op-tkdesk: 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/op-tkdesk - from package: tkdesk

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

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