polarssl_md5sum: 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/polarssl_md5sum - from package: libpolarssl-runtime

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

Error in other languages:
polarssl_md5sum: bevel nie gevind nie
polarssl_md5sum: comandă negăsită
polarssl_md5sum: comando não encontrado
polarssl_md5sum: commande introuvable
polarssl_md5sum: command not found
polarssl_md5sum: käsku ei ole
polarssl_md5sum: không tìm thấy lệnh
polarssl_md5sum: komanda nerasta
polarssl_md5sum: Kommando nicht gefunden.
polarssl_md5sum: kommandot finns inte
polarssl_md5sum: komut yok
polarssl_md5sum: nie znaleziono polecenia
polarssl_md5sum: níor aimsíodh an t-ordú
polarssl_md5sum: no se encontró la orden
polarssl_md5sum: no s'ha trobat l'ordre
polarssl_md5sum: opdracht niet gevonden
polarssl_md5sum: parancs nem található
polarssl_md5sum: perintah tidak ditemukan
polarssl_md5sum: príkaz nenájdený
polarssl_md5sum: příkaz nenalezen
polarssl_md5sum: команда не найдена
polarssl_md5sum: командата не е открита
polarssl_md5sum: 命令找不到
polarssl_md5sum: コマンドが見つかりません