nilfs-clean: 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/sbin/nilfs-clean - from package: nilfs-tools

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

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