radosgw-admin: 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/radosgw-admin - from package: ceph-radosgw

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

On Debian possible default full paths are:

/usr/bin/radosgw-admin - from package: radosgw

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

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