ceph_test_rados_api_io: 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/ceph_test_rados_api_io - from package: ceph-test

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

On Debian possible default full paths are:

/usr/lib/ceph/bin/ceph_test_rados_api_io - from package: ceph-test

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

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