Q: What is the correct syntax for the boot system command on routers and swtiches?

A:

If your router decompresses the IOS twice, as if booting twice, on every reload, you probably have the wrong syntax on the boot system command. It's picking a default version to use the second time around.

The correct syntax is:

boot system flash:c2600-i-mz.123-10b.bin

Cisco's own documentation on cco frequently gets this wrong.

On a router, you'll see the boot system command in the config. On a switch, it may not show in the config, but can see it using the show boot command. The syntax for setting it is the same in either case.