I had to update the software of a new Cisco Catalyst 4948 yesterday.
As usual I did:
copy tftp://<hostname>/<filename> bootflash:
boot system flash bootflash:<filename>
But the switch ignored the new software image.
During boot it said:
Booting first image from bootflash
Solution: The config-register was set to 0x2101 right out of the box. I had to change this to 0x2102. With this value the switch honors the bootvar and boots into the configured system image.
The config-register has different meanings on different cisco plattforms.
For the Catalyst 4948 the config-register contains a bit field explained at: