tthsum: 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
/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/tthsum - from package: tthsum

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