avr-man: 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-man - from package: avr-libc

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

On Debian possible default full paths are:

/usr/bin/avr-man - from package: avr-libc

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

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