource: WebFS (class=ocf provider=heartbeat type=Filesystem)
Attributes: device=/dev/drbd1 directory=/var/www/html fstype=xfs
Meta Attrs: target-role=Stopped
Operations: start interval=0s timeout=60 (WebFS-start-timeout-60)
stop interval=0s timeout=60 (WebFS-stop-timeout-60)
monitor interval=20 timeout=40 (WebFS-monitor-interval-20)
----
The fstype option needs to be updated to *gfs2* instead of *xfs*.
----
[root@pcmk-1 ~]# pcs resource update WebFS fstype=gfs2
[root@pcmk-1 ~]# pcs resource show WebFS
Resource: WebFS (class=ocf provider=heartbeat type=Filesystem)
Attributes: device=/dev/drbd1 directory=/var/www/html fstype=gfs2
Meta Attrs: target-role=Stopped
Operations: start interval=0s timeout=60 (WebFS-start-timeout-60)
stop interval=0s timeout=60 (WebFS-stop-timeout-60)
monitor interval=20 timeout=40 (WebFS-monitor-interval-20)
----
GFS2 requires that DLM be running, so we also need to set up new colocation
and ordering constraints for it:
----
[root@pcmk-1 ~]# pcs constraint colocation add WebFS with dlm-clone INFINITY
[root@pcmk-1 ~]# pcs constraint order dlm-clone then WebFS
Adding dlm-clone WebFS (kind: Mandatory) (Options: first-action=start then-action=start)
----
== Clone the IP address ==
There's no point making the services active on both locations if we can't
reach them both, so let's clone the IP address.
The *IPaddr2* resource agent has built-in intelligence for when it is configured
as a clone. It will utilize a multicast MAC address to have the local switch
send the relevant packets to all nodes in the cluster, together with *iptables
clusterip* rules on the nodes so that any given packet will be grabbed by
exactly one node. This will give us a simple but effective form of
load-balancing requests between our two nodes.
Let's start a new config, and clone our IP:
----
[root@pcmk-1 ~]# pcs cluster cib loadbalance_cfg
[root@pcmk-1 ~]# pcs -f loadbalance_cfg resource clone ClusterIP \
clone-max=2 clone-node-max=2 globally-unique=true
----
* `clone-max=2` tells the resource agent to split packets this many ways. This
should equal the number of nodes that can host the IP.
* `clone-node-max=2` says that one node can run up to 2 instances
of the clone. This should also equal the number of nodes that can
host the IP, so that if any node goes down, another node can take over
the failed node's "request bucket". Otherwise, requests intended for
the failed node would be discarded.
* `globally-unique=true` tells the cluster that one clone isn't identical
to another (each handles a different "bucket"). This also tells the resource
agent to insert *iptables* rules so each host only processes packets in its
bucket(s).
Notice that when the ClusterIP becomes a clone, the constraints
referencing ClusterIP now reference the clone. This is
done automatically by pcs.
----
[root@pcmk-1 ~]# pcs -f loadbalance_cfg constraint
Location Constraints:
Ordering Constraints:
start ClusterIP-clone then start WebSite (kind:Mandatory)
promote WebDataClone then start WebFS (kind:Mandatory)
start WebFS then start WebSite (kind:Mandatory)
start dlm-clone then start WebFS (kind:Mandatory)
Colocation Constraints:
WebSite with ClusterIP-clone (score:INFINITY)
WebFS with WebDataClone (score:INFINITY) (with-rsc-role:Master)
WebSite with WebFS (score:INFINITY)
WebFS with dlm-clone (score:INFINITY)
----
Now we must tell the resource how to decide which requests are
processed by which hosts. To do this, we specify the *clusterip_hash* parameter.
The value of *sourceip* means that the source IP address of incoming packets
will be hashed; each node will process a certain range of hashes.
----
[root@pcmk-1 ~]# pcs -f loadbalance_cfg resource update ClusterIP clusterip_hash=sourceip
----
Load our configuration to the cluster, and see how it responds.
-----
[root@pcmk-1 ~]# pcs cluster cib-push loadbalance_cfg
CIB updated
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Sat Dec 20 22:05:48 2014
Last change: Sat Dec 20 22:05:34 2014
Stack: corosync
Current DC: pcmk-1 (1) - partition with quorum
Version: 1.1.12-a9c8177
2 Nodes configured
9 Resources configured
Online: [ pcmk-1 pcmk-2 ]
Full list of resources:
WebSite (ocf::heartbeat:apache): Stopped
Master/Slave Set: WebDataClone [WebData]
Masters: [ pcmk-1 ]
Slaves: [ pcmk-2 ]
WebFS (ocf::heartbeat:Filesystem): Stopped
ipmi-fencing (stonith:fence_ipmilan): Started pcmk-1
Clone Set: dlm-clone [dlm]
Started: [ pcmk-1 pcmk-2 ]
Clone Set: ClusterIP-clone [ClusterIP] (unique)
ClusterIP:0 (ocf::heartbeat:IPaddr2): Started pcmk-1
ClusterIP:1 (ocf::heartbeat:IPaddr2): Started pcmk-2
PCSD Status:
pcmk-1: Online
pcmk-2: Online
Daemon Status:
corosync: active/disabled
pacemaker: active/disabled
pcsd: active/enabled
-----
If desired, you can demonstrate that all request buckets are working
by using a tool such as `arping` from several source hosts
to see which host responds to each.
== Clone the Filesystem and Apache Resources ==
Now that we have a cluster filesystem ready to go,
and our nodes can load-balance requests to a shared IP address,
we can configure the cluster so both nodes mount the filesystem
and respond to web requests.
Clone the filesystem and Apache resources in a new configuration.
Notice how pcs automatically updates the relevant constraints again.
----
[root@pcmk-1 ~]# pcs cluster cib active_cfg
[root@pcmk-1 ~]# pcs -f active_cfg resource clone WebFS
[root@pcmk-1 ~]# pcs -f active_cfg resource clone WebSite
[root@pcmk-1 ~]# pcs -f active_cfg constraint
Location Constraints:
Ordering Constraints:
start ClusterIP-clone then start WebSite-clone (kind:Mandatory)
promote WebDataClone then start WebFS-clone (kind:Mandatory)
start WebFS-clone then start WebSite-clone (kind:Mandatory)
start dlm-clone then start WebFS-clone (kind:Mandatory)
Colocation Constraints:
WebSite-clone with ClusterIP-clone (score:INFINITY)
WebFS-clone with WebDataClone (score:INFINITY) (with-rsc-role:Master)
WebSite-clone with WebFS-clone (score:INFINITY)
WebFS-clone with dlm-clone (score:INFINITY)
----
Tell the cluster that it is now allowed to promote both instances to be DRBD
Primary (aka. master).
