approx: 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/sbin/approx - from package: approx

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

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