fqdn-etc-host.sh: 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/share/drbl/bin/fqdn-etc-host.sh - from package: drbl

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

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