pgbouncer: 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/sbin/pgbouncer - from package: pgbouncer

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

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