avr-as: 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/avr-as - from package: avr-binutils

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

On Debian possible default full paths are:

/usr/bin/avr-as - from package: binutils-avr

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

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