vdb-encrypt: 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/vdb-encrypt - from package: sra-toolkit

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

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