librados-config: 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/librados-config - from package: ceph

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

On Debian possible default full paths are:

/usr/bin/librados-config - from package: librados-dev

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

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