jls: 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/jls - from package: sleuthkit

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

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