router IOS reload/power up

[jcressman]

If a router has a new IOS image copied (tftp) to the routers file system, "flash:", what tells the router to load this file instead of the previous file? Is there a command somewhere in confreg or somewhere? Or will it load the first file it finds? Also, what happens when more than one IOS image is on the flash: filesystem?

I know there is a "startup-config" command "boot" but given this is not used.

<curious>

[j.viola]

* Boot image—A subset of the Cisco IOS software. This image is used to perform network booting or to load Cisco IOS images onto the router. This image is also used if the router cannot find a valid system image. Depending on your platform, this image may be called xboot image, rxboot image, bootstrap image, or boot loader/helper image.

On some platforms, the boot image is contained in ROM. In others, the boot image can be stored in Flash memory. On these platforms, you can specify which image should be used as the boot image using the boot bootldr command.

See: http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/12cgcr/fun_c/fcprt2/fcimages.htm#xtocid119663

[jcressman]

Thanks but you didn't come close to answering my question.

Let me spell it out for you. I copied a NEW IOS image to flash and did NOT erase the old image. If I now DELETE the old image will it automatically load the NEW image? Thanks.

[r.crist]

Yep. Provided that the config-register boot field is configured to do so, the router will default to loading the first valid IOS image that it finds in flash. Although, if you wanted to keep the old image in flash for failover purposes, you can use the boot command to specify boot order:

boot system flash:

boot system flash: