Linux where is jdk

Where can I find the Java SDK in Linux after installing it?

I installed JDK using apt-get install but I don’t know where my jdk folder is. I need to set the path for that. Does any one have a clue on the location?

14 Answers 14

This depends a bit from your package system . if the java command works, you can type readlink -f $(which java) to find the location of the java command. On the OpenSUSE system I’m on now it returns /usr/lib64/jvm/java-1.6.0-openjdk-1.6.0/jre/bin/java (but this is not a system which uses apt-get ).

On Ubuntu, it looks like it is in /usr/lib/jvm/java-6-openjdk/ for OpenJDK, and in some other subdirectory of /usr/lib/jvm/ for Suns JDK (and other implementations as well, I think).

For any given package you can determine what files it installs and where it installs them by querying dpkg. For example for the package ‘openjdk-6-jdk’: dpkg -L openjdk-6-jdk

I think readlink as given is most elegant (and efficient), but I suggest readlink -f $(which javac) — note the ‘c’ in case there is a strange mix of JDK and JRE on the same machine. The JDK includes a compiler (javac) and a JRE does not. However if path is not correct, which will fail and you can try this: find /usr/java -wholename ‘*ava/jdk*’ -prune as I note in a comment below.

will tell you which java implementation is the default for your system and where in the filesystem it is installed. Check the manual for more options.

@dequis, it’s an answer specific to debian, since the question mentioned apt-get and the distro to be Debian 2.6.26 . AFAIK, it should be the same for all debian derivatives.

should give you something like

This does not actually point to a full JDK. 1. It is a symlink, and even if you read the symlink, the binary is also not within a JDK. For example, if I run the command readlink -f $(which javac) it prints /usr/lib/jvm/java-8-oracle/bin/javac . That bin folder is NOT a JDK. General acid-base test to see if its a JDK is to see if the current $JAVA_HOME contains a path of lib/tools.jar . In the cast of /usr/lib/jvm/java-8-oracle/bin that is not true, therefore it is not a JDK.

On Centos / RHL This is what I prefer to find the JDK (if installed) find /usr/java -wholename ‘*ava/jdk*’ -prune But behavior depends whether you are talking about OpenJDK or Oracle Java and how it was installed in the first place.

This question will get moved but you can do the following

«find / -name ‘javac'» is less typing, but requires admin (root) privilege or you will get a lot permission denied messages.

Use find to located it. It should be under /usr somewhere:

When running the command, if there are too many «Permission denied» message obfuscating the actual found results then, simply redirect stderr to /dev/null

find /usr -name java 2> /dev/null 

Another best way to find Java folder path is to use alternatives command in Fedora Linux (I know its for Ubuntu but I hit this post from google just by its headline). Just want to share incase people like me looking for answers for fedora flavour.

To display all information regarding java

alternatives --display java 

Three Step Process: First: open Terminal-> $ whereis java it would give output like this: java: /usr/bin/java /usr/share/java /usr/share/man/man1/java.1.gz

Second: ls -l /usr/bin/java It would give output like this: lrwxrwxrwx 1 root root 22 Feb 9 10:59 /usr/bin/java -> /etc/alternatives/java

Third: ls -l /etc/alternatives/java output is the JDK path: lrwxrwxrwx 1 root root 46 Feb 9 10:59 /etc/alternatives/java -> /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java

It’s /usr/local/java/jdk[version]

This question still seems relevant, and the answer seems to be a moving target.

On my debian system (buster):

> update-java-alternatives -l java-1.11.0-openjdk-amd64 1111 /usr/lib/jvm/java-1.11.0-openjdk-amd64 

However, if you actually go look there, you’ll see there are multiple directories and symbolic links placed there by the package system to simplify future maintenance.

The actual directory is java-11-openjdk-amd64 , with another symlink of default-java . There is also an openjdk-11 directory, but it appears to only contain a source.zip file.

Given this, for Debian ONLY, I would guess the best value to use is /usr/lib/jvm/default-java , as this should always be valid, even if you decide to install a totally different version of java, or even switch vendors.

The normal reason to want to know the path is because some application wants it, and you probably don’t want that app to break because you did an upgrade that changed version numbers.

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How to install Java JDK on Ubuntu

This tutorial shows you how to install OpenJDK 8, 11, 16, and other JDK builds on Ubuntu 20.

