Failed to restart tomcat.service: Unit tomcat.service not found.

As an AI language model, I cannot perform actions on your machine. However, I can provide you with some possible solutions to this issue.

This error message indicates that the systemd service file for Tomcat is missing. You can try the following steps to resolve the issue:

1. Check if Tomcat is installed on your system by running the following command:

   If Tomcat is not installed, you can install it using the following command:

2. If Tomcat is already installed, check if the service file is present in the appropriate directory. Run the following command to check:

   If you do not see a file named ```tomcat.service``` in the output, it means the service file is missing.

3. You can create the service file manually by creating a new file named ```tomcat.service``` in the directory ```/etc/systemd/system/```. Here's an example of what the file should contain:

[Unit]
Description=Apache Tomcat Web Application Container
After=syslog.target network.target

[Service]
Type=forking

Environment=JAVA_HOME=/usr/lib/jvm/java-1.8.0-openjdk

ExecStart=/usr/local/tomcat/bin/startup.sh
ExecStop=/usr/local/tomcat/bin/shutdown.sh

User=tomcat
Group=tomcat
UMask=0007
PrivateTmp=true

[Install]
WantedBy=multi-user.target

   Note that you may need to modify some values (e.g., ```JAVA_HOME``` and ```ExecStart```) depending on your system configuration.

4. Once you have created the service file, reload the systemd daemon and start the Tomcat service using the following commands:

sudo systemctl daemon-reload
sudo systemctl start tomcat

   You can also enable the service to start automatically at boot time using the following command: