May 26, 2018

Backup-only shell

bksh is a simple some would say trivial program designed to be used as a shell by ssh or rsh-like programs. All it does it to copy its input to a restricted set of backup files.

It was made to allow administrators to create backup servers in potentially hostile environments without allowing full shell access to the server or the client.


  • tape only or file & tape backups compile-time config
  • automatic file rotation allows keeping a history of backups
  • configurable number of files kept static compile-time or dynamic
  • allows naming of backup files on command line
  • works as a restricted shell to limit access to server
  • very simple and short ANSI C code, easy to audit

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