fnf: 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/fnf - from package: confluence

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

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