jlesskey: 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/jlesskey - from package: jless

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