1. APT Install JDK (OpenJDK 8 and 11)

This example shows how to use apt install to install the OpenJDK 8 and 11 on Ubuntu.

1.1 We can use sudo apt search openjdk to find all available OpenJDK in the default repository. The below search result show four OpenJDK are available to install.

 $ sudo apt search openjdk openjdk-11-jdk/focal-updates,focal-security,now 11.0.10+9-0ubuntu1~20.04 amd64 [installed] OpenJDK Development Kit (JDK) openjdk-13-jdk/focal-updates 13.0.4+8-1~20.04 amd64 OpenJDK Development Kit (JDK) openjdk-14-jdk/focal-updates 14.0.2+12-1~20.04 amd64 OpenJDK Development Kit (JDK) openjdk-8-jdk/focal-updates,focal-security 8u282-b08-0ubuntu1~20.04 amd64 OpenJDK Development Kit (JDK) # . 

1.2 If we want to install Java 8.

 $ sudo apt install openjdk-8-jdk 

1.3 If we want to install Java 11.

 $ sudo apt install openjdk-11-jdk 

1.4 Where is JDK installed?
The apt install the Java JDK at this path /usr/lib/jvm .

 ls -lsa /usr/lib/jvm 4 drwxr-xr-x 5 root root 4096 Mac 29 15:06 . 4 drwxr-xr-x 125 root root 4096 Mac 5 11:51 .. 0 lrwxrwxrwx 1 root root 21 Jul 16 2020 java-1.11.0-openjdk-amd64 -> java-11-openjdk-amd64 4 -rw-r--r-- 1 root root 2044 Jan 20 10:32 .java-1.11.0-openjdk-amd64.jinfo 4 drwxr-xr-x 9 root root 4096 Feb 18 13:54 java-11-openjdk-amd64 0 lrwxrwxrwx 1 root root 20 Jan 20 11:59 java-1.8.0-openjdk-amd64 -> java-8-openjdk-amd64 4 -rw-r--r-- 1 root root 2764 Jan 20 11:59 .java-1.8.0-openjdk-amd64.jinfo 4 drwxr-xr-x 7 root root 4096 Mac 29 15:06 java-8-openjdk-amd64 4 drwxr-xr-x 3 root root 4096 Feb 18 13:53 openjdk-11 

1.5 And the global /usr/bin/java is linked to one of the installed JDK.

 $ which java /usr/bin/java $ ls -lsa /usr/bin/java 0 lrwxrwxrwx 1 root root 22 Sep 14 2020 /usr/bin/java -> /etc/alternatives/java $ ls -lsa /etc/alternatives/java 0 lrwxrwxrwx 1 root root 46 Mac 29 15:15 /etc/alternatives/java -> /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java 

1.6 We can use java -version to verify if Java JDK is installed correctly.

 $ java -version openjdk version "1.8.0_282" OpenJDK Runtime Environment (build 1.8.0_282-8u282-b08-0ubuntu1~20.04-b08) OpenJDK 64-Bit Server VM (build 25.282-b08, mixed mode) 

2. Install JDK manually (OpenJDK 16)

If we want the latest Java JDK, for example JDK 16, early-access builds, or other JDK builds like AdoptOpenJDK, which are not available in the Ubuntu default repository. We can still download the JDK and install it on Ubuntu manually.

This example will install the JDK 16.

2.2 Extracts the downloaded JDK to /opt/jdk-16 .

 $ sudo mkdir /opt/jdk-16 $ sudo tar -zxf ~/Downloads/openjdk-16_linux-x64_bin.tar.gz -C /opt/jdk-16 $ ls -lsa /opt/jdk-16 ls -lsa /opt/jdk-16 total 36 4 drwxr-xr-x 8 root root 4096 Mac 10 13:18 . 4 drwxr-xr-x 5 root root 4096 Mac 15 14:09 .. 4 drwxr-xr-x 2 root root 4096 Mac 10 13:18 bin 4 drwxr-xr-x 5 root root 4096 Mac 10 13:18 conf 4 drwxr-xr-x 3 root root 4096 Mac 10 13:18 include 4 drwxr-xr-x 2 root root 4096 Mac 10 13:18 jmods 4 drwxr-xr-x 69 root root 4096 Mac 10 13:18 legal 4 drwxr-xr-x 5 root root 4096 Mac 10 13:18 lib 4 -rw-r--r-- 1 10668 10668 1133 Feb 8 19:40 release 

2.3 This update-alternatives —install /usr/bin/java java let the Ubuntu know there is one more option /opt/jdk-16/bin/java for the /etc/alternatives/java link.

