vdb-decrypt.2.3.5: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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-decrypt.2.3.5 - from package: sra-toolkit

You may install the required package with command apt-get install {package}
Error in other languages:
vdb-decrypt.2.3.5: bevel nie gevind nie
vdb-decrypt.2.3.5: comandă negăsită
vdb-decrypt.2.3.5: comando não encontrado
vdb-decrypt.2.3.5: commande introuvable
vdb-decrypt.2.3.5: command not found
vdb-decrypt.2.3.5: käsku ei ole
vdb-decrypt.2.3.5: không tìm thấy lệnh
vdb-decrypt.2.3.5: komanda nerasta
vdb-decrypt.2.3.5: Kommando nicht gefunden.
vdb-decrypt.2.3.5: kommandot finns inte
vdb-decrypt.2.3.5: komut yok
vdb-decrypt.2.3.5: nie znaleziono polecenia
vdb-decrypt.2.3.5: níor aimsíodh an t-ordú
vdb-decrypt.2.3.5: no se encontró la orden
vdb-decrypt.2.3.5: no s'ha trobat l'ordre
vdb-decrypt.2.3.5: opdracht niet gevonden
vdb-decrypt.2.3.5: parancs nem található
vdb-decrypt.2.3.5: perintah tidak ditemukan
vdb-decrypt.2.3.5: príkaz nenájdený
vdb-decrypt.2.3.5: příkaz nenalezen
vdb-decrypt.2.3.5: команда не найдена
vdb-decrypt.2.3.5: командата не е открита
vdb-decrypt.2.3.5: 命令找不到
vdb-decrypt.2.3.5: コマンドが見つかりません