parallel-cp: 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/parallel-cp - from package: s3ql

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

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