In addition to running Spring Boot applications by using java -jar
, it is also
possible to make fully executable applications for Unix systems. A fully executable jar
can be executed like any other executable binary or it can be
registered with init.d
or systemd
. This makes it very easy to
install and manage Spring Boot applications in common production environments.
Caution | |
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Fully executable jars work by embedding an extra script at the front of the file.
Currently, some tools do not accept this format, so you may not always be able to use this
technique. For example, |
To create a ‘fully executable’ jar with Maven, use the following plugin configuration:
<plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> <configuration> <executable>true</executable> </configuration> </plugin>
The following example shows the equivalent Gradle configuration:
bootJar { launchScript() }
You can then run your application by typing ./my-application.jar
(where my-application
is the name of your artifact). The directory containing the jar is used as your
application’s working directory.
The default script supports most Linux distributions and is tested on CentOS and Ubuntu.
Other platforms, such as OS X and FreeBSD, require the use of a custom
embeddedLaunchScript
.
Spring Boot application can be easily started as Unix/Linux services by using either
init.d
or systemd
.
If you configured Spring Boot’s Maven or Gradle plugin to generate a fully executable jar, and you do not use a custom embeddedLaunchScript
, your
application can be used as an init.d
service. To do so, symlink the jar to init.d
to
support the standard start
, stop
, restart
, and status
commands.
The script supports the following features:
/var/run/<appname>/<appname>.pid
/var/log/<appname>.log
Assuming that you have a Spring Boot application installed in /var/myapp
, to install a
Spring Boot application as an init.d
service, create a symlink, as follows:
$ sudo ln -s /var/myapp/myapp.jar /etc/init.d/myapp
Once installed, you can start and stop the service in the usual way. For example, on a Debian-based system, you could start it with the following command:
$ service myapp start
Tip | |
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If your application fails to start, check the log file written to
|
You can also flag the application to start automatically by using your standard operating system tools. For example, on Debian, you could use the following command:
$ update-rc.d myapp defaults <priority>
Note | |
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The following is a set of guidelines on how to secure a Spring Boot application that runs as an init.d service. It is not intended to be an exhaustive list of everything that should be done to harden an application and the environment in which it runs. |
When executed as root, as is the case when root is being used to start an init.d service,
the default executable script runs the application as the user who owns the jar file. You
should never run a Spring Boot application as root
, so your application’s jar file
should never be owned by root. Instead, create a specific user to run your application and
use chown
to make it the owner of the jar file, as shown in the following example:
$ chown bootapp:bootapp your-app.jar
In this case, the default executable script runs the application as the bootapp
user.
Tip | |
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To reduce the chances of the application’s user account being compromised, you should
consider preventing it from using a login shell. For example, you can set the account’s
shell to |
You should also take steps to prevent the modification of your application’s jar file. Firstly, configure its permissions so that it cannot be written and can only be read or executed by its owner, as shown in the following example:
$ chmod 500 your-app.jar
Second, you should also take steps to limit the damage if your application or the account
that’s running it is compromised. If an attacker does gain access, they could make the jar
file writable and change its contents. One way to protect against this is to make it
immutable by using chattr
, as shown in the following example:
$ sudo chattr +i your-app.jar
This will prevent any user, including root, from modifying the jar.
If root is used to control the application’s service and you
use a .conf
file to customize its
startup, the .conf
file is read and evaluated by the root user. It should be secured
accordingly. Use chmod
so that the file can only be read by the owner and use chown
to
make root the owner, as shown in the following example:
$ chmod 400 your-app.conf $ sudo chown root:root your-app.conf
systemd
is the successor of the System V init system and is now being used by many
modern Linux distributions. Although you can continue to use init.d
scripts with
systemd
, it is also possible to launch Spring Boot applications by using systemd
‘service’ scripts.
Assuming that you have a Spring Boot application installed in /var/myapp
, to install a
Spring Boot application as a systemd
service, create a script named myapp.service
and
place it in /etc/systemd/system
directory. The following script offers an example:
[Unit] Description=myapp After=syslog.target [Service] User=myapp ExecStart=/var/myapp/myapp.jar SuccessExitStatus=143 [Install] WantedBy=multi-user.target
Important | |
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Remember to change the |
Note | |
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The |
Note that, unlike when running as an init.d
service, the user that runs the application,
the PID file, and the console log file are managed by systemd
itself and therefore must
be configured by using appropriate fields in the ‘service’ script. Consult the
service unit
configuration man page for more details.
To flag the application to start automatically on system boot, use the following command:
$ systemctl enable myapp.service
Refer to man systemctl
for more details.
The default embedded startup script written by the Maven or Gradle plugin can be
customized in a number of ways. For most people, using the default script along with a few
customizations is usually enough. If you find you cannot customize something that you need
to, use the embeddedLaunchScript
option to write your own file entirely.
It often makes sense to customize elements of the start script as it is written into the jar file. For example, init.d scripts can provide a “description”. Since you know the description up front (and it need not change), you may as well provide it when the jar is generated.
To customize written elements, use the embeddedLaunchScriptProperties
option of the
Spring Boot Maven plugin or the
properties
property of the Spring Boot Gradle plugin’s launchScript
.
The following property substitutions are supported with the default script:
Name | Description | Gradle default | Maven default |
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| The script mode. |
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| The |
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| Single-line version of |
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| The default value for | Folder containing the jar | Folder containing the jar |
| Reference to a file script that should be inlined in the default launch script.
This can be used to set environmental variables such as | ||
| Default value for | ||
| Default value for | ||
| Default value for | ||
| Default value for the name of the PID file in | ||
| Whether the |
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| Default value for | 60 | 60 |
For items of the script that need to be customized after the jar has been written, you can use environment variables or a config file.
The following environment properties are supported with the default script:
Variable | Description |
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| The “mode” of operation. The default depends on the way the jar was built but is
usually |
| Whether the |
| The root name of the pid folder ( |
| The name of the folder in which to put log files ( |
| The name of the folder from which to read .conf files (same folder as jar-file by default). |
| The name of the log file in the |
| The name of the app. If the jar is run from a symlink, the script guesses the app name. If it is not a symlink or you want to explicitly set the app name, this can be useful. |
| The arguments to pass to the program (the Spring Boot app). |
| The location of the |
| Options that are passed to the JVM when it is launched. |
| The explicit location of the jar file, in case the script is being used to launch a jar that it is not actually embedded. |
| If not empty, sets the |
| The time in seconds to wait when stopping the application before forcing a shutdown ( |
Note | |
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The |
With the exception of JARFILE
and APP_NAME
, the settings listed in the preceding
section can be configured by using a .conf
file. The file is expected to be next to the
jar file and have the same name but suffixed with .conf
rather than .jar
. For example,
a jar named /var/myapp/myapp.jar
uses the configuration file named
/var/myapp/myapp.conf
, as shown in the following example:
myapp.conf.
JAVA_OPTS=-Xmx1024M LOG_FOLDER=/custom/log/folder
Tip | |
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If you do not like having the config file next to the jar file, you can set a
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To learn about securing this file appropriately, see the guidelines for securing an init.d service.
A Spring Boot application can be started as a Windows service by using
winsw
.
A (separately maintained sample) describes step-by-step how you can create a Windows service for your Spring Boot application.