gentoo: 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/gentoo - from package: gentoo

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

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