jless: 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/jless - from package: jless

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

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