avr-readelf: 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-readelf - 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-readelf - from package: binutils-avr

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

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