A Potential Disaster Using CPIO

We have a shell script that we use to restore files from our nightly backup tape. This script uses 'cpio' . There is a potential disaster waiting to happen if you are prompted to rename the file you want to restore. I believe most UNIX variants (We have SCO Openserver 5.0) interpret a response with a single period to restore the file with the same path and name. The biggest error of my life occurred when I accidentally entered two consecutive periods {..}. What happened was that 'cpio' copied my file that I was trying to restore over the top of {..} (parent directory indicator) in the root directory. All heck broke loose after that. It took a while to figure out what happened and almost all night to fix it. We actually at one point were considering re-loading the operating system and restoring all our files from the night before. What was really scary is that 'cpio' would not work at that point so there was no way to restore any files. Also 'ls', 'pwd', did not work along with any other commands that created temporary work files (quite a few).

If this ever happens to someone (I would not wish this on anybody's worst enemy) the way to fix it is to first unlink {..} from {.} and then remove {..} (UNIX will not allow you to remove it unless it is unlinked first) and then link {..} back to {.} . In other words unlink dot dot from dot and then remove dot dot and then link dot dot back to dot (say that out loud and any layman will run for cover).

This seems like a very easy error to happen especially if you hold down the period key too long. I wonder if this has ever happened before or if there is some full proof measures to prevent this from happening (even if you are superuser).

Publish your articles, comments, book reviews or opinions here!

Comments?

More Articles by Ron Kopp

Jump to Comments

Many of the products and books I review are things I purchased for my own use. Some were given to me specifically for the purpose of reviewing them. I resell or can earn commissions from the sale of some of these items. Links within these pages may be affiliate links that pay me for referring you to them. That's mostly insignificant amounts of money; whenever it is not I have made my relationship plain. I also may own stock in companies mentioned here. If you have any question, please do feel free to contact me.

Specific links that take you to pages that allow you to purchase the item I reviewed are very likely to pay me a commission. Many of the books I review were given to me by the publishers specifically for the purpose of writing a review. These gifts and referral fees do not affect my opinions; I often give bad reviews anyway.

We use Google third-party advertising companies to serve ads when you visit our website. These companies may use information (not including your name, address, email address, or telephone number) about your visits to this and other websites in order to provide advertisements about goods and services of interest to you. If you would like more information about this practice and to know your choices about not having this information used by these companies, click here.