unworkable: 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/unworkable - from package: unworkable

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

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