redis-benchmark: command not found

Have You tried accessing the binary with the full path?

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/redis-benchmark - from package: redis

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

On Debian possible default full paths are:

/usr/bin/redis-benchmark - from package: redis-tools

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