-----
[root@pcmk-1 ~]# pcs -f active_cfg resource update WebDataClone master-max=2
-----
Finally, load our configuration to the cluster, and re-enable the WebFS resource
(which we disabled earlier).
-----
[root@pcmk-1 ~]# pcs cluster cib-push active_cfg
CIB updated
[root@pcmk-1 ~]# pcs resource enable WebFS
-----
After all the processes are started, the status should look similar to this.
-----
[root@pcmk-1 ~]# pcs resource
Master/Slave Set: WebDataClone [WebData]
Masters: [ pcmk-1 pcmk-2 ]
Clone Set: dlm-clone [dlm]
Started: [ pcmk-1 pcmk-2 ]
Clone Set: ClusterIP-clone [ClusterIP] (unique)
ClusterIP:0 (ocf::heartbeat:IPaddr2): Started
ClusterIP:1 (ocf::heartbeat:IPaddr2): Started
Clone Set: WebFS-clone [WebFS]
Started: [ pcmk-1 pcmk-2 ]
Clone Set: WebSite-clone [WebSite]
Started: [ pcmk-1 pcmk-2 ]
-----
== Test Failover ==
Testing failover is left as an exercise for the reader.
For example, you can put one node into standby mode,
use `pcs status` to confirm that its ClusterIP clone was
moved to the other node, and use `arping` to verify that
packets are not being lost from any source host.
[NOTE]
====
You may find that when a failed node rejoins the cluster,
both ClusterIP clones stay on one node, due to the
resource stickiness. While this works fine, it effectively eliminates
load-balancing and returns the cluster to an active-passive setup again.
You can avoid this by disabling stickiness for the IP address resource:
----
[root@pcmk-1 ~]# pcs resource meta ClusterIP resource-stickiness=0
----
====
diff --git a/doc/Clusters_from_Scratch/en-US/Ch-Apache.txt b/doc/Clusters_from_Scratch/en-US/Ch-Apache.txt
index 567b7f4ff5..87f761aa88 100644
--- a/doc/Clusters_from_Scratch/en-US/Ch-Apache.txt
+++ b/doc/Clusters_from_Scratch/en-US/Ch-Apache.txt
@@ -1,428 +1,430 @@
= Add Apache as a Cluster Service =
Now that we have a basic but functional active/passive two-node cluster,
we're ready to add some real services. We're going to start with Apache
because it is a feature of many clusters and relatively simple to
configure.
== Install Apache ==
Before continuing, we need to make sure Apache is installed on both
hosts. We also need the wget tool in order for the cluster to be able to check
the status of the Apache server.
----
# yum install -y httpd wget
+# firewall-cmd --permanent --add-service=http
+# firewall-cmd --reload
----
[IMPORTANT]
====
Do *not* enable the httpd service. Services that are intended to
be managed via the cluster software should never be managed by the OS.
It is often useful, however, to manually start the service, verify that
it works, then stop it again, before adding it to the cluster. This
allows you to resolve any non-cluster-related problems before continuing.
Since this is a simple example, we'll skip that step here.
====
== Create Website Documents ==
We need to create a page for Apache to serve. On &DISTRO; &DISTRO_VERSION;, the
default Apache document root is /var/www/html, so we'll create an index file
there. For the moment, we will simplify things by serving a static site
and manually synchronizing the data between the two nodes, so run this command
on both nodes:
-----
# cat <<-END >/var/www/html/index.html
<html>
<body>My Test Site - $(hostname)</body>
</html>
END
-----
== Enable the Apache status URL ==
In order to monitor the health of your Apache instance, and recover it if
it fails, the resource agent used by Pacemaker assumes the server-status
URL is available. On both nodes, enable the URL with:
----
# cat <<-END >/etc/httpd/conf.d/status.conf
<Location /server-status>
SetHandler server-status
Order deny,allow
Deny from all
Allow from 127.0.0.1
</Location>
END
----
[NOTE]
======
If you are using a different operating system, server-status may already be
enabled or may be configurable in a different location.
======
== Configure the Cluster ==
At this point, Apache is ready to go, and all that needs to be done is to
add it to the cluster. Let's call the resource WebSite. We need to use
an OCF resource script called apache in the heartbeat namespace.
footnote:[Compare the key used here, *ocf:heartbeat:apache*, with the one we
used earlier for the IP address, *ocf:heartbeat:IPaddr2*]
The script's only required parameter is the path to the main Apache
configuration file, and we'll tell the cluster to check once a
minute that Apache is still running.
----
[root@pcmk-1 ~]# pcs resource create WebSite ocf:heartbeat:apache \
configfile=/etc/httpd/conf/httpd.conf \
statusurl="http://localhost/server-status" \
op monitor interval=1min
----
By default, the operation timeout for all resources' start, stop, and monitor
operations is 20 seconds. In many cases, this timeout period is less than
a particular resource's advised timeout period. For the purposes of this
tutorial, we will adjust the global operation timeout default to 240 seconds.
----
[root@pcmk-1 ~]# pcs resource op defaults timeout=240s
[root@pcmk-1 ~]# pcs resource op defaults
timeout: 240s
----
[NOTE]
======
In a production cluster, it is usually better to adjust each resource's
start, stop, and monitor timeouts to values that are appropriate to
the behavior observed in your environment, rather than adjust
the global default.
======
After a short delay, we should see the cluster start Apache.
-----
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 12:40:41 2014
Last change: Wed Dec 17 12:40:05 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a9c8177
2 Nodes configured
2 Resources configured
Online: [ pcmk-1 pcmk-2 ]
Full list of resources:
ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2
WebSite (ocf::heartbeat:apache): Started pcmk-1
PCSD Status:
pcmk-1: Online
pcmk-2: Online
Daemon Status:
corosync: active/disabled
pacemaker: active/disabled
pcsd: active/enabled
-----
Wait a moment, the WebSite resource isn't running on the same host as our
IP address!
