Hi,i've read most post about driver and patch for rtl8187 and i read the link refer to patch for this device on Aircrack-ng site,but during the installation after doing make appear this error :

bt rtl8187_linux_26.1010.0622.2006 # make
rm -f ieee80211/Module.symvers 2>/dev/null
rm -f ieee80211/Modules.symvers 2>/dev/null
make -C ieee80211 all
make[1]: Entering directory `/root/Desktop/wep/rtl8187_linux_26.1010.0622.2006/ieee80211'
make -C /lib/modules/2.6.21.5/build M=/root/Desktop/wep/rtl8187_linux_26.1010.0622.2006/ieee80211 modules
make: Entering an unknown directory
make: *** /lib/modules/2.6.21.5/build: No such file or directory. Stop.
make: Leaving an unknown directory
make[1]: *** [modules] Error 2
make[1]: Leaving directory `/root/Desktop/wep/rtl8187_linux_26.1010.0622.2006/ieee80211'
make: *** [all] Error 2

how resolve it?thanks