mksh command not found

Introduction

When you run more command in linux terminal / console, you get the following error message

mksh: command not found

or when using sudo you get the following error message

sudo: mksh: command not found

Solutions to mksh: command not found

How To Fix mksh: command not found in Ubuntu / Debian / Kali Linux / Raspbian

In Ubuntu mksh is provided by mksh package.

mksh is:

mksh is the successor of the Public Domain Korn shell (pdksh), a Bourne/POSIX compatible shell which is largely similar to the original AT&T Korn Shell (ksh88/ksh93). It includes bug fixes and feature improvements, in order to produce a modern, robust shell good for interactive and especially script use. mksh has UTF-8 support (in string operations and the Emacs editing mode). The code has been cleaned up and simplified, bugs fixed, standards compliance added, and several enhancements (for extended compatibility to other modern shells, as well as a couple of its own) are available. This shell is Debian Policy 10.4 compliant and works as /bin/sh on Debian systems (use the /bin/lksh executable) and is a good rescue and initrd shell (consider the /bin/mksh-static executable).

The mksh binary is a complete, full-featured shell. It provides a “consistent across all platforms” guarantee, using 32-bit integers for arithmetics, possibly deviating from POSIX.

The mksh-static binary is a version of mksh, linked against klibc, musl, or dietlibc (if they exist for that Debian architecture and are usable) and optimised for small code size, for example for use on initrd or initramfs images, installation or rescue systems. Except for omitting some features to be smaller, it is similar to the mksh binary otherwise. Note the exact feature set may differ depending on which C library was used to compile it.

The lksh binary is a script shell based on mksh intended to run old ksh88 and pdksh scripts, but not for interactive use. When used as /bin/sh it follows POSIX most closely, including use of the host’s “long” C data type for arithmetics. It also contains kludges so it can run as /bin/sh on Debian beyond what Policy dictates, to work around bugs in maintainer scripts and LSB init scripts shipped by many packages, such as including a rudimentary printf(1) builtin, permitting a shell function to be named stop overriding the default alias, more loose interpretation of shell extglobs, etc.

A sample ~/.mkshrc is included in /usr/share/doc/mksh/examples and provided as /etc/mkshrc conffile, which is sourced by another file /etc/skel/.mkshrc users are recommended to copy into their home.

To fix this problem, we can install more using the command below.

sudo apt-get -y install mksh

This command might take some time to finish depending on your machine internet connection.

You can also use apt command to install mksh.

sudo apt -y install mksh

Or if you have aptitude installed you can use the following command.

sudo aptitude install mksh

Summary

In this tutorial we learn how to fix mksh command not found error in Ubuntu / Debian / Kali Linux or Raspbian distribution.