Exception:

The username you provided is not allowed to use the text-based Tomcat Manager (error 403)

Solution:

Configure tomcat to allow deployment from other source

$ sudo nano ./apache-tomcat-8.5.46/webapps/manager/META-INF/context.xml
<!-- <Valve className="org.apache.catalina.valves.RemoteAddrValve"
allow="127\.\d+\.\d+\.\d+|::1|0:0:0:0:0:0:0:1" /> -->
$ ./apache-tomcat-8.5.46/bin/shutdown.sh
$ ./apache-tomcat-8.5.46/bin/startup.sh

Exception:

Job for jenkins.service failed because the control process exited with error code.
See "systemctl status jenkins.service" and "journalctl -xe" for details.
invoke-rc.d: initscript jenkins, action "start" failed.
● jenkins.service - LSB: Start Jenkins at boot time
Loaded: loaded (/etc/init.d/jenkins; generated)
Active: failed (Result: exit-code) since Thu 2019-09-26 14:35:12 UTC; 13ms ago
Docs: man:systemd-sysv-generator(8)
Process: 14063 ExecStart=/etc/init.d/jenkins start (code=exited, status=1/FAILURE)
Sep 26 14:35:12 ip-172-31-45-94 systemd[1]: Starting LSB: Start Jenkins at boot time...
Sep 26 14:35:12 ip-172-31-45-94 jenkins[14063]: ERROR: No Java executable found in current PATH: /bin:/usr/bin:/sbin:/usr/sbin
Sep 26 14:35:12 ip-172-31-45-94 jenkins[14063]: If you actually have java installed on the system make sure the executable is in the aforementioned path and that 'type -p java' returns the java executable path
Sep 26 14:35:12 ip-172-31-45-94 systemd[1]: jenkins.service: Control process exited, code=exited status=1
Sep 26 14:35:12 ip-172-31-45-94 systemd[1]: jenkins.service: Failed with result 'exit-code'.
Sep 26 14:35:12 ip-172-31-45-94 systemd[1]: Failed to start LSB: Start Jenkins at boot time.
dpkg: error processing package jenkins (--configure):
installed jenkins package post-installation script subprocess returned error exit status 1
Processing triggers for ureadahead (0.100.0-21) ...
Processing triggers for systemd (237-3ubuntu10.24) ...
Errors were encountered while processing:
jenkins
E: Sub-process /usr/bin/dpkg returned an error code (1)

Solution:

Update JAVA path for Jenkins

ubuntu@ip-172-31-45-94:~/bin$ sudo nano /etc/init.d/jenkins
PATH=/bin:/usr/bin:/sbin:/usr/sbin:/home/ubuntu/bin/jdk1.8.0_221/bin

ubuntu@ip-172-31-45-94:~/bin$ sudo systemctl daemon-reload
ubuntu@ip-172-31-45-94:~/bin$ sudo service jenkins start
ubuntu@ip-172-31-45-94:~/bin$ sudo service jenkins status
jenkins.service - LSB: Start Jenkins at boot time
Loaded: loaded (/etc/init.d/jenkins; generated)
Active: active (exited) since Thu 2019-09-26 14:42:40 UTC; 1min 53s ago
Docs: man:systemd-sysv-generator(8)
Process: 14221 ExecStart=/etc/init.d/jenkins start (code=exited, status=0/SUCCESS)
Sep 26 14:42:39 ip-172-31-45-94 systemd[1]: Starting LSB: Start Jenkins at boot time...
Sep 26 14:42:39 ip-172-31-45-94 jenkins[14221]: Correct java version found
Sep 26 14:42:39 ip-172-31-45-94 jenkins[14221]: * Starting Jenkins Automation Server jenkins
Sep 26 14:42:39 ip-172-31-45-94 su[14267]: Successful su for jenkins by root
Sep 26 14:42:39 ip-172-31-45-94 su[14267]: + ??? root:jenkins
Sep 26 14:42:39 ip-172-31-45-94 su[14267]: pam_unix(su:session): session opened for user jenkins by (uid=0)
Sep 26 14:42:39 ip-172-31-45-94 su[14267]: pam_unix(su:session): session closed for user jenkins
Sep 26 14:42:40 ip-172-31-45-94 jenkins[14221]: ...done.
Sep 26 14:42:40 ip-172-31-45-94 systemd[1]: Started LSB: Start Jenkins at boot time.