kstats: command not found

Have You tried accessing the binary with the full path?

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/kstats - from package: aircrack-ng

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