repmgr: 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 Debian possible default full paths are:

/usr/bin/repmgr - from package: repmgr

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

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