euca-describe-regions: 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/euca-describe-regions - from package: euca2ools

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

On Debian possible default full paths are:

/usr/bin/euca-describe-regions - from package: euca2ools

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

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