These days there are many easy ways to root nexus one and other android phones, or you can avoid the hassle of rooting by simply installing a pre rooted firmware on your android phone and there are many one click tools which easily allows you to root your nexus one.
Superboot is one such tool which is a boot.img that when flashed, will root your device the first time you boot (installing su and the superuser APK). No need to flash the system partition, no need to use ADB, no messing with the contents of your data partition, no overwriting the shipped ROM on your device, just flash the boot image using the instructions below.
1. Download the Superboot zip file above and extract to a directory [ as per applied for your android phone from the links given below ]
2. Put your device in bootloader mode – Turn off the phone then press power button to boot and hold the trackball to enter the bootloader.
Then run the command as per your OS Version, given below.
For WINDOWS Users – double click ‘install-superboot-windows.bat’
For MAC Users – Open a terminal window to the directory containing the files, and type ‘chmod +x install-superboot-mac.sh’ followed by ‘./install-superboot-mac.sh’
For LINUX Users – Open a terminal window to the directory containing the files, and type ‘chmod +x install-superboot-linux.sh’ followed by ‘./install-superboot-linux.sh’
Refer this page for the download links for superboot as per your firmware version.
PS: If you see the message, downloading boot.img and then nothing happened after using tool, find some other tool or way to root your android phone.