If the nslookup or host command is not found on your Debian or Ubuntu Linux system, it is likely that the package containing these commands is not installed.
To install the package containing these commands, run the following command:
sudo apt update sudo apt install dnsutils
This will install the dnsutils package, which includes the nslookup and host commands.
After the installation is complete, you should be able to use the nslookup and host commands to perform DNS lookups.
For example, to perform a DNS lookup for the domain example.com, you can use the nslookup command like this:
nslookup example.com
Or, you can use the host command like this:
host example.com