redcloth: 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 Debian possible default full paths are:

/usr/bin/redcloth - from package: ruby-redcloth

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

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