polarssl_sha2sum: 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_sha2sum - from package: libpolarssl-runtime

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

Error in other languages:
polarssl_sha2sum: bevel nie gevind nie
polarssl_sha2sum: comandă negăsită
polarssl_sha2sum: comando não encontrado
polarssl_sha2sum: commande introuvable
polarssl_sha2sum: command not found
polarssl_sha2sum: käsku ei ole
polarssl_sha2sum: không tìm thấy lệnh
polarssl_sha2sum: komanda nerasta
polarssl_sha2sum: Kommando nicht gefunden.
polarssl_sha2sum: kommandot finns inte
polarssl_sha2sum: komut yok
polarssl_sha2sum: nie znaleziono polecenia
polarssl_sha2sum: níor aimsíodh an t-ordú
polarssl_sha2sum: no se encontró la orden
polarssl_sha2sum: no s'ha trobat l'ordre
polarssl_sha2sum: opdracht niet gevonden
polarssl_sha2sum: parancs nem található
polarssl_sha2sum: perintah tidak ditemukan
polarssl_sha2sum: príkaz nenájdený
polarssl_sha2sum: příkaz nenalezen
polarssl_sha2sum: команда не найдена
polarssl_sha2sum: командата не е открита
polarssl_sha2sum: 命令找不到
polarssl_sha2sum: コマンドが見つかりません