md5Digest: 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/md5Digest - from package: gnustep-examples

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

On Debian possible default full paths are:

/usr/bin/md5Digest - from package: gnustep-examples

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

Error in other languages:
md5Digest: bevel nie gevind nie
md5Digest: comandă negăsită
md5Digest: comando não encontrado
md5Digest: commande introuvable
md5Digest: command not found
md5Digest: käsku ei ole
md5Digest: không tìm thấy lệnh
md5Digest: komanda nerasta
md5Digest: Kommando nicht gefunden.
md5Digest: kommandot finns inte
md5Digest: komut yok
md5Digest: nie znaleziono polecenia
md5Digest: níor aimsíodh an t-ordú
md5Digest: no se encontró la orden
md5Digest: no s'ha trobat l'ordre
md5Digest: opdracht niet gevonden
md5Digest: parancs nem található
md5Digest: perintah tidak ditemukan
md5Digest: príkaz nenájdený
md5Digest: příkaz nenalezen
md5Digest: команда не найдена
md5Digest: командата не е открита
md5Digest: 命令找不到
md5Digest: コマンドが見つかりません