Ant needs tools.jar and unable to find it
On Debian, after installing Ant with apt-get install ant, I've encountered the same error when running it:
Unable to locate tools.jar. Expected to find it in /usr/lib/jvm/java-6-openjdk-amd64/lib/tools.jar
Indeed, there's no mention of any tools.jar anywhere in /usr/lib, although /usr/lib/jvm/java-6-openjdk-amd64 itself does exist.
https://packages.debian.org/search?searchon=contents&keywords=java-6-openjdk-amd64%2Flib%2Ftools.jar
As per the search above, java-6-openjdk-amd64/lib/tools.jar appears to be part of openjdk-6-jdk, which indeed didn't get installed with ant (since it's only marked as suggested (https://packages.debian.org/wheezy/ant)).
apt-get install openjdk-6-jdk
Note: On CentOS / RHEL installing java-1.x.0-openjdk will not be enough. Also install java-1.x.0-openjdk-devel.
It seems like you can have Java installed in /usr/lib/jvm/java-6-openjdk but only have the JRE, not the JDK. This fixed it for me:
sudo apt-get install openjdk-6-jdk
It's there on my machine. I'm running Sun JDK 1.6.0_21 on Windows XP SP3.
Are you sure you have the JDK? Is it possible that you only have the JRE?