[NOTE]
======
If, in the `pcs status` output, you see the WebSite resource has
failed to start, then you've likely not enabled the status URL correctly.
You can check whether this is the problem by running:
....
wget -O - http://127.0.0.1/server-status
....
If you see *Connection refused* in the output, then this is likely the
problem. Ensure that *Allow from 127.0.0.1* is present for
the *<Location /server-status>* block.
======
== Ensure Resources Run on the Same Host ==
To reduce the load on any one machine, Pacemaker will generally try to
spread the configured resources across the cluster nodes. However, we
can tell the cluster that two resources are related and need to run on
the same host (or not at all). Here, we instruct the cluster that
WebSite can only run on the host that ClusterIP is active on.
To achieve this, we use a _colocation constraint_ that indicates it is
mandatory for WebSite to run on the same node as ClusterIP. The
"mandatory" part of the colocation constraint is indicated by using a
score of INFINITY. The INFINITY score also means that if ClusterIP is not
active anywhere, WebSite will not be permitted to run.
[NOTE]
=======
If ClusterIP is not active anywhere, WebSite will not be permitted to run
anywhere.
=======
[IMPORTANT]
===========
Colocation constraints are "directional", in that they imply certain
things about the order in which the two resources will have a location
chosen. In this case, we're saying that *WebSite* needs to be placed on the
same machine as *ClusterIP*, which implies that the cluster must know the
location of *ClusterIP* before choosing a location for *WebSite*.
===========
-----
[root@pcmk-1 ~]# pcs constraint colocation add WebSite with ClusterIP INFINITY
[root@pcmk-1 ~]# pcs constraint
Location Constraints:
Ordering Constraints:
Colocation Constraints:
WebSite with ClusterIP (score:INFINITY)
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 13:57:58 2014
Last change: Wed Dec 17 13:57:22 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a9c8177
2 Nodes configured
2 Resources configured
Online: [ pcmk-1 pcmk-2 ]
Full list of resources:
ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2
WebSite (ocf::heartbeat:apache): Started pcmk-2
PCSD Status:
pcmk-1: Online
pcmk-2: Online
Daemon Status:
corosync: active/disabled
pacemaker: active/disabled
pcsd: active/enabled
-----
== Ensure Resources Start and Stop in Order ==
Like many services, Apache can be configured to bind to specific
IP addresses on a host or to the wildcard IP address. If Apache
binds to the wildcard, it doesn't matter whether an IP address
is added before or after Apache starts; Apache will respond on
that IP just the same. However, if Apache binds only to certain IP
address(es), the order matters: If the address is added after Apache
starts, Apache won't respond on that address.
To be sure our WebSite responds regardless of Apache's address configuration,
we need to make sure ClusterIP not only runs on the same node,
but starts before WebSite. A colocation constraint only ensures the
resources run together, not the order in which they are started and stopped.
We do this by adding an ordering constraint. By default, all order constraints
are mandatory, which means that the recovery of ClusterIP will also trigger the
recovery of WebSite.
-----
[root@pcmk-1 ~]# pcs constraint order ClusterIP then WebSite
Adding ClusterIP WebSite (kind: Mandatory) (Options: first-action=start then-action=start)
[root@pcmk-1 ~]# pcs constraint
Location Constraints:
Ordering Constraints:
start ClusterIP then start WebSite (kind:Mandatory)
Colocation Constraints:
WebSite with ClusterIP (score:INFINITY)
-----
== Prefer One Node Over Another ==
Pacemaker does not rely on any sort of hardware symmetry between nodes,
so it may well be that one machine is more powerful than the other. In
such cases, it makes sense to host the resources on the more powerful node if
it is available. To do this, we create a location constraint.
In the location constraint below, we are saying the WebSite resource
prefers the node pcmk-1 with a score of 50. Here, the score indicates
how badly we'd like the resource to run at this location.
-----
[root@pcmk-1 ~]# pcs constraint location WebSite prefers pcmk-1=50
[root@pcmk-1 ~]# pcs constraint
Location Constraints:
Resource: WebSite
Enabled on: pcmk-1 (score:50)
Ordering Constraints:
start ClusterIP then start WebSite (kind:Mandatory)
Colocation Constraints:
WebSite with ClusterIP (score:INFINITY)
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 14:11:49 2014
Last change: Wed Dec 17 14:11:20 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a9c8177
2 Nodes configured
2 Resources configured
Online: [ pcmk-1 pcmk-2 ]
Full list of resources:
ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2
WebSite (ocf::heartbeat:apache): Started pcmk-2
PCSD Status:
pcmk-1: Online
pcmk-2: Online
Daemon Status:
corosync: active/disabled
pacemaker: active/disabled
pcsd: active/enabled
-----
Wait a minute, the resources are still on pcmk-2!
Even though WebSite now prefers to run on pcmk-1, that preference is
(intentionally) less than the resource stickiness (how much we
preferred not to have unnecessary downtime).
To see the current placement scores, you can use a tool called crm_simulate.
----
[root@pcmk-1 ~]# crm_simulate -sL
Current cluster status:
Online: [ pcmk-1 pcmk-2 ]
ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2
WebSite (ocf::heartbeat:apache): Started pcmk-2
Allocation scores:
native_color: ClusterIP allocation score on pcmk-1: 50
native_color: ClusterIP allocation score on pcmk-2: 200
native_color: WebSite allocation score on pcmk-1: -INFINITY
native_color: WebSite allocation score on pcmk-2: 100
Transition Summary:
----
== Move Resources Manually ==
There are always times when an administrator needs to override the
cluster and force resources to move to a specific location. In this example,
we will force the WebSite to move to pcmk-1 by
updating our previous location constraint with a score of INFINITY.
-----
[root@pcmk-1 ~]# pcs constraint location WebSite prefers pcmk-1=INFINITY
[root@pcmk-1 ~]# pcs constraint
Location Constraints:
Resource: WebSite
Enabled on: pcmk-1 (score:INFINITY)
Ordering Constraints:
start ClusterIP then start WebSite (kind:Mandatory)
Colocation Constraints:
WebSite with ClusterIP (score:INFINITY)
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 14:19:34 2014
Last change: Wed Dec 17 14:18:37 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a9c8177
2 Nodes configured
2 Resources configured
Online: [ pcmk-1 pcmk-2 ]
Full list of resources:
ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1
WebSite (ocf::heartbeat:apache): Started pcmk-1
PCSD Status:
pcmk-1: Online
pcmk-2: Online
Daemon Status:
corosync: active/disabled
pacemaker: active/disabled
pcsd: active/enabled
-----
Once we've finished whatever activity required us to move the
resources to pcmk-1 (in our case nothing), we can then allow the cluster
to resume normal operation by removing the new constraint. Since we previously
configured a default stickiness, the resources will remain on pcmk-1.
