hashdeep: 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 CentOS possible default full paths are:

/usr/bin/hashdeep - from package: md5deep

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/hashdeep - from package: md5deep

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

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