jmkmf: 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/jmkmf - from package: dist

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