Login as root user.
edit the following file
/boot/grub/mentu.lst
you could see list of all installed OS here as follows:
Note: I have installed Ubuntu and XP in my machine
title Ubuntu 8.10, kernel 2.6.27-7-generic
uuid 1d034dd4-58c3-4ae9-abc0-c1b5e4591639
kernel /boot/vmlinuz-2.6.27-7-generic root=UUID=1d034dd4-58c3-4ae9-abc0-c1b5e4591639 ro quiet splash
initrd /boot/initrd.img-2.6.27-7-generic
title Ubuntu 8.10, kernel 2.6.27-7-generic (recovery mode)
uuid ....
kernel ....
title Ubuntu 8.10, memtest86+
uuid ....
kernel ....
title Other operating systems:
root ....
title Microsoft Windows XP Home Edition
root ....
The id start from 0.
i.e.
0 = Ubuntu 8.10, kernel 2.6.27-7-generic
1 = Ubuntu 8.10, kernel 2.6.27-7-generic (recovery mode)
2 = Ubuntu 8.10, memtest86+
3 = Other operating systems:
4 = Microsoft Windows XP Home Edition
The following line is taking care of which OS to boot by default
default 0
this means by default Ubuntu 8.10, kernel 2.6.27-7-generic will be booted
If we want to boot XP as default, change this line to
default 4
save the file. When you boot next time by default XP will be booted.
Thursday, June 18, 2009
Tuesday, June 16, 2009
java UnsupportedClassVersionError
While deploy java code into tomcat, it thrown exception as follows
SEVERE: Exception starting filter struts
java.lang.UnsupportedClassVersionError: Bad version number in .class file (unable to load class jcaptcha4struts2.core.actions.support.CaptchaImageResult)
at org.apache.catalina.loader.WebappClassLoader.findClassInternal( WebappClassLoader.java:1851)
at org.apache.catalina.loader.WebappClassLoader.findClass( WebappClassLoader.java:890)
.......
.......
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
17 Mar, 2009 1:29:25 PM org.apache.catalina.core.ApplicationContext log
INFO: Closing Spring root WebApplicationContext
The problem is version conflict [development machine java version is 1.5 but machine where i deploy has the 1.6 version]
To fix this problem we need to install java-1.6 version in the deployment machine.
SEVERE: Exception starting filter struts
java.lang.UnsupportedClassVersionError: Bad version number in .class file (unable to load class jcaptcha4struts2.core.actions.support.CaptchaImageResult)
at org.apache.catalina.loader.WebappClassLoader.findClassInternal( WebappClassLoader.java:1851)
at org.apache.catalina.loader.WebappClassLoader.findClass( WebappClassLoader.java:890)
.......
.......
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
17 Mar, 2009 1:29:25 PM org.apache.catalina.core.ApplicationContext log
INFO: Closing Spring root WebApplicationContext
The problem is version conflict [development machine java version is 1.5 but machine where i deploy has the 1.6 version]
To fix this problem we need to install java-1.6 version in the deployment machine.
Monday, June 15, 2009
JSP form getting submitted twice
When i was working in the struts2,hibernate and spring technology, strangely "null pointer exception" thrown for attribute which used in the form even i give valid input.
I dig this issue and found that, struts action called twice when i request for the URL. Again this also crazy for me. When debug the application, found that browser sending new request if any empty 'src' in the <img> tag present in the code.
code
<img src="">
In our case browser sent second request with empty form[no data] . so obviously "null pointer exception".
so take out or give the valid image src name and this will fix the problem.
I dig this issue and found that, struts action called twice when i request for the URL. Again this also crazy for me. When debug the application, found that browser sending new request if any empty 'src' in the <img> tag present in the code.
code
<img src="">
In our case browser sent second request with empty form[no data] . so obviously "null pointer exception".
so take out or give the valid image src name and this will fix the problem.
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