闇月千瞳的部落格: 在 CentOS 6.4 安裝 Oracle JDK 6

安裝完 CentOS 6.4 後，我發現 CentOS 的套件庫裡也沒有 Oracle JDK 的套件，都是收錄了 OpenJDK。於是，我打算依照之前的作法自行安裝 Oracle JDK 6。在動手安裝之前，我還是爬了爬文，找了幾篇參考的文章：

安裝的步驟並不麻煩，首先自 Oracle 的網站下載了 Oracle JDK 6 的 jdk-6u45-linux-x64-rpm.bin 這個檔案，然後執行它：

$ sudo ./jdk-6u45-linux-x64-rpm.bin

接著，使用 alternatives –install 指令安裝 Oracle JDK：

$ alternatives --install /usr/bin/java java /usr/java/jdk1.6.0_45/jre/bin/java 20000
$ sudo alternatives --install /usr/bin/javaws javaws /usr/java/jdk1.6.0_45/jre/bin/javaws 20000
$ sudo alternatives --install /usr/lib/mozilla/plugins/libjavaplugin.so libjavaplugin.so /usr/java/jdk1.6.0_45/jre/lib/i386/libnpjp2.so 20000
$ sudo alternatives --install /usr/lib64/mozilla/plugins/libjavaplugin.so libjavaplugin.so.x86_64 /usr/java/jdk1.6.0_45/jre/lib/amd64/libnpjp2.so 20000
$ sudo alternatives --install /usr/bin/javac javac /usr/java/jdk1.6.0_45/bin/javac 20000
$ sudo alternatives --install /usr/bin/javac javah /usr/java/jdk1.6.0_45/bin/javah 20000
$ sudo alternatives --install /usr/bin/jar jar /usr/java/jdk1.6.0_45/bin/jar 20000

而根據爬文找到的文章，應該也可以使用像這樣的指令設定 JDK，如：

$ sudo alternatives --set /usr/bin/java java /usr/java/jdk1.6.0_45/jre/bin/java

由於我在 CentOS 6.4 裡也安裝了 java-1.7.0-openjdk-devel，所以我執行了下面這個指令選擇 Oracle JDK 作為預設的 Java：

$ sudo alternatives --config java

但，當我要修改 jar 和 javah 時，卻發現 /usr/bin/jar 及 /usr/bin/javah 消失了。

最後，我乾脆將 java-1.7.0-openjdk-devel 移除，然後手動建立 /usr/bin/java 等相關連結。 (悶)

$ ls -l /usr/bin/ja*
lrwxrwxrwx. 1 root root 21 Sep 16 12:51 /usr/bin/jar -> /etc/alternatives/jar
lrwxrwxrwx. 1 root root 27 Sep 16 12:54 /usr/bin/jarsigner -> /etc/alternatives/jarsigner
lrwxrwxrwx. 1 root root 22 Sep 16 12:40 /usr/bin/java -> /etc/alternatives/java
lrwxrwxrwx. 1 root root 23 Sep 16 12:40 /usr/bin/javac -> /etc/alternatives/javac
lrwxrwxrwx. 1 root root 25 Sep 16 12:55 /usr/bin/javadoc -> /etc/alternatives/javadoc
lrwxrwxrwx. 1 root root 23 Sep 16 12:41 /usr/bin/javah -> /etc/alternatives/javah
lrwxrwxrwx. 1 root root 23 Sep 16 12:55 /usr/bin/javap -> /etc/alternatives/javap
lrwxrwxrwx. 1 root root 24 Sep 16 12:37 /usr/bin/javaws -> /etc/alternatives/javaws

其實，/usr/bin/java 只是一個指向 /etc/alternatives/java 的連結。而 /etc/alternatives/java 才是真正指向 Java 的連結。

$ ls -l /etc/alternatives/ja*
lrwxrwxrwx. 1 root root 29 Sep 16 12:51 /etc/alternatives/jar -> /usr/java/jdk1.6.0_45/bin/jar
lrwxrwxrwx. 1 root root 35 Sep 16 12:54 /etc/alternatives/jarsigner -> /usr/java/jdk1.6.0_45/bin/jarsigner
lrwxrwxrwx. 1 root root 34 Sep 16 12:40 /etc/alternatives/java -> /usr/java/jdk1.6.0_45/jre/bin/java
lrwxrwxrwx. 1 root root 31 Sep 16 12:40 /etc/alternatives/javac -> /usr/java/jdk1.6.0_45/bin/javac
lrwxrwxrwx. 1 root root 33 Sep 16 12:55 /etc/alternatives/javadoc -> /usr/java/jdk1.6.0_45/bin/javadoc
lrwxrwxrwx. 1 root root 31 Sep 16 12:41 /etc/alternatives/javah -> /usr/java/jdk1.6.0_45/bin/javah
lrwxrwxrwx. 1 root root 31 Sep 16 12:55 /etc/alternatives/javap -> /usr/java/jdk1.6.0_45/bin/javap
lrwxrwxrwx. 1 root root 36 Sep 16 12:37 /etc/alternatives/javaws -> /usr/java/jdk1.6.0_45/jre/bin/javaws