foo-yc20: 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/foo-yc20 - from package: foo-yc20

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

Error in other languages:
foo-yc20: bevel nie gevind nie
foo-yc20: comandă negăsită
foo-yc20: comando não encontrado
foo-yc20: commande introuvable
foo-yc20: command not found
foo-yc20: käsku ei ole
foo-yc20: không tìm thấy lệnh
foo-yc20: komanda nerasta
foo-yc20: Kommando nicht gefunden.
foo-yc20: kommandot finns inte
foo-yc20: komut yok
foo-yc20: nie znaleziono polecenia
foo-yc20: níor aimsíodh an t-ordú
foo-yc20: no se encontró la orden
foo-yc20: no s'ha trobat l'ordre
foo-yc20: opdracht niet gevonden
foo-yc20: parancs nem található
foo-yc20: perintah tidak ditemukan
foo-yc20: príkaz nenájdený
foo-yc20: příkaz nenalezen
foo-yc20: команда не найдена
foo-yc20: командата не е открита
foo-yc20: 命令找不到
foo-yc20: コマンドが見つかりません