Keeping Users in Check
To use scp, a user must have a login and password on a machine. Usually, that corresponds to being able to log into the machine. This is not always a good idea, either for security reasons, or just because the users don't know what they're doing. scponly acts as a kind of alternative shell. It doesn't allow users to get a shell on your machine, but it does allow users to copy files using scp.
It works like this — after you've downloaded and compiled scpcopy, you add scponly to /etc/shells. It should just be one line like /usr/local/bin/scponly, or /usr/local/bin/scponlyc if you compiled scponly with the "--enable-chrooted-binary" option (more on that later). Then, either add a user and set his shell to scponly, or change an existing user's shell to scponly. Then the user can copy files using scp or one of the Secure Copy utilities found on Windows or other platforms. There's no special syntax that needs to be used after scpcopy is installed; users use scp as normal.
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- Software: scponly
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