cephfs: 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 CentOS possible default full paths are:

/usr/bin/cephfs - from package: ceph

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/cephfs - from package: ceph-fs-common

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

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