jetring-diff: 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-diff - from package: jetring

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