vdb-lock: 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-lock - from package: sra-toolkit

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

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