jacksum: 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/jacksum - from package: jacksum

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

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