How to find Oracle Java installations on Linux, macOS and Windows

Before you can say which of your Java installs fall under which Oracle license, you need the list. This guide gives copy-paste commands for Linux, macOS and Windows, then shows how to tell an Oracle JDK build from an OpenJDK build without guessing. Everything here is read-only.

Linux

Step 1: list every Java home

Start with the package manager, then look at the file system, because tarball installs never show up in rpm or dpkg. Oracle's own RPM and DEB packages install to /usr/lib/jvm/jdk-<version>-oracle-<arch>, and the RPM adds a /usr/java/jdk-21 symlink.¹

# 1. Packages (names, versions, vendors)
$ rpm -qa --qf '%{NAME} %{VERSION}-%{RELEASE} %{VENDOR}\n' | grep -i -E 'jdk|jre|java'
$ dpkg-query -W -f='${Package} ${Version} ${Maintainer}\n' | grep -i -E 'jdk|jre|java'
# 2. Registered alternatives
$ update-alternatives --list java 2>/dev/null || alternatives --display java
# 3. Every bin/java on local file systems
$ sudo find / -xdev -type f -path '*/bin/java' 2>/dev/null
# 4. What is running right now
$ for p in $(pgrep -x java); do sudo readlink -f /proc/$p/exe; done | sort -u

-xdev keeps find on the root file system; repeat it for other local mounts such as /opt or /srv if they are separate. Also look in each user's ~/.sdkman/candidates/java, ~/.asdf/installs/java, ~/.jdks (IntelliJ IDEA) and ~/.gradle/jdks.

Step 2: read the release file and ask the JVM

Every modern JDK has a plain-text release file in its home directory. JEP 322 defines keys such as JAVA_VERSION and JAVA_VERSION_DATE.⁴ Pair it with the runtime name the JVM reports.

$ for home in /usr/lib/jvm/* /usr/java/* /opt/*; do
    [ -f "$home/release" ] || continue
    echo "== $home"
    grep -E '^(JAVA_VERSION|JAVA_RUNTIME_VERSION|IMPLEMENTOR|BUILD_TYPE)=' "$home/release"
    "$home/bin/java" -XshowSettings:properties -version 2>&1 | grep -E 'java\.runtime\.name|java\.vendor ='
  done

Oracle's JDK 11 release notes explain the naming difference: Oracle JDK says java and includes the LTS identifier, while OpenJDK builds produced by Oracle say OpenJDK.⁵ OpenJDK's default build branding is OpenJDK Runtime Environment with no company name,⁶ so a non-Oracle vendor string plus that runtime name is an OpenJDK build.

macOS

Oracle's macOS installer puts the JDK in /Library/Java/JavaVirtualMachines/jdk-<feature>.jdk, and /usr/libexec/java_home lists what the system knows about.² The older Oracle Java 8 JRE lives in the browser plug-in folder and installs a LaunchAgent for Java Update.

$ /usr/libexec/java_home -V 2>&1
$ ls -d /Library/Java/JavaVirtualMachines/* ~/Library/Java/JavaVirtualMachines/* 2>/dev/null
$ for home in /Library/Java/JavaVirtualMachines/*/Contents/Home; do echo "== $home"; grep -E '^(JAVA_VERSION|IMPLEMENTOR|BUILD_TYPE)=' "$home/release"; done
# Oracle Java 8 JRE (browser plug-in location) and its updater
$ ls -d '/Library/Internet Plug-Ins/JavaAppletPlugin.plugin' /Library/LaunchAgents/com.oracle.java.Java-Updater.plist 2>/dev/null
$ brew list --cask 2>/dev/null | grep -i -E 'jdk|temurin|zulu|corretto|liberica'

Don't remove anything from /usr/bin: Oracle's guide warns that those tools are part of macOS and come back with system updates.²

Windows

Oracle's Windows installer defaults to C:\Program Files\Java\jdk-21 and registers an uninstall entry you can find in the registry.³ Run these in 64-bit PowerShell; a 32-bit session sees a different registry view.

# Java homes registered by installers (64-bit and 32-bit views)
PS> Get-ChildItem 'HKLM:\SOFTWARE\JavaSoft', 'HKLM:\SOFTWARE\WOW6432Node\JavaSoft' -Recurse -ErrorAction SilentlyContinue | Get-ItemProperty | Where-Object JavaHome | Select-Object PSChildName, JavaHome
# Installed programs with a Java, JDK or JRE name
PS> Get-ItemProperty 'HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\*', 'HKLM:\SOFTWARE\WOW6432Node\Microsoft\Windows\CurrentVersion\Uninstall\*' -ErrorAction SilentlyContinue | Where-Object DisplayName -Match 'Java|JDK|JRE' | Select-Object DisplayName, DisplayVersion, Publisher, InstallLocation
# release file of every folder under Program Files\Java
PS> Get-ChildItem 'C:\Program Files\Java', 'C:\Program Files (x86)\Java' -Directory -ErrorAction SilentlyContinue | ForEach-Object { $r = Join-Path $_.FullName 'release'; if (Test-Path $r) { "== $($_.FullName)"; (Select-String -Path $r -Pattern '^(JAVA_VERSION|IMPLEMENTOR|BUILD_TYPE)=').Line } }
# java.exe on PATH, running Java processes, and the Java Update Scheduler
PS> where.exe java
PS> Get-Process java, javaw, jusched -ErrorAction SilentlyContinue | Select-Object Name, Path -Unique

If jusched is running, the Java Update Scheduler is active. Java Update periodically checks for new versions and asks to install them,⁷ and every Oracle Java 8 update since 8u211 is under the OTN license.⁸ On a business machine, clicking Update installs a build that needs a subscription for commercial use.

Containers, images and CI

Host scans miss the Java inside images and pipelines. Search your repositories for Oracle's registry and download URLs, and check running containers directly. The Oracle container registry's java/jdk repository carries images for every JDK release, so a floating tag follows the newest update of that line.⁹

$ grep -rn -E 'container-registry\.oracle\.com/java|download\.oracle\.com/java' --include='Dockerfile*' --include='*.yml' --include='*.yaml' --include='*.sh' .
$ docker ps --format '{{.ID}} {{.Image}}' | while read -r id image; do echo "== $image"; docker exec "$id" java -version 2>&1 | head -2; done

For GitHub Actions, look for distribution: oracle in workflow files; the setup-java guide covers what each version setting downloads.

Reading the results

Doing this on more than a handful of hosts

Loop over hosts with SSH or your configuration management tool and collect structured output, not screenshots of terminal text. Keep one file per host with the hostname, the date, each Java home's path, the release keys and the runtime name. That file is the evidence you will want if anyone asks later how the inventory was produced.

How RuntimeClear helps

The free RuntimeClear scanner runs these same checks on Linux, macOS and Windows, including SDK managers, IDE JDKs, running processes and, with --repo, Dockerfiles and CI files. It is read-only, makes no network calls and writes one JSON file per host. Drop the files into the report tool to see counts by status for free; the paid report adds each finding with its license and the commands to replace it.