NiFi Registry (or other services) failed to install on brand new Node with following error:
<pre><code class="lang-bash">Service did not start successfully; not all of the required roles started: only 0/1 roles started. Reasons : Service has only 0 NiFi Registry roles running instead of minimum required 1.
</code></pre>
Check on <code>/var/run/cloudera-scm-agent/process/1546351536-nifiregistry-NIFI_REGISTRY_SERVER/scripts/logs/stdout.log</code>
<pre><code class="lang-bash">WARN/ERROR: Command 'python' doesn't work, please check environment is configured properly. It could cause NiFi start to fail: /var/run/cloudera-scm-agent/process/1546351536-nifiregistry-NIFI_REGISTRY_SERVER/scripts/common-scripts/basecontrol.sh: line 5: python: command not found
</code></pre>
Check on OS side (RHEL8)
<pre><code class="lang-bash">$ python
python: command not found
</code></pre>
Caused: Since RHEL8 <code>python</code> link is not set by default. User must select which python2 or python3 version they preferred.
<pre><code class="lang-bash">$ alternative --config python
then select python2 binary
</code></pre>

NiFi Registry (or other services) failed to install on brand new Node with following error:

```bash
Service did not start successfully; not all of the required roles started: only 0/1 roles started. Reasons : Service has only 0 NiFi Registry roles running instead of minimum required 1.
```

Check on `/var/run/cloudera-scm-agent/process/1546351536-nifiregistry-NIFI_REGISTRY_SERVER/scripts/logs/stdout.log`

```bash
WARN/ERROR: Command 'python' doesn't work, please check environment is configured properly. It could cause NiFi start to fail: /var/run/cloudera-scm-agent/process/1546351536-nifiregistry-NIFI_REGISTRY_SERVER/scripts/common-scripts/basecontrol.sh: line 5: python: command not found
```

Check on OS side (RHEL8)

```bash
$ python
python: command not found
```

Caused: Since RHEL8 `python` link is not set by default. User must select which python2 or python3 version they preferred.

```bash
$ alternative --config python
then select python2 binary
```

Unable to install NiFi Registry Service on CM