First, use the `--full` option to get the constraint's ID:
-----
[root@pcmk-1 ~]# pcs constraint --full
Location Constraints:
Resource: WebSite
Enabled on: pcmk-1 (score:INFINITY) (id:location-WebSite-pcmk-1-INFINITY)
Ordering Constraints:
start ClusterIP then start WebSite (kind:Mandatory) (id:order-ClusterIP-WebSite-mandatory)
Colocation Constraints:
WebSite with ClusterIP (score:INFINITY) (id:colocation-WebSite-ClusterIP-INFINITY)
-----
Then remove the desired contraint using its ID:
-----
[root@pcmk-1 ~]# pcs constraint remove location-WebSite-pcmk-1-INFINITY
[root@pcmk-1 ~]# pcs constraint
Location Constraints:
Ordering Constraints:
start ClusterIP then start WebSite (kind:Mandatory)
Colocation Constraints:
WebSite with ClusterIP (score:INFINITY)
-----
Note that the location constraint is now gone. If we check the cluster
status, we can also see that (as expected) the resources are still active
on pcmk-1.
-----
# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 14:25:21 2014
Last change: Wed Dec 17 14:24:29 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a9c8177
2 Nodes configured
2 Resources configured
Online: [ pcmk-1 pcmk-2 ]
Full list of resources:
ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1
WebSite (ocf::heartbeat:apache): Started pcmk-1
PCSD Status:
pcmk-1: Online
pcmk-2: Online
Daemon Status:
corosync: active/disabled
pacemaker: active/disabled
pcsd: active/enabled
-----
diff --git a/doc/Clusters_from_Scratch/en-US/Ch-Installation.txt b/doc/Clusters_from_Scratch/en-US/Ch-Installation.txt
index 486743cae5..41f32c4526 100644
--- a/doc/Clusters_from_Scratch/en-US/Ch-Installation.txt
+++ b/doc/Clusters_from_Scratch/en-US/Ch-Installation.txt
@@ -1,516 +1,508 @@
= Installation =
== Install &DISTRO; &DISTRO_VERSION; ==
Detailed instructions for installing Fedora are available at
http://docs.fedoraproject.org/en-US/Fedora/21/html/Installation_Guide/ in a number of
languages. The abbreviated version is as follows:
Point your browser to https://getfedora.org/,
choose a flavor (Server is an appropriate choice),
and download the installation image appropriate to your hardware.
Burn the installation image to a DVD or USB drive
footnote:[http://docs.fedoraproject.org/en-US/Fedora/21/html/Installation_Guide/sect-preparing-boot-media.html]
and boot from it, or use the image to boot a virtual machine.
After starting the installation, select your language and keyboard layout at
the welcome screen.
footnote:[http://docs.fedoraproject.org/en-US/Fedora/21/html/Installation_Guide/sect-installation-graphical-mode.html]
At this point, you get a chance to tweak the default installation options.
In the *NETWORK & HOSTNAME* section you'll want to:
- Assign your machine a host name.
I happen to control the clusterlabs.org domain name, so I will use
pcmk-1.clusterlabs.org here.
- Assign a fixed IPv4 address. In this example, I'll use 192.168.122.101.
[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.
If you miss this step during installation, it can easily be fixed later. You will have
to navigate to *system settings* and select *network*. From there, you can select
what device to configure.
===========
In the *Software Selection* section (try saying that 10 times
quickly), leave all *Add-Ons* unchecked so that we see everything that gets
installed. We'll install any extra software we need later.
[IMPORTANT]
===========
By default Fedora uses LVM for partitioning which allows us to
dynamically change the amount of space allocated to a given partition.
However, by default it also allocates all free space to the +/+
(aka. *root*) partition, which cannot be dynamically _reduced_ in size
(dynamic increases are fine, by the way).
So if you plan on following the DRBD or GFS2 portions of this guide,
you should reserve at least 1GiB of space on each machine from which to
create a shared volume. To do so, enter the *Installation
Destination* section where you are be given an opportunity to reduce
the size of the *root* partition (after choosing which hard drive you
wish to install to). If you want the reserved space to be available
within an LVM volume group, be sure to select *Modify...* next to
the volume group name and change the *Size policy:* to *Fixed*
or *As large as possible*.
===========
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. You can do this in the *DATE & TIME* section.
footnote:[http://docs.fedoraproject.org/en-US/Fedora/21/html/Installation_Guide/sect-installation-gui-date-and-time.html]
Once you've completed the installation, set a root password 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 (possibly mangled) login prompt on
the console. Login using *root* and the password you created earlier.
image::images/Console.png["Initial Console",align="center",scaledwidth="65%"]
[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
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
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:d7:d6:08 brd ff:ff:ff:ff:ff:ff
inet 192.168.122.101/24 brd 192.168.122.255 scope global eth0
valid_lft forever preferred_lft forever
inet6 fe80::5054:ff:fed7:d608/64 scope link
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 ~]# vim /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 1024
192.168.122.0/24 dev eth0 proto kernel scope link src 192.168.122.101
-----
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_req=1 ttl=64 time=0.249 ms
--- 192.168.122.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.249/0.249/0.249/0.000 ms
-----
Now try something external; choose a location you know should be available.
-----
[root@pcmk-1 ~]# ping -c 1 www.google.com
PING www.l.google.com (173.194.72.106) 56(84) bytes of data.
64 bytes from tf-in-f106.1e100.net (173.194.72.106): icmp_req=1 ttl=41 time=167 ms
--- www.l.google.com ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 167.618/167.618/167.618/0.000 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
----
-=== Disable Security During Testing ===
-
-To simplify this guide and focus on the aspects directly connected to
-clustering, we will now disable the machine's firewall and SELinux
-installation.
-
-[WARNING]
-===========
-These actions create significant security issues and should not be performed on
-machines that will be exposed to the outside world.
-===========
-
-////
- TODO: Create an Appendix that deals with (at least) re-enabling the firewall.
