Follow below commands to fix mongodb not starting issue on Ubuntu System and other debian
sudo chown -R mongodb:mongodb /var/log/mongodb
sudo chown -R mongodb:mongodb /var/lib/mongodb
sudo chmod -R 755 /var/lib/mongodb
sudo chmod -R 755 /var/log/mongodb
sudo chown mongodb /tmp/mongodb-27017.sock
sudo chgrp mongodb /tmp/mongodb-27017.sock
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