systemd-notify: 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/systemd-notify - from package: systemd

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

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