JMOD(1) JDK Commands JMOD(1)
NAME
jmod - create JMOD files and list the content of existing JMOD files
SYNOPSIS
jmod (create|extract|list|describe|hash) [options] jmod-file
Includes the following:
Main operation modes
create Creates a new JMOD archive file.
extract
Extracts all the files from the JMOD archive file.
list Prints the names of all the entries.
describe
Prints the module details.
hash Determines leaf modules and records the hashes of the
dependencies that directly and indirectly require them.
Options
options
See Options for jmod.
Required
jmod-file
Specifies the name of the JMOD file to create or from which to
retrieve information.
DESCRIPTION
Note: For most development tasks, including deploying modules on the
module path or publishing them to a Maven repository, continue to
package modules in modular JAR files. The jmod tool is intended for
modules that have native libraries or other configuration files or for
modules that you intend to link, with the jlink tool, to a runtime
image.
The JMOD file format lets you aggregate files other than .class files,
metadata, and resources. This format is transportable but not
executable, which means that you can use it during compile time or link
time but not at run time.
Many jmod options involve specifying a path whose contents are copied
into the resulting JMOD files. These options copy all the contents of
the specified path, including subdirectories and their contents, but
exclude files whose names match the pattern specified by the --exclude
option.
With the --hash-modules option or the jmod hash command, you can, in
each module's descriptor, record hashes of the content of the modules
that are allowed to depend upon it, thus "tying" together these
modules. This enables a package to be exported to one or more
specifically-named modules and to no others through qualified exports.
The runtime verifies if the recorded hash of a module matches the one
resolved at run time; if not, the runtime returns an error.
OPTIONS FOR JMOD
--class-path path
Specifies the location of application JAR files or a directory
containing classes to copy into the resulting JMOD file.
--cmds path
Specifies the location of native commands to copy into the
resulting JMOD file.
--compress compress
Specifies the compression to use in creating the JMOD file. The
accepted values are zip-[0-9], where zip-0 provides no
compression, and zip-9 provides the best compression. Default
is zip-6.
--config path
Specifies the location of user-editable configuration files to
copy into the resulting JMOD file.
--dateTIMESTAMP
The timestamp in ISO-8601 extended offset date-time with
optional time-zone format, to use for the timestamp of the
entries, e.g. "2022-02-12T12:30:00-05:00".
--dir path
Specifies the location where jmod puts extracted files from the
specified JMOD archive.
--dry-run
Performs a dry run of hash mode. It identifies leaf modules and
their required modules without recording any hash values.
--exclude pattern-list
Excludes files matching the supplied comma-separated pattern
list, each element using one the following forms:
o glob-pattern
o glob:glob-pattern
o regex:regex-pattern
See the FileSystem.getPathMatcher method for the syntax of
glob-pattern. See the Pattern class for the syntax of
regex-pattern, which represents a regular expression.
--hash-modules regex-pattern
Determines the leaf modules and records the hashes of the
dependencies directly and indirectly requiring them, based on
the module graph of the modules matching the given
regex-pattern. The hashes are recorded in the JMOD archive file
being created, or a JMOD archive or modular JAR on the module
path specified by the jmod hash command.
--header-files path
Specifies the location of header files to copy into the
resulting JMOD file.
--help or -h
Prints a usage message.
--help-extra
Prints help for extra options.
--legal-notices path
Specifies the location of legal notices to copy into the
resulting JMOD file.
--libs path
Specifies location of native libraries to copy into the
resulting JMOD file.
--main-class class-name
Specifies main class to record in the module-info.class file.
--man-pages path
Specifies the location of man pages to copy into the resulting
JMOD file.
--module-version module-version
Specifies the module version to record in the module-info.class
file.
--module-path path or -p path
Specifies the module path. This option is required if you also
specify --hash-modules.
--target-platform platform
Specifies the target platform.
--version
Prints version information of the jmod tool.
@filename
Reads options from the specified file.
An options file is a text file that contains the options and
values that you would ordinarily enter in a command prompt.
Options may appear on one line or on several lines. You may not
specify environment variables for path names. You may comment
out lines by prefixinga hash symbol (#) to the beginning of the
line.
