netselect-apt: 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/netselect-apt - from package: netselect-apt

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

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