Skip to main content

Multiple jvm on one linux box

For some reason, you need to use more than one version of jdk on same linux machine. First thing to do is install jdk, you can download from sun. Follow their installation instruction then you should have jdk install in /usr/java/jdk1.6.0_01. but jre still gcj
[root@mail ~]# java -version
java version "1.4.2"
gij (GNU libgcj) version 4.0.2 20051125 (Red Hat 4.0.2-8)

Copyright (C) 2005 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
[root@mail ~]#

So use alternatives command to check
[root@mail ~]# alternatives --display java
java - status is auto.
 link currently points to /usr/lib/jvm/jre-1.4.2-gcj/bin/java
/usr/lib/jvm/jre-1.4.2-gcj/bin/java - priority 1420
 slave rmiregistry: /usr/lib/jvm/jre-1.4.2-gcj/bin/rmiregistry
 slave jre_exports: /usr/lib/jvm-exports/jre-1.4.2-gcj
 slave jre: /usr/lib/jvm/jre-1.4.2-gcj
Current `best' version is /usr/lib/jvm/jre-1.4.2-gcj/bin/java.
[root@mail ~]#

add 'sun java' to alternative,config,and check again
[root@mail ~]# alternatives --install /usr/bin/java java /usr/java/jdk1.6.0_01/bin/java 2 
[root@mail ~]# alternatives --config java 
There are 2 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
*+ 1           /usr/lib/jvm/jre-1.4.2-gcj/bin/java
   2           /usr/java/jdk1.6.0_01/bin/java

Enter to keep the current selection[+], or type selection number: 2
[root@mail ~]# java -version
java version "1.6.0_01"
Java(TM) SE Runtime Environment (build 1.6.0_01-b06)
Java HotSpot(TM) Client VM (build 1.6.0_01-b06, mixed mode, sharing)
[root@mail ~]#


Note: For my ubuntu box I get java from backport extra repos by add this two line in /etc/apt/sources.list
deb http://archive.ubuntu.com/ubuntu dapper-backports main restricted universe multiverse
deb-src http://archive.ubuntu.com/ubuntu dapper-backports main restricted universe multiverse

then use these command to install and config
pnix@pnix-a7:~$sudo apt-get install sun-java6-jdk sun-java6-plugin
pnix@pnix-a7:~$sudo update-alternatives --config java
Labels:

Comments

Anonymous said…
Great post and screen shots! Saved the day, ty
February 24, 2011 at 10:39 PM
Anonymous said…
Thanks.

Hasan Ali Özaslan
June 13, 2013 at 7:50 PM
Post a Comment

Popular posts from this blog

Fixing sendmail take a long time to start

I notice that my database box[FC6+Oracle10.2] take along time to startup. Sendmail and sm-client very very slow to start[ about 5 minutes ]. There's something wrong in /etc/hosts file. 'newalises' command take long time to update and finish with error below. [root@ora10g ~]# newaliases WARNING: local host name (ora10g) is not qualified; see cf/README: WHO AM I? /etc/aliases: 76 aliases, longest 10 bytes, 765 bytes total [root@ora10g ~]# cat /etc/hosts # Do not remove the following line, or various programs # that require network functionality will fail. 127.0.0.1 localhost.localdomain localhost 192.168.1.55 ora10g [root@ora10g ~]# To fix this, custom hostname[ora10g] need to append to localhost line in /etc/hosts. [root@ora10g ~]# cat /etc/hosts # Do not remove the following line, or various programs # that require network functionality will fail. 127.0.0.1 localhost.localdomain localhost ora10g 192.168.1.55 ora10g [root@ora10g ~]# newaliases /etc/alia
11 comments
Read more

Too many open files

Last week tomcat log file report many error about "Too many open files" when it has high traffic. Some in catalina_log say 2007-04-07 16:13:40 HttpProcessor[80][272] Starting background thread 2007-04-07 16:13:40 HttpConnector[80] accept: java.net.SocketException: Too many open files and here is from localhost_log 2007-04-07 16:13:40 StandardWrapperValve[myservlet]: Servlet.service() for servlet myservlet threw exception java.io.FileNotFoundException: /home/log/mylog_070407.log (Too many open files) This is because too many file descriptors're opened by tomcat. File descriptor can be limited in both system level and shell level. To check maximum number of fd in system type 'cat /proc/sys/fs/file-max'. In my case it is 65536(someone said it should set to 200000). Tomcat error when try to open socket number 272 so I think 65536 is ok for me for now. Anyway if u want to set it add 'fs.file-max = 200000' to /etc/sysctl.conf pnix@pnix-a7:~$ cat /proc/sys/fs/fil
15 comments
Read more

using Class.getResource() load resource file in Eclipse

There are many ways to load resource file in java app. What sun recommended is using Class.getResource(" resource_name ") or Class.getResourceAsStream(" resource_name ") then you will get URL and InputStream respectively. If resource_name is specified without "/", it will be prepend with Class package. So resource file must be in same place[folder structure] as the Class. What I love to do is call getResource() with "/" and put resource file at the root of package. This way i can have separate resource folder. below is in Eclipse, 1. From Package explorer right click src folder->click import 2. In import dialog, Choose General->File System ->next 3. from directory:->Browse to your resource folder. 4. to folder:-> I add "resource" as a folder name under src folder. then click "Finish". In the code, load resource with this.getClass().getResource("/resource/buttons1.png") or this.getClass().getResourceAs
37 comments
Read more