zpool: 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/zpool - from package: zfs-fuse

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

On Debian possible default full paths are:

/sbin/zpool - from package: zfs-fuse

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

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