pg_dropcluster: command not found

Have You tried accessing the binary with the full path?

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH

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_dropcluster - from package: postgresql-common

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