upsdrvctl: 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:

/sbin/upsdrvctl - from package: nut

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

On Debian possible default full paths are:

/sbin/upsdrvctl - from package: nut-server

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

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