rcceph: 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/sbin/rcceph - from package: ceph

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

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