I would like to make Cisco2800 IOS Upgrade.
When I am running copy tftp flash command, the question appears
Erase flash before copy (confirm)?
If I choose Yes, will only old image file be replaced or whole flash system (all files) would be deleted ?
Should I backup all files (for Instance I am using SDM, in flash SDM files sdm.tar, es.tar are located) before IOS Upgrade ?
erase flash means all files will be deleted.
You can backup the files this is a good measure. You can also choice to delete manually the old file to provide space for the new one before downloading the new one.
Usually the erase prompt appears if there isn't enough space for the new file
Hope to help
Here is a link that will help you out.