-////
-
-----
-[root@pcmk-1 ~]# setenforce 0
-[root@pcmk-1 ~]# sed -i.bak "s/SELINUX=enforcing/SELINUX=permissive/g" /etc/selinux/config
-[root@pcmk-1 ~]# systemctl disable firewalld.service
-[root@pcmk-1 ~]# systemctl stop firewalld.service
-[root@pcmk-1 ~]# iptables --flush
-----
-
-[NOTE]
-===========
-If you are using Fedora 17 or earlier or are using the iptables
-service for your firewall, the commands would be:
-
-----
-[root@pcmk-1 ~]# setenforce 0
-[root@pcmk-1 ~]# sed -i.bak "s/SELINUX=enforcing/SELINUX=permissive/g" /etc/selinux/config
-[root@pcmk-1 ~]# systemctl disable iptables.service
-[root@pcmk-1 ~]# rm -f /etc/systemd/system/basic.target.wants/iptables.service
-[root@pcmk-1 ~]# systemctl stop iptables.service
-[root@pcmk-1 ~]# iptables --flush
-----
-===========
-
-
=== 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.clusterlabs.org
[root@pcmk-1 ~]# dnsdomainname
clusterlabs.org
----
(((Nodes, Domain name (Query))))
The output from the second command is fine, but we really don't need the
domain name included in the basic host details. To address this, we need
to 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 the machine is using the correct names
----
[root@pcmk-1 ~]# uname -n
pcmk-1
[root@pcmk-1 ~]# dnsdomainname
clusterlabs.org
----
== 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 a4:f5:b2:34:9d:86:2b:34:a2:87:37:b9:ca:68:52:ec.
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.pub 100% 616 0.6KB/s 00:00
id_dsa 100% 672 0.7KB/s 00:00
known_hosts 100% 400 0.4KB/s 00:00
authorized_keys 100% 616 0.6KB/s 00:00
----
Test that you can now run commands remotely, without being prompted:
----
[root@pcmk-1 ~]# ssh pcmk-2 -- uname -n
pcmk-2
----
== Install the Cluster Software ==
Fire up a shell on both nodes and run the following to install pacemaker, and while
we're at it, some command-line tools to make our lives easier:
----
# yum install -y pacemaker pcs psmisc
----
[IMPORTANT]
===========
This document will show commands that need to be executed on both nodes
with a simple `#` prompt. Be sure to run them on each node individually.
===========
[NOTE]
===========
This document uses `pcs` for cluster management. Other alternatives,
such as `crmsh`, are available, but their syntax
will differ from the examples used here.
===========
== Configure the Cluster Software ==
+=== Allow cluster services through firewall ===
+
+On each node, allow cluster-related services through the local firewall:
+----
+# firewall-cmd --permanent --add-service=high-availability
+success
+# firewall-cmd --reload
+success
+----
+
+[NOTE]
+======
+If you are using iptables directly, or some other firewall solution besides
+firewalld, simply open the following ports, which can be used by various
+clustering components: TCP ports 2224, 3121, and 21064, and UDP port 5405.
+
+If you run into any problems during testing, you might want to disable
+the firewall and SELinux entirely until you have everything working.
+This may create significant security issues and should not be performed on
+machines that will be exposed to the outside world, but may be appropriate
+during development and testing on a protected host.
+
+To disable security measures:
+----
+[root@pcmk-1 ~]# setenforce 0
+[root@pcmk-1 ~]# sed -i.bak "s/SELINUX=enforcing/SELINUX=permissive/g" /etc/selinux/config
+[root@pcmk-1 ~]# systemctl disable firewalld.service
+[root@pcmk-1 ~]# systemctl stop firewalld.service
+[root@pcmk-1 ~]# iptables --flush
+----
+======
+
=== Enable pcs Daemon ===
Before the cluster can be configured, the pcs daemon must be started and enabled
to start at boot time on each node. This daemon works with the pcs command-line interface
to manage synchronizing the corosync configuration across all nodes in the cluster.
Start and enable the daemon by issuing the following commands on each node:
----
# systemctl start pcsd.service
# systemctl enable pcsd.service
ln -s '/usr/lib/systemd/system/pcsd.service' '/etc/systemd/system/multi-user.target.wants/pcsd.service'
----
The installed packages will create a *hacluster* user with a disabled password.
While this is fine for running `pcs` commands locally,
the account needs a login password in order to perform such tasks as syncing
the corosync configuration, or starting and stopping the cluster on other nodes.
This tutorial will make use of such commands,
so now we will set a password for the *hacluster* user, using the same password
on both nodes:
----
# passwd hacluster
Changing password for user hacluster.
New password:
Retype new password:
passwd: all authentication tokens updated successfully.
----
[NOTE]
===========
Alternatively, to script this process or set the password on a
different machine from the one you're logged into, you can use
the `--stdin` option for `passwd`:
----
[root@pcmk-1 ~]# ssh pcmk-2 -- 'echo redhat1 | passwd --stdin hacluster'
----
===========
=== Configure Corosync ===
On either node, use `pcs cluster auth` to authenticate as the *hacluster* user:
----
[root@pcmk-1 ~]# pcs cluster auth pcmk-1 pcmk-2
Username: hacluster
Password:
pcmk-1: Authorized
pcmk-2: Authorized
----
[IMPORTANT]
===========
The version of pcs shipped with Fedora 21 will bind only to
the host's IPv6 address in some circumstances. If you get errors
with `pcs cluster auth`, add this line before the first *server.run* line in
+/usr/lib/pcsd/ssl.rb+ to bind to IPv4 only:
----
webrick_options[:BindAddress] = '0.0.0.0'
----
And restart pcsd:
----
[root@pcmk-1 ~]# systemctl restart pcsd
----
This is a temporary workaround that will get removed if the pcsd
package is later updated.
===========
Next, use `pcs cluster setup` to generate and synchronize the corosync
configuration:
----
[root@pcmk-1 ~]# pcs cluster setup --name mycluster pcmk-1 pcmk-2
Shutting down pacemaker/corosync services...
Redirecting to /bin/systemctl stop pacemaker.service
Redirecting to /bin/systemctl stop corosync.service
Killing any remaining services...
Removing all cluster configuration files...
pcmk-1: Succeeded
pcmk-2: Succeeded
----
If you received an authorization error for either of those commands, make
sure you configured the *hacluster* user account on each node
with the same password.
