sumtool: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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/sbin/sumtool - from package: mtd-utils

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