The following is an example of an options file for the jmod
command:
#Wed Dec 07 00:40:19 EST 2016
create --class-path mods/com.greetings --module-path mlib
--cmds commands --config configfiles --header-files src/h
--libs lib --main-class com.greetings.Main
--man-pages man --module-version 1.0
--os-arch "x86_x64" --os-name "macOS"
--os-version "10.10.5" greetingsmod
EXTRA OPTIONS FOR JMOD
In addition to the options described in Options for jmod, the following
are extra options that can be used with the command.
--do-not-resolve-by-default
Exclude from the default root set of modules
--warn-if-resolved
Hint for a tool to issue a warning if the module is resolved.
One of deprecated, deprecated-for-removal, or incubating.
JMOD CREATE EXAMPLE
The following is an example of creating a JMOD file:
jmod create --class-path mods/com.greetings --cmds commands
--config configfiles --header-files src/h --libs lib
--main-class com.greetings.Main --man-pages man --module-version 1.0
--os-arch "x86_x64" --os-name "macOS"
--os-version "10.10.5" greetingsmod
Create a JMOD file specifying the date for the entries as 2022 March 15
00:00:00:
jmod create --class-path build/foo/classes --date 2022-03-15T00:00:00Z
jmods/foo1.jmod
JMOD HASH EXAMPLE
The following example demonstrates what happens when you try to link a
leaf module (in this example, ma) with a required module (mb), and the
hash value recorded in the required module doesn't match that of the
leaf module.
1. Create and compile the following .java files:
o jmodhashex/src/ma/module-info.java
module ma {
requires mb;
}
o jmodhashex/src/mb/module-info.java
module mb {
}
o jmodhashex2/src/ma/module-info.java
module ma {
requires mb;
}
o jmodhashex2/src/mb/module-info.java
module mb {
}
2. Create a JMOD archive for each module. Create the directories
jmodhashex/jmods and jmodhashex2/jmods, and then run the following
commands from the jmodhashex directory, then from the jmodhashex2
directory:
o jmod create --class-path mods/ma jmods/ma.jmod
o jmod create --class-path mods/mb jmods/mb.jmod
3. Optionally preview the jmod hash command. Run the following command
from the jmodhashex directory:
jmod hash --dry-run -module-path jmods --hash-modules .*
The command prints the following:
Dry run:
mb
hashes ma SHA-256 07667d5032004b37b42ec2bb81b46df380cf29e66962a16481ace2e71e74073a
This indicates that the jmod hash command (without the --dry-run
option) will record the hash value of the leaf module ma in the
module mb.
4. Record hash values in the JMOD archive files contained in the
jmodhashex directory. Run the following command from the jmodhashex
directory:
jmod hash --module-path jmods --hash-modules .*
The command prints the following:
Hashes are recorded in module mb
5. Print information about each JMOD archive contained in the
jmodhashex directory. Run the highlighted commands from the
jmodhashex directory:
jmod describe jmods/ma.jmod
ma
requires mandated java.base
requires mb
jmod describe jmods/mb.jmod
mb
requires mandated java.base
hashes ma SHA-256 07667d5032004b37b42ec2bb81b46df380cf29e66962a16481ace2e71e74073a
6. Attempt to create a runtime image that contains the module ma from
the directory jmodhashex2 but the module mb from the directory
jmodhashex. Run the following command from the jmodhashex2
directory:
o Linux and macOS:
jlink --module-path
$JAVA_HOME/jmods:jmods/ma.jmod:../jmodhashex/jmods/mb.jmod
--add-modules ma --output ma-app
o Windows:
jlink --module-path
%JAVA_HOME%/jmods;jmods/ma.jmod;../jmodhashex/jmods/mb.jmod
--add-modules ma --output ma-app
The command prints an error message similar to the following:
Error: Hash of ma (a2d77889b0cb067df02a3abc39b01ac1151966157a68dc4241562c60499150d2) differs to
expected hash (07667d5032004b37b42ec2bb81b46df380cf29e66962a16481ace2e71e74073a) recorded in mb
JDK 24.0.1 2025 JMOD(1)