slonik_init_cluster: 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/slonik_init_cluster - from package: slony1-2-bin

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

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