java.io.FileNotFoundException: Domain directory '/u01/oracle11g/mw1036/user_projects/domains/poc_domain' invalid (domain salt file not found)

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Applies to:
Weblogic Server: 10.3.6 and later
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Problem Summary:
Case 1: When we are trying to start managed server through the node manager facing java.io.FileNotFoundException: Domain directory '/u01/oracle11g/mw1036/user_projects/domains/poc_domain' invalid (domain salt file not found) error.

WebLogic server is complaining about a domain that is not correctly registered and enrolled for node Manager.

<Mar 2, 2016 3:16:43 AM CST> <WARNING> <There was a problem initializing the domain 'poc_domain' at '/u01/oracle11g/mw1036/user_projects/domains/poc_domain'. Please make sure that this domainName: 'poc_domain' is registered and is fully enrolled for this NodeManager at: '/u01/oracle11g/mw1036/user_projects/domains/poc_domain'.>

Case 2: Node Manager Status is Inactive on weblogic admin console,
Problem description:weblogic.nodemanager.NMException
Change: Node manager config was copied from box A to B of same domain, changed ListenAddress, Port and started nodemanager.

Error:
<Mar 2, 2016 3:16:43 AM CST> <WARNING> <I/O error while reading domain directory>
java.io.FileNotFoundException: Domain directory '/u01/oracle11g/mw1036/user_projects/domains/poc_domain' invalid (domain salt file not found)
        at weblogic.nodemanager.server.DomainManager.initialize(DomainManager.java:95)
        at weblogic.nodemanager.server.DomainManager.<init>(DomainManager.java:60)
        at weblogic.nodemanager.server.NMServer.findOrCreateDomainManager(NMServer.java:332)
        at weblogic.nodemanager.server.NMServer.getDomainManager(NMServer.java:316)
        at weblogic.nodemanager.server.Handler.handleDomain(Handler.java:277)
        at weblogic.nodemanager.server.Handler.handleCommand(Handler.java:131)
        at weblogic.nodemanager.server.Handler.run(Handler.java:81)
        at java.lang.Thread.run(Thread.java:724)

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Root Cause:
Case 1: Domain root directory(nodemanager.properties) was pointing to wrong directory.
Node manager was referring to wrong domain directory and looking for a SerializedSystemIni.dat file to decrypt the credentials required to start the server causing the exception.

Case 2: Domain isn't registered with node manager.
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Resolution:
Case1:
1. Go to your nodemanager home,
$WL_HOME/common/nodemanager/
2. Edit nodemanager.domains file and make sure it has valid domain root directory.
3. Save your changes.
4. Restart Node Manager
5. Restart Server using Node manager.

Case2:
1. Enroll your nodemanager using NMEnroll command,
nmEnroll('$DOMAIN_HOME','$WL_HOME/common/nodemanager/')
2. Restart your node manager.
3. Check NM status on console.