[NOTE]
======
Early versions of pcs required that `--name` be omitted from the above command.
If you are not using `pcs` for cluster administration,
follow whatever procedures are appropriate for your tools
to create a corosync.conf and copy it to all nodes.
The `pcs` command will configure corosync to use UDP unicast transport; if you
choose to use multicast instead, choose a multicast address carefully.
footnote:[For some subtle issues, see the now-defunct http://web.archive.org/web/20101211210054/http://29west.com/docs/THPM/multicast-address-assignment.html or the more detailed treatment in
http://www.cisco.com/c/dam/en/us/support/docs/ip/ip-multicast/ipmlt_wp.pdf[Cisco's
Guidelines for Enterprise IP Multicast Address Allocation] paper.]
======
The final /etc/corosync.conf configuration on each node should look
something like the sample in <<ap-corosync-conf>>.
diff --git a/doc/Clusters_from_Scratch/en-US/Ch-Shared-Storage.txt b/doc/Clusters_from_Scratch/en-US/Ch-Shared-Storage.txt
index 58651e7f5d..7cea792111 100644
--- a/doc/Clusters_from_Scratch/en-US/Ch-Shared-Storage.txt
+++ b/doc/Clusters_from_Scratch/en-US/Ch-Shared-Storage.txt
@@ -1,508 +1,538 @@
= Replicate Storage Using DRBD =
Even if you're serving up static websites, having to manually synchronize
the contents of that website to all the machines in the cluster is not
ideal. For dynamic websites, such as a wiki, it's not even an option. Not
everyone care afford network-attached storage, but somehow the data needs
to be kept in sync.
Enter DRBD, which can be thought of as network-based RAID-1.
footnote:[See http://www.drbd.org/ for details.]
== Install the DRBD Packages ==
DRBD itself is included in the upstream kernel,
footnote:[Since version 2.6.33]
but we do need some utilities to use it effectively. On both nodes, run:
+DRBD will not be able to run under the default SELinux security policies.
+If you are familiar with SELinux, you can modify the policies in a more
+fine-grained manner, but here we will simply exempt DRBD processes from SELinux
+control:
----
# yum install -y drbd-pacemaker drbd-udev
+# semanage permissive -a drbd_t
----
+We will configure DRBD to use port 7789, so allow that port from each host to
+the other:
+----
+[root@pcmk-1 ~]# firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="192.168.122.102" port port="7789" protocol="tcp" accept'
+success
+[root@pcmk-1 ~]# firewall-cmd --reload
+success
+----
+----
+[root@pcmk-2 ~]# firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="192.168.122.101" port port="7789" protocol="tcp" accept'
+success
+[root@pcmk-2 ~]# firewall-cmd --reload
+success
+----
+
+[NOTE]
+======
+In this example, we have only two nodes, and all network traffic is on the same LAN.
+In production, it is recommended to use a dedicated, isolated network for cluster-related traffic,
+so the firewall configuration would likely be different; one approach would be to
+add the dedicated network interfaces to the trusted zone.
+======
+
== Allocate a Disk Volume for DRBD ==
DRBD will need its own block device on each node. This can be
a physical disk partition or logical volume, of whatever size
you need for your data. For this document, we will use a
1GiB logical volume, which is more than sufficient for a single HTML file and
(later) GFS2 metadata.
----
[root@pcmk-1 ~]# vgdisplay | grep -e Name -e Free
VG Name fedora-server_pcmk-1
Free PE / Size 511 / 2.00 GiB
[root@pcmk-1 ~]# lvcreate --name drbd-demo --size 1G fedora-server_pcmk-1
Logical volume "drbd-demo" created
[root@pcmk-1 ~]# lvs
LV VG Attr LSize Pool Origin Data% Meta% Move Log Cpy%Sync Convert
drbd-demo fedora-server_pcmk-1 -wi-a----- 1.00g
root fedora-server_pcmk-1 -wi-ao---- 5.00g
swap fedora-server_pcmk-1 -wi-ao---- 1.00g
----
Repeat for the second node, making sure to use the same size:
----
[root@pcmk-1 ~]# ssh pcmk-2 -- lvcreate --name drbd-demo --size 1G fedora-server_pcmk-2
Logical volume "drbd-demo" created
----
== Configure DRBD ==
There is no series of commands for building a DRBD configuration, so simply
run this on both nodes to use this sample configuration:
----
# cat <<END >/etc/drbd.d/wwwdata.res
resource wwwdata {
protocol C;
meta-disk internal;
device /dev/drbd1;
syncer {
verify-alg sha1;
}
net {
allow-two-primaries;
}
on pcmk-1 {
disk /dev/fedora-server_pcmk-1/drbd-demo;
address 192.168.122.101:7789;
}
on pcmk-2 {
disk /dev/fedora-server_pcmk-2/drbd-demo;
address 192.168.122.102:7789;
}
}
END
----
[IMPORTANT]
=========
Edit the file to use the hostnames, IP addresses and logical volume paths
of your nodes if they differ from the ones used in this guide.
=========
[NOTE]
=======
Detailed information on the directives used in this configuration (and
other alternatives) is available at
http://www.drbd.org/users-guide/ch-configure.html
The *allow-two-primaries* option would not normally be used in
an active/passive cluster. We are adding it here for the convenience
of changing to an active/active cluster later.
=======
== Initialize DRBD ==
With the configuration in place, we can now get DRBD running.
These commands create the local metadata for the DRBD resource,
ensure the DRBD kernel module is loaded, and bring up the DRBD resource.
Run them on one node:
----
# drbdadm create-md wwwdata
initializing activity log
NOT initializing bitmap
Writing meta data...
New drbd meta data block successfully created.
# modprobe drbd
# drbdadm up wwwdata
----
We can confirm DRBD's status on this node:
----
# cat /proc/drbd
version: 8.4.5 (api:1/proto:86-101)
srcversion: 153833F4A69E341D3F3E707
1: cs:WFConnection ro:Secondary/Unknown ds:Inconsistent/DUnknown C r----s
ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:1048508
----
Because we have not yet initialized the data, this node's data
is marked as *Inconsistent*. Because we have not yet initialized
the second node, the local state is *WFConnection* (waiting for connection),
and the partner node's status is marked as *Unknown*.
