dh_md5sums: 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/dh_md5sums - from package: debhelper

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

Error in other languages:
dh_md5sums: bevel nie gevind nie
dh_md5sums: comandă negăsită
dh_md5sums: comando não encontrado
dh_md5sums: commande introuvable
dh_md5sums: command not found
dh_md5sums: käsku ei ole
dh_md5sums: không tìm thấy lệnh
dh_md5sums: komanda nerasta
dh_md5sums: Kommando nicht gefunden.
dh_md5sums: kommandot finns inte
dh_md5sums: komut yok
dh_md5sums: nie znaleziono polecenia
dh_md5sums: níor aimsíodh an t-ordú
dh_md5sums: no se encontró la orden
dh_md5sums: no s'ha trobat l'ordre
dh_md5sums: opdracht niet gevonden
dh_md5sums: parancs nem található
dh_md5sums: perintah tidak ditemukan
dh_md5sums: príkaz nenájdený
dh_md5sums: příkaz nenalezen
dh_md5sums: команда не найдена
dh_md5sums: командата не е открита
dh_md5sums: 命令找不到
dh_md5sums: コマンドが見つかりません