raster2pgsql: 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/raster2pgsql - from package: postgis

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

Error in other languages:
raster2pgsql: bevel nie gevind nie
raster2pgsql: comandă negăsită
raster2pgsql: comando não encontrado
raster2pgsql: commande introuvable
raster2pgsql: command not found
raster2pgsql: käsku ei ole
raster2pgsql: không tìm thấy lệnh
raster2pgsql: komanda nerasta
raster2pgsql: Kommando nicht gefunden.
raster2pgsql: kommandot finns inte
raster2pgsql: komut yok
raster2pgsql: nie znaleziono polecenia
raster2pgsql: níor aimsíodh an t-ordú
raster2pgsql: no se encontró la orden
raster2pgsql: no s'ha trobat l'ordre
raster2pgsql: opdracht niet gevonden
raster2pgsql: parancs nem található
raster2pgsql: perintah tidak ditemukan
raster2pgsql: príkaz nenájdený
raster2pgsql: příkaz nenalezen
raster2pgsql: команда не найдена
raster2pgsql: командата не е открита
raster2pgsql: 命令找不到
raster2pgsql: コマンドが見つかりません