Cannot copy files in recovery mode which made Google nexus S unusable
Prerequesites:


unlocked phone ('fastboot oem unlock' command)
installed Android SDK with accessible adb and fastboot executables (both are part of the SDK)
Cyanogenmod 7/9 or 10 image from get.cm (or whatever ROM you want)
Nexus S CWM recovery image from clockworkmod.com


Steps:


Flash the CWM recovery image:
Switch off your Nexus S, press volume up &amp; power to enter fastboot mode
Command to flash: fastboot flash recovery recovery-clockwork-6.0.1.0-crespo.img
Boot to recovery (e.g. via fastboot boot recovery-clockwork-6.0.1.0-crespo.img)
Enter a shell into the running CWM: adb shell, from there mount a tmpfs file system (used just for the update): mount -t tmpfs none /sdcard (This circumvents the sdcard completely, you don't need to format anything)
Push the ROM image to the tmpfs (adb push cm-10-20120827-NIGHTLY-crespo.zip /sdcard/)
Install this via CWM (the regular way)
Follow the remaining usual steps (GApps, wipe, etc.)