Developer license can not be registered with NullPointerException and UnknownHostException

Issue

• When deploying a developer license, the DXP instance can not be activated with NullPointerException and UnknownHostException

2023-05-15 05:35:37.524 ERROR [fileinstall-/home/username/liferay-dxp-digital-enterprise-7.0.10-de-98/osgi/modules][LicenseManager:?] DXP Development license validation failed
java.lang.NullPointerException
at java.util.Hashtable.put(Hashtable.java:461)
at com.liferay.portal.license.LicenseManager.f(Unknown Source)
at com.liferay.portal.license.LicenseManager.getServerId(Unknown Source)
at com.liferay.portal.license.LicenseManager.c(Unknown Source)
at com.liferay.portal.license.LicenseManager.checkBinaryLicense(Unknown Source)
at com.liferay.portal.license.LicenseManager.registerLicense(Unknown Source)
at com.liferay.portal.license.util.LocalLicenseManagerImpl.registerLicense(LocalLicenseManagerImpl.java:82)
at com.liferay.portal.kernel.license.util.LicenseManagerUtil.registerLicense(LicenseManagerUtil.java:79)
at com.liferay.portal.license.deployer.internal.installer.LicenseInstaller.install(LicenseInstaller.java:71)
at org.apache.felix.fileinstall.internal.DirectoryWatcher.install(DirectoryWatcher.java:937)
at org.apache.felix.fileinstall.internal.DirectoryWatcher.install(DirectoryWatcher.java:871)
at org.apache.felix.fileinstall.internal.DirectoryWatcher.doProcess(DirectoryWatcher.java:485)
at org.apache.felix.fileinstall.internal.DirectoryWatcher.process(DirectoryWatcher.java:361)
at org.apache.felix.fileinstall.internal.DirectoryWatcher.run(DirectoryWatcher.java:312)
2023-05-15 06:25:06.734 INFO [fileinstall-/home/username/liferay-dxp-digital-enterprise-7.0.10-de-98/osgi/modules][LicenseManager:?] License registered for DXP Development)

2023-05-15 06:24:52.079 ERROR [Start Level: Equinox Container: a0205a0f-e9f2-001d-1733-dbe89e521793][Cache:224] Unable to set localhost. This prevents creation of a GUID. Cause was: hostname: hostname: Name or service not known
java.net.UnknownHostException: hostname: hostname: Name or service not known
at java.net.InetAddress.getLocalHost(InetAddress.java:1512)
at net.sf.ehcache.Cache.<clinit>(Cache.java:222)
at net.sf.ehcache.config.ConfigurationHelper.createCache(ConfigurationHelper.java:305)
at net.sf.ehcache.config.ConfigurationHelper.createDefaultCache(ConfigurationHelper.java:223)
at net.sf.ehcache.CacheManager.configure(CacheManager.java:788)
at net.sf.ehcache.CacheManager.doInit(CacheManager.java:474)
at net.sf.ehcache.CacheManager.init(CacheManager.java:398)
at net.sf.ehcache.CacheManager.<init>(CacheManager.java:269)
at com.liferay.portal.cache.ehcache.internal.EhcachePortalCacheManager.initPortalCacheManager(EhcachePortalCacheManager.java:253)
at com.liferay.portal.cache.BasePortalCacheManager.initialize(BasePortalCacheManager.java:236)
at com.liferay.portal.cache.ehcache.internal.MultiVMEhcachePortalCacheManager.activate(MultiVMEhcachePortalCacheManager.java:70)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
...
Caused by: java.net.UnknownHostException: hostname: Name or service not known
at java.net.Inet4AddressImpl.lookupAllHostAddr(Native Method)
at java.net.InetAddress$2.lookupAllHostAddr(InetAddress.java:929)
at java.net.InetAddress.getAddressesFromNameService(InetAddress.java:1330)
at java.net.InetAddress.getLocalHost(InetAddress.java:1507)
... 238 more

Environment

• Liferay DXP 7.0 

Resolution

• The error is due to the network configuration on the OS level. More specifically, the hostname does not resolve into any known IP address. The OS is unable to get the corresponding IP address. This makes the UnknownHostException to be thrown when getting the localhost. The logic happens in several places, one of them being the license validation code.
• To resolve this, check the /etc/hosts file and make sure that the following line exists:

  127.0.1.1 hostname

  Note: Replace hostname to the real hostname of your OS (output of hostname command).