post-grohtml: command not found

Have You tried accessing the binary with the full path?

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/post-grohtml - from package: groff

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

On Debian possible default full paths are:

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

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