innupgrade: 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/lib/news/bin/innupgrade - from package: inn2

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

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