A blog by a system administrator and programmer.


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  • 2013
    • August
      • org.apache.jasper.JasperException: java.lang.NullPointerException
        If your server can startup normally but when you try to access any jsp and the pages show the following exception.

        java.lang.NullPointerException org.apache.jsp.index_jsp._jspInit(index_jsp.java:26) org.apache.jasper.runtime.HttpJspBase.init(HttpJspBase.java:52) org.apache.jasper.servlet.

    • May
      • configure generates .infig.status: error: cannot find input file
        if you see error
        .infig.status: error: cannot find input file
        during ./configure

        it is properly due to MSDOS return character issue.

        If you system have dos2unix then just simple convert configure.ac/configure.in.
        If you don't have unix2dos ... you can try

  • 2011
    • November
      • java OutOfMemoryError Cont.
        If you still face the problem of

        java.lang.OutOfMemoryError: PermGen space

        Event you have increase the -XX:MaxPermSize.

        You can try the following jvm args.

        -XX:+CMSClassUnloadingEnabled -XX:+CMSPermGenSweepingEnabled

        Usually only java web contai

    • September
      • Java Out of Memory problems
        Java heap
        java.lang.OutOfMemoryError: Java heap

        Just simply apply -Xmx will fix the issue. But notice that one thing there have max. value for difference os.
        32bit Windows around 2G
        32bit Linux around 2.5G
        64bit I only tried to use 4G, the limit seems much h

    • February
      • my Apache production checklist
        Apache (httpd)

        Lower KeepAliveTimeout
        Default usually around 15 but I will choose from 5-10 but remember do not set the value too low as it will cause tcp overhead

        Reduce extra dns lookup for log
        HostnameLookups off

        Disable directory listing
        Remove &qu

  • 2010
    • April
      • file_get_contents getting mad?
        My blog is died for awhile after php upgrade to 5.2.13. It is full of error about putting a non-array into rsort.

        The root cause of the problem is due to the this blog store entries in file base, some of the file listing is serialized array. If you copy those content and try to unserializ

      • undefined symbol: dav_register_provider
        It has been a long time that i haven't update my apache...

        It is very easy to do with Gentoo but this time it give me an error. :(

        /usr/lib/apache2/modules/mod_dav_svn.so: undefined symbol: dav_register_provider

        After googled awhile ... i found that is related

  • 2009
    • May
      • Too many CLOSE_WAIT
        Currently I found that jetty / tomcat on Linux will have many CLOSE_WAIT on busy system especially your network is not in good condition.

        These CLOSE_WAIT will disappear untill you stop the server. These CLOSE_WAIT will use up all of you tcp connection and hang up your web server. Many pe

    • April
      • Jetty disable weak cipher
        inorder to disable weak SSL cipher in jetty you can add the xml below into SslSocketConnector

        <Set name="ExcludeCipherSuites">
        <Array type="java.lang.String">

  • 2008
    • October
      • java.io.IOException: Too many open files
        Yesterday I have face a funny java exception on my Linux server.

        java.io.IOException: Too many open files at sun.nio.ch.ServerSocketChannelImpl.accept0(Native Method) at sun.nio.ch.ServerSocketChannelImpl.accept(ServerSocketChannelImpl.java:145) at org.mortbay.jett

    • April
      • Oracle moving index to another table space
        These days I am super busy. Nearly no time to write my blog. :(

        There is so many people asking me how to move the index after created. As you know if you use plsql developer's GUI it will drop the constraint and add again with index. I don't know why it work like that but there

    • February
      • Happy lunar new year~~
        This year I am lucky that I can have a good location to take photos. :D

        For more photos please go to my gallery.

        Fireworks 2008

    • January
      • Java disk usage
        It have been a long time for me to found a way to check the disk usage in Java.

        Finially i get the solutions. It is in Java 6.0. java.io.File

        There is 2 functions.

        getTotalSpace() --- Returns the size of the partition named by this abstract pathname.

      • Happy New Year 2008
        Happy New Year to All :D

  • 2007
    • December
      • compile error of subversion
        This problem usually exist in solaris 5.7

        libtool[4766]: : is not an identifier
        make: *** [subversion/svn/svn] Segmentation Fault. (core dumped)

        Many people suggested to compile it as static link, then the problem will be solved. I have tried but without success. So that i

      • Compiler error in Solaris
        These days I have facing an error during compile DB4 in solaris 5.7.

        when I am doing configure It shows
        configure: error: C compiler cannot create executables

        Here is the error in config.log.
        configure:3855: found /usr/ucb/cc
        configure:3866: result: cc

    • November
      • syslog-ng concurrent connections exceeded
        These days I get a very funny warning in the syslog.

        syslog-ng[4484]: Number of allowed concurrent connections exceeded; num='10', max='10'

        I have googled it for a while, it seems is the default values of syslog-ng limited the concurrent connections of any s

      • Simple MySQL Replication HOWTO

        * Slave server should be newer version than the master server. It is adviced that both servers are in same version
        * Network port 3306 of both server should be avaliable
        * log-bin is enabled


        1. edit my.cnf to add log-bin and se

    • October
      • Mysql problems
        Get Error 1033 "Incorrect information in file xxxx.frm" when run REPAIR

        * Found a backup frm file if you can and overwrite the existing one
        * If you do not have frm backup, you may need to find the original "create table" statement

        1. Backup those table

      • About my blog
        It has been a long time that i want to have my own blog, but

        I am really lazy....

        I spent most of my in World of Warcraft in the past. I think i have spent almost around 2 years in the game. It is a good timing to leave the virtual world and put more time on work an