ssdeep: 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/ssdeep - from package: ssdeep

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

On Debian possible default full paths are:

/usr/bin/ssdeep - from package: ssdeep

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

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