How to uninstall linux-image-2.6.32-21-server from Ubuntu
To uninstall just linux-image-2.6.32-21-server package itself from Ubuntu execute on terminal:
sudo apt-get remove linux-image-2.6.32-21-server
Uninstall linux-image-2.6.32-21-server and it's dependent packages
To uninstall the linux-image-2.6.32-21-server package and any other dependant package which are no longer needed on Ubuntu.
sudo apt-get autoremove linux-image-2.6.32-21-server
If you also want to delete configuration and/or data files of linux-image-2.6.32-21-server from Ubuntu then this will work:
sudo apt-get purge linux-image-2.6.32-21-server
To delete configuration and/or data files of linux-image-2.6.32-21-server and it's dependencies from Ubuntu then execute:
sudo apt-get autoremove --purge linux-image-2.6.32-21-server
linux-image-2.6.32-21-server package information
Linux kernel image for version 2.6.32 on x86_64
This package contains the Linux kernel image for version 2.6.32 on x86_64. Also includes the corresponding System.map file, the modules built by the packager, and scripts that try to ensure that the system is not left in an unbootable state after an update. Supports Server processors. Geared toward 64 bit server systems. You likely do not want to install this package directly. Instead, install the linux-server meta-package, which will ensure that upgrades work correctly, and that supporting packages are also installed.
More information about apt-get remove
Advanced Package Tool, or APT, is a free software user interface that works with core libraries to handle the installation and removal of software on Debian, Ubuntu and other Linux distributions. APT simplifies the process of managing software on Unix-like computer systems by automating the retrieval, configuration and installation of software packages, either from precompiled files or by compiling source code.
apt-get is the command-line tool for handling packages, and may be considered the user's "back-end" to other tools using the APT library.
apt-get remove is identical to install except that packages are removed instead of installed. Note that removing a package leaves its configuration files on the system. If a plus sign is appended to the package name (with no intervening space), the identified package will be installed instead of removed.