pre-grohtml: 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/pre-grohtml - from package: groff

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

On Debian possible default full paths are:

/usr/bin/pre-grohtml - from package: groff

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

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