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We would like to upgrade to an advanced IOS image that states it requires 128mb min of Flash. We have 64mb of internal flash. We are a little confused by this as currently we are booting off of a removable compact flash card. So is it possible to run/boot off of the compact flash card? We have the min for dram of 512mb.
Yes you can boot off the compact flash card and it if is removed it will not cause a system crash. If it is removed and the switch is reloaded obviously it will fail to boot unless you have a backup IOS on bootflash.
To boot of the compact flash you just point the "boot system flash ... " command to the disk0 or disk1 slot.
Once the IOS image is loaded into memory then you can remove the compact flash card with no ill effects.
Often the new IOS images are bigger than your internal bootflash so unless you want to upgrade that then it is easier to just use a compact flash card. And if a person has access to remove the card then they can do a lot worse to your network.
Please click here for more details on upgrading software images on Catalyst 6000/6500 series switches.