shisa: 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/shisa - from package: shisa

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

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