Now, repeat the above commands on the second node. This time,
when we check the status, it shows:
----
# cat /proc/drbd
version: 8.4.5 (api:1/proto:86-101)
srcversion: 153833F4A69E341D3F3E707
1: cs:Connected ro:Secondary/Secondary ds:Inconsistent/Inconsistent C r-----
ns:0 nr:0 dw:0 dr:0 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:1048508
----
You can see the state has changed to *Connected*, meaning the two DRBD nodes
are communicating properly, and both nodes are in *Secondary* role
with *Inconsistent* data.
To make the data consistent, we need to tell DRBD which node should be
considered to have the correct data. In this case, since we are creating
a new resource, both have garbage, so we'll just pick pcmk-1
and run this command on it:
----
[root@pcmk-1 ~]# drbdadm primary --force wwwdata
----
[NOTE]
======
If you are using an older version of DRBD, the required syntax may be different.
See the documentation for your version for how to perform these commands.
======
If we check the status immediately, we'll see something like this:
----
[root@pcmk-1 ~]# cat /proc/drbd
version: 8.4.5 (api:1/proto:86-101)
srcversion: 153833F4A69E341D3F3E707
1: cs:SyncSource ro:Primary/Secondary ds:UpToDate/Inconsistent C r-----
ns:2872 nr:0 dw:0 dr:3784 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:1045636
[>....................] sync'ed: 0.4% (1045636/1048508)K
finish: 0:10:53 speed: 1,436 (1,436) K/sec
----
We can see that this node has the *Primary* role, the partner node has
the *Secondary* role, this node's data is now considered *UpToDate*,
the partner node's data is still *Inconsistent*, and a progress bar
shows how far along the partner node is in synchronizing the data.
After a while, the sync should finish, and you'll see something like:
----
[root@pcmk-1 ~]# cat /proc/drbd
version: 8.4.5 (api:1/proto:86-101)
srcversion: 153833F4A69E341D3F3E707
1: cs:Connected ro:Primary/Secondary ds:UpToDate/UpToDate C r-----
ns:1048508 nr:0 dw:0 dr:1049420 al:0 bm:0 lo:0 pe:0 ua:0 ap:0 ep:1 wo:f oos:0
----
Both sets of data are now *UpToDate*, and we can proceed to creating
and populating a filesystem for our WebSite resource's documents.
== Populate the DRBD Disk ==
On the node with the primary role (pcmk-1 in this example),
create a filesystem on the DRBD device:
----
[root@pcmk-1 ~]# mkfs.xfs /dev/drbd1
meta-data=/dev/drbd1 isize=256 agcount=4, agsize=65532 blks
= sectsz=512 attr=2, projid32bit=1
= crc=0 finobt=0
data = bsize=4096 blocks=262127, imaxpct=25
= sunit=0 swidth=0 blks
naming =version 2 bsize=4096 ascii-ci=0 ftype=0
log =internal log bsize=4096 blocks=853, version=2
= sectsz=512 sunit=0 blks, lazy-count=1
realtime =none extsz=4096 blocks=0, rtextents=0
----
[NOTE]
====
In this example, we create an xfs filesystem with no special options.
In a production environment, you should choose a filesystem type and
options that are suitable for your application.
====
Mount the newly created filesystem, populate it with our web document,
+give it the same SELinux policy as the web document root,
then unmount it (the cluster will handle mounting and unmounting it later):
----
[root@pcmk-1 ~]# mount /dev/drbd1 /mnt
[root@pcmk-1 ~]# cat <<-END >/mnt/index.html
<html>
<body>My Test Site - DRBD</body>
</html>
END
+[root@pcmk-1 ~]# chcon -R --reference=/var/www/html /mnt
[root@pcmk-1 ~]# umount /dev/drbd1
----
== Configure the Cluster for the DRBD device ==
One handy feature `pcs` has is the ability to queue up several changes
into a file and commit those changes atomically. To do this, start by
populating the file with the current raw XML config from the CIB.
----
[root@pcmk-1 ~]# pcs cluster cib drbd_cfg
----
Using the `pcs -f` option, make changes to the configuration saved
in the +drbd_cfg+ file. These changes will not be seen by the cluster until
the +drbd_cfg+ file is pushed into the live cluster's CIB later.
Here, we create a cluster resource for the DRBD device, and an additional _clone_
resource to allow the resource to run on both nodes at the same time.
----
[root@pcmk-1 ~]# pcs -f drbd_cfg resource create WebData ocf:linbit:drbd \
drbd_resource=wwwdata op monitor interval=60s
[root@pcmk-1 ~]# pcs -f drbd_cfg resource master WebDataClone WebData \
master-max=1 master-node-max=1 clone-max=2 clone-node-max=1 \
notify=true
[root@pcmk-1 ~]# pcs -f drbd_cfg resource show
ClusterIP (ocf::heartbeat:IPaddr2): Started
WebSite (ocf::heartbeat:apache): Started
Master/Slave Set: WebDataClone [WebData]
Stopped: [ pcmk-1 pcmk-2 ]
----
After you are satisfied with all the changes, you can commit
them all at once by pushing the drbd_cfg file into the live CIB.
----
[root@pcmk-1 ~]# pcs cluster cib-push drbd_cfg
CIB updated
----
[NOTE]
====
Early versions of `pcs` required `push cib` in place of `cib-push` above.
====
Let's see what the cluster did with the new configuration:
----
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 16:39:43 2014
Last change: Wed Dec 17 16:39:30 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a9c8177
2 Nodes configured
4 Resources configured
Online: [ pcmk-1 pcmk-2 ]
Full list of resources:
ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1
WebSite (ocf::heartbeat:apache): Started pcmk-1
Master/Slave Set: WebDataClone [WebData]
Masters: [ pcmk-1 ]
Slaves: [ pcmk-2 ]
PCSD Status:
pcmk-1: Online
pcmk-2: Online
Daemon Status:
corosync: active/disabled
pacemaker: active/disabled
pcsd: active/enabled
----
We can see that *WebDataClone* (our DRBD device) is running as master (DRBD's
primary role) on *pcmk-1* and slave (DRBD's secondary role) on *pcmk-2*.
[IMPORTANT]
====
The resource agent should load the DRBD module when needed if it's not already
loaded. If that does not happen, configure your operating system to load the
module at boot time. For &DISTRO; &DISTRO_VERSION;, you would run this on both
nodes:
----
# echo drbd >/etc/modules-load.d/drbd.conf
----
====
== Configure the Cluster for the Filesystem ==
Now that we have a working DRBD device, we need to mount its filesystem.
