ceph_bench_log: 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_bench_log - 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_bench_log - from package: ceph-test

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

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