euca-associate-route-table: 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-associate-route-table - from package: euca2ools

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

On Debian possible default full paths are:

/usr/bin/euca-associate-route-table - from package: euca2ools

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

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