You will receive an error like the following, where COMMAND is the missing command:
/bin/sh: COMMAND: command not found
This will occur if the package containing the command is not installed, or if the PATH shell variable does not include the directory that contains it.
1) Check if the command is provided by a package. In this example, we will use the whois command. You will need to replace whois with the command you received the error for.
# yum provides whois
Loaded plugins: fastestmirror, universal-hooks
Loading mirror speeds from cached hostfile
* EA4: 184.108.40.206
* cpanel-addons-production-feed: 220.127.116.11
* cpanel-plugins: 18.104.22.168
* epel: pubmirror1.math.uh.edu
whois-5.1.1-2.el7.x86_64 : Improved WHOIS client
Repo : base
2) The above lets us know that the whois command is available in the whois package. If a package is returned, it can be installed as below, again using whois as an example. If a result is not returned, the command may have been typed incorrectly or may exist in a repository not configured on the server. It is also possible that the command is not provided in a package at all.
# yum install whois
3) If the package is already installed, you may need to adjust your PATH shell variable to include the containing directory. You can verify this by checking the current value of PATH like so.
# echo $PATH