 $ sudo update-alternatives --install /usr/bin/java java /opt/jdk-16/bin/java 100 

2.4 Update the /etc/alternatives/java link.

The below result shows 5 JDK installed on this Ubuntu; choose option 2 for the above extracted JDK 16 /opt/jdk-16/bin/java .

 $ sudo update-alternatives --config java There are 4 choices for the alternative java (providing /usr/bin/java). Selection Path Priority Status ------------------------------------------------------------ 0 /usr/lib/jvm/java-11-openjdk-amd64/bin/java 1111 auto mode 1 /opt/jdk-15/bin/java 100 manual mode 2 /opt/jdk-16/bin/java 100 manual mode 3 /usr/lib/jvm/java-11-openjdk-amd64/bin/java 1111 manual mode * 4 /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java 1081 manual mode Press to keep the current choice[*], or type selection number: 2 update-alternatives: using /opt/jdk-16/bin/java to provide /usr/bin/java (java) in manual mode 

 $ java -version openjdk version "16" 2021-03-16 OpenJDK Runtime Environment (build 16+36-2231) OpenJDK 64-Bit Server VM (build 16+36-2231, mixed mode, sharing) 

3. Install Oracle JDK on Ubuntu

We need to create an Oracle account to download the Oracle JDK. Please visit the official Oracle JDK link to download the JDK and follow the above install JDK manually, and it works the same.

The Oracle JDK 11 and above are paid products, and you need a license for production use. However, it’s still free to download for development and testing.

Note
In the old days, we can install the Oracle JDK in the following ways, but it failed now; please read New Oracle Java 11 Installer For Ubuntu

Install Oracle JDK 11 (Not working now)

 $ sudo add-apt-repository ppa:linuxuprising/java $ sudo apt update $ sudo apt install oracle-java11-installer 

 $ sudo add-apt-repository ppa:webupd8team/java $ sudo apt update $ sudo apt install oracle-java8-installer 

4. Switch between different JDK versions

4.1 Review the relationship for /usr/bin/java and /etc/alternatives/java .

 $ which java /usr/bin/java $ ls -lsa /usr/bin/java 0 lrwxrwxrwx 1 root root 22 Sep 14 2020 /usr/bin/java -> /etc/alternatives/java $ ls -lsa /etc/alternatives/java 0 lrwxrwxrwx 1 root root 46 Mac 29 15:15 /etc/alternatives/java -> /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java 

4.2 For any new downloaded JDK, run update-alternatives —install /usr/bin/java java to let Ubuntu know there is an extra option for the /usr/bin/java .

4.3 For multiple installed JDK, we can run update-alternatives —config java select which JDK to use.

 $ sudo update-alternatives --config java There are 4 choices for the alternative java (providing /usr/bin/java). Selection Path Priority Status ------------------------------------------------------------ 0 /usr/lib/jvm/java-11-openjdk-amd64/bin/java 1111 auto mode 1 /opt/jdk-15/bin/java 100 manual mode * 2 /opt/jdk-16/bin/java 100 manual mode 3 /usr/lib/jvm/java-11-openjdk-amd64/bin/java 1111 manual mode 4 /usr/lib/jvm/java-8-openjdk-amd64/jre/bin/java 1081 manual mode 

5. Add JAVA_HOME to Ubuntu environment variable

Many servers, frameworks, and tools depend on the JAVA_HOME environment variable to find the installed Java. On Ubuntu, we can add the JAVA_HOME to the system-wide environment variables – /etc/environment.

5.1 Open the file /etc/environment with your favorite text editors like vi, vim, or nano.

5.2 Add JAVA_HOME at a new line and point it to one of the installed JDK.

 PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin" JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64/ 

5.3 source /etc/environment to reflect the changes in the current session.

 $ source /etc/environment $ echo $JAVA_HOME /usr/lib/jvm/java-11-openjdk-amd64/ 

Note
The new changes will disappear if we close the current session or reopen a new terminal because a new shell does not trigger the /etc/environment . Try to restart the Ubuntu or login again; the new changes in /etc/environment will apply automatically.

6. References

mkyong

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