avogadro: 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 Debian possible default full paths are:

/usr/bin/avogadro - from package: avogadro

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

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