help2man: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/help2man - from package: help2man

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/help2man - from package: help2man

You may install the required package with command apt-get install {package}

Error in other languages:
help2man: bevel nie gevind nie
help2man: comandă negăsită
help2man: comando não encontrado
help2man: commande introuvable
help2man: command not found
help2man: käsku ei ole
help2man: không tìm thấy lệnh
help2man: komanda nerasta
help2man: Kommando nicht gefunden.
help2man: kommandot finns inte
help2man: komut yok
help2man: nie znaleziono polecenia
help2man: níor aimsíodh an t-ordú
help2man: no se encontró la orden
help2man: no s'ha trobat l'ordre
help2man: opdracht niet gevonden
help2man: parancs nem található
help2man: perintah tidak ditemukan
help2man: príkaz nenájdený
help2man: příkaz nenalezen
help2man: команда не найдена
help2man: командата не е открита
help2man: 命令找不到
help2man: コマンドが見つかりません