jetring-checksum: 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/jetring-checksum - from package: jetring

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