eulb-deregister-instances-from-lb: 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 CentOS possible default full paths are:

/usr/bin/eulb-deregister-instances-from-lb - from package: euca2ools

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/eulb-deregister-instances-from-lb - from package: euca2ools

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

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