lksh: 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:

/bin/lksh - from package: mksh

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

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