pg_lsclusters: 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/pg_lsclusters - from package: postgresql-common

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

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