To install the KornShell (KSH) on a Debian-based Linux system, such as Ubuntu, you can use the apt-get or apt command.
To install KSH using apt-get, run the following command:
sudo apt-get install ksh
To install KSH using apt, run the following command:
sudo apt install ksh
This will install the KSH package and the necessary dependencies. Once the installation is complete, you can start using KSH by running the ksh command in a terminal.
By default, KSH is not set as the default shell for new user accounts. To set KSH as the default shell for new user accounts, you can edit the /etc/adduser.conf file and set the DSHELL variable to /bin/ksh. For example:
DSHELL=/bin/ksh
You can also change the default shell for an existing user by running the chsh command and specifying the path to the KSH executable. For example:
chsh -s /bin/ksh