Ambari-Update failed (Ambari 2.4 to 2.6) - Hadoop services won't start anymore - hadoop

Question

I just worked through this Upgrade guide for the Hortonworks Data Platform:
https://docs.hortonworks.com/HDPDocuments/Ambari-2.6.0.0/bk_ambari-upgrade/bk_ambari-upgrade.pdf
I did all the steps as described in section 1 - 4 (Ambari upgrade). But now I have the problem, that my services won't start anymore!
Ambari can find all hosts, but they won't start!
E.g. for the HDFS starting I got the following error message:
2017-11-13 19:41:11,427 - Unable to load available packages
Traceback (most recent call last):
File "/usr/lib/python2.6/site-packages/resource_management/libraries/script/script.py", line 771, in load_available_packages
self.available_packages_in_repos = pkg_provider.get_available_packages_in_repos(repos)
File "/usr/lib/python2.6/site-packages/resource_management/core/providers/package/yumrpm.py", line 85, in get_available_packages_in_repos
available_packages.extend(self._get_available_packages(repo))
File "/usr/lib/python2.6/site-packages/resource_management/core/providers/package/yumrpm.py", line 146, in _get_available_packages
return self._lookup_packages(cmd, 'Available Packages')
File "/usr/lib/python2.6/site-packages/resource_management/core/providers/package/yumrpm.py", line 191, in _lookup_packages
if items[i + 2].find('#') == 0:
IndexError: list index out of range
Traceback (most recent call last):
File "/var/lib/ambari-agent/cache/common-services/HDFS/2.1.0.2.0/package/scripts/hdfs_client.py", line 73, in <module>
HdfsClient().execute()
File "/usr/lib/python2.6/site-packages/resource_management/libraries/script/script.py", line 367, in execute
method(env)
File "/usr/lib/python2.6/site-packages/resource_management/libraries/script/script.py", line 930, in restart
self.install(env)
File "/var/lib/ambari-agent/cache/common-services/HDFS/2.1.0.2.0/package/scripts/hdfs_client.py", line 35, in install
import params
File "/var/lib/ambari-agent/cache/common-services/HDFS/2.1.0.2.0/package/scripts/params.py", line 25, in <module>
from params_linux import *
File "/var/lib/ambari-agent/cache/common-services/HDFS/2.1.0.2.0/package/scripts/params_linux.py", line 391, in <module>
lzo_packages = get_lzo_packages(stack_version_unformatted)
File "/usr/lib/python2.6/site-packages/resource_management/libraries/functions/get_lzo_packages.py", line 45, in get_lzo_packages
lzo_packages += [script_instance.format_package_name("hadooplzo_${stack_version}"),
File "/usr/lib/python2.6/site-packages/resource_management/libraries/script/script.py", line 538, in format_package_name
raise Fail("Cannot match package for regexp name {0}. Available packages: {1}".format(name, self.available_packages_in_repos))
resource_management.core.exceptions.Fail: Cannot match package for regexp name hadooplzo_${stack_version}. Available packages: []
(I think the most important part is the message resource_management.core.exceptions.Fail: Cannot match package for regexp name hadooplzo_${stack_version}. Available packages: [] which looks like there would be no version (package) available...!
I just saw, that I upgraded also the Ambari Metrics Monitor, Ambari Metrics Hadoop Sink and the Metrics Collector before starting the Services once (the manual is a little bit confusing here, see step 4.3.3)! Was this a mistake?
I tried to upgrade from Ambari 2.4 to Ambari 2.6 (HDP 2.5 installed)! Operating system is CentOS 7.
However, I need to reset / downgrade the Ambari or upgrade the Services to be able to start them again! Can someone help? Any help would be appreciated! Thank you!

Answer 1

Finally I was able to downgrade my Ambari installation back to version 2.4.2 as it was before starting the upgrade process.
To make a downgrade you have to do the following steps on the appropriate nodes:
# delete the new ambari repo file
rm /etc/yum.repos.d/ambari.repo
# download the old ambari repo file (for me version 2.4.2), as described in ambari installation guide (here for Centos 7)
wget -nv http://public-repo-1.hortonworks.com/ambari/centos7/2.x/updates/2.4.2.0/ambari.repo -O /etc/yum.repos.d/ambari.repo
yum clean all
yum repolist
# check for the correct version (e.g. 2.4.2) of the Ambari repo
# Downgrade all components to this version
yum downgrade ambari-metrics-monitor
yum downgrade ambari-metrics-hadoop-sink
yum downgrade ambari-agent
...
Afterwards I upgraded again, but to Ambari version 2.5.2.0, which now worked without a problem. I also was able to upgrade my HDP installation to version 2.6.3.0 via this Ambari version.
I will skip Ambari 2.6.0 and will try to upgrade Ambari with a later future release.