euca-accept-vpc-peering-connection: command not found

Have You tried accessing the binary with the full path?

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-accept-vpc-peering-connection - from package: euca2ools

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