In addition to defining the filesystem, we also need to
tell the cluster where it can be located (only on the DRBD Primary)
and when it is allowed to start (after the Primary was promoted).
We are going to take a shortcut when creating the resource this time.
Instead of explicitly saying we want the *ocf:heartbeat:Filesystem* script, we
are only going to ask for *Filesystem*. We can do this because we know there is only
one resource script named *Filesystem* available to pacemaker, and that pcs is smart
enough to fill in the *ocf:heartbeat:* portion for us correctly in the configuration.
If there were multiple *Filesystem* scripts from different OCF providers, we would need
to specify the exact one we wanted.
Once again, we will queue our changes to a file and then push the
new configuration to the cluster as the final step.
----
[root@pcmk-1 ~]# pcs cluster cib fs_cfg
[root@pcmk-1 ~]# pcs -f fs_cfg resource create WebFS Filesystem \
device="/dev/drbd1" directory="/var/www/html" fstype="xfs"
[root@pcmk-1 ~]# pcs -f fs_cfg constraint colocation add WebFS with WebDataClone INFINITY with-rsc-role=Master
[root@pcmk-1 ~]# pcs -f fs_cfg constraint order promote WebDataClone then start WebFS
Adding WebDataClone WebFS (kind: Mandatory) (Options: first-action=promote then-action=start)
----
We also need to tell the cluster that Apache needs to run on the same
machine as the filesystem and that it must be active before Apache can
start.
----
[root@pcmk-1 ~]# pcs -f fs_cfg constraint colocation add WebSite with WebFS INFINITY
[root@pcmk-1 ~]# pcs -f fs_cfg constraint order WebFS then WebSite
Adding WebFS WebSite (kind: Mandatory) (Options: first-action=start then-action=start)
----
Review the updated configuration.
----
[root@pcmk-1 ~]# pcs -f fs_cfg constraint
Location Constraints:
Ordering Constraints:
start ClusterIP then start WebSite (kind:Mandatory)
promote WebDataClone then start WebFS (kind:Mandatory)
start WebFS then start WebSite (kind:Mandatory)
Colocation Constraints:
WebSite with ClusterIP (score:INFINITY)
WebFS with WebDataClone (score:INFINITY) (with-rsc-role:Master)
WebSite with WebFS (score:INFINITY)
----
----
[root@pcmk-1 ~]# pcs -f fs_cfg resource show
ClusterIP (ocf::heartbeat:IPaddr2): Started
WebSite (ocf::heartbeat:apache): Started
Master/Slave Set: WebDataClone [WebData]
Masters: [ pcmk-1 ]
Slaves: [ pcmk-2 ]
WebFS (ocf::heartbeat:Filesystem): Stopped
----
After reviewing the new configuration, upload it and watch the
cluster put it into effect.
----
[root@pcmk-1 ~]# pcs cluster cib-push fs_cfg
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 17:02:45 2014
Last change: Wed Dec 17 17:02:42 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a9c8177
2 Nodes configured
5 Resources configured
Online: [ pcmk-1 pcmk-2 ]
Full list of resources:
ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-1
WebSite (ocf::heartbeat:apache): Started pcmk-1
Master/Slave Set: WebDataClone [WebData]
Masters: [ pcmk-1 ]
Slaves: [ pcmk-2 ]
WebFS (ocf::heartbeat:Filesystem): Started pcmk-1
PCSD Status:
pcmk-1: Online
pcmk-2: Online
Daemon Status:
corosync: active/disabled
pacemaker: active/disabled
pcsd: active/enabled
----
== Test Cluster Failover ==
Previously, we used `pcs cluster stop pcmk-1` to stop all cluster
services on *pcmk-1*, failing over the cluster resources, but there is another
way to safely simulate node failure.
We can put the node into _standby mode_. Nodes in this state continue to
run corosync and pacemaker but are not allowed to run resources. Any resources
found active there will be moved elsewhere. This feature can be particularly
useful when performing system administration tasks such as updating packages
used by cluster resources.
Put the active node into standby mode, and observe the cluster move all
the resources to the other node. The node's status will
change to indicate that it can no longer host resources.
----
[root@pcmk-1 ~]# pcs cluster standby pcmk-1
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 17:14:05 2014
Last change: Wed Dec 17 17:14:02 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a9c8177
2 Nodes configured
5 Resources configured
Node pcmk-1 (1): standby
Online: [ pcmk-2 ]
Full list of resources:
ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2
WebSite (ocf::heartbeat:apache): Started pcmk-2
Master/Slave Set: WebDataClone [WebData]
Masters: [ pcmk-2 ]
Stopped: [ pcmk-1 ]
WebFS (ocf::heartbeat:Filesystem): Started pcmk-2
PCSD Status:
pcmk-1: Online
pcmk-2: Online
Daemon Status:
corosync: active/disabled
pacemaker: active/disabled
pcsd: active/enabled
----
Once we've done everything we needed to on pcmk-1 (in this case nothing,
we just wanted to see the resources move), we can allow the node to be a
full cluster member again.
----
[root@pcmk-1 ~]# pcs cluster unstandby pcmk-1
[root@pcmk-1 ~]# pcs status
Cluster name: mycluster
Last updated: Wed Dec 17 17:15:36 2014
Last change: Wed Dec 17 17:15:33 2014
Stack: corosync
Current DC: pcmk-2 (2) - partition with quorum
Version: 1.1.12-a9c8177
2 Nodes configured
5 Resources configured
Online: [ pcmk-1 pcmk-2 ]
Full list of resources:
ClusterIP (ocf::heartbeat:IPaddr2): Started pcmk-2
WebSite (ocf::heartbeat:apache): Started pcmk-2
Master/Slave Set: WebDataClone [WebData]
Masters: [ pcmk-2 ]
Slaves: [ pcmk-1 ]
WebFS (ocf::heartbeat:Filesystem): Started pcmk-2
PCSD Status:
pcmk-1: Online
pcmk-2: Online
Daemon Status:
corosync: active/disabled
pacemaker: active/disabled
pcsd: active/enabled
----
Notice that *pcmk-1* is back to the *Online* state, and that the cluster resources
stay where they are due to our resource stickiness settings configured earlier.