Configuring the master host as a ZooKeeper node

This procedure configures the Control Center master host as a node in a ZooKeeper ensemble.

Set the ZooKeeper node ID to 1.

echo "SERVICED_ISVCS_ZOOKEEPER_ID=1" >> /etc/default/serviced

Specify the nodes in the ZooKeeper ensemble.
You can copy the following text and paste it in your console:
```
echo "SERVICED_ZK=${node1}:2181,${node2}:2181,${node3}:2181" \
  >> /etc/default/serviced
```
Specify the nodes in the ZooKeeper quorum.
ZooKeeper requires a unique quorum definition for each node in its ensemble. To achieve this, replace the IP address or hostname of the master host with 0.0.0.0.
You can copy the following text and paste it in your console:
```
q1="1@0.0.0.0:2888:3888"
q2="2@${node2}:2888:3888"
q3="3@${node3}:2888:3888"
echo "SERVICED_ISVCS_ZOOKEEPER_QUORUM=${q1},${q2},${q3}" \
  >> /etc/default/serviced
```
Specify the timeout for inactive connections.
You can copy the following text and paste it in your console:
```
echo "SERVICED_ZK_SESSION_TIMEOUT=15" >> /etc/default/serviced
```
Verify the ZooKeeper environment variables.
```
grep -E '^\b*SERVICED' /etc/default/serviced | grep -E '_Z(OO|K)'
```
The following example shows the environment variables for a master host with IP address 198.51.100.135.
Note: The value of the SERVICED_ISVCS_ZOOKEEPER_QUORUM variable is formatted to fit the available space. The result of the grep command shows the variable and value on the same line.
```
SERVICED_ZK=198.51.100.135:2181,198.51.100.136:2181,198.51.100.137:2181
SERVICED_ISVCS_ZOOKEEPER_ID=1
SERVICED_ISVCS_ZOOKEEPER_QUORUM=1@0.0.0.0:2888:3888,\
  2@198.51.100.136:2888:3888,3@198.51.100.137:2888:3888
SERVICED_ZK_SESSION_TIMEOUT=15
```