velveth_de: 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/velveth_de - from package: velvet

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

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