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GNU Info (tar.info)how to updateHow to Update an Archive Using `--update' ......................................... You must use file name arguments with the `--update' (`-u') operation. If you don't specify any files, `tar' won't act on any files and won't tell you that it didn't do anything (which may end up confusing you). To see the `--update' option at work, create a new file, `classical', in your practice directory, and some extra text to the file `blues', using any text editor. Then invoke `tar' with the `update' operation and the `--verbose' (`-v') option specified, using the names of all the files in the practice directory as file name arguments: $ tar --update -v -f collection.tar blues folk rock classical blues classical $ Because we have specified verbose mode, `tar' prints out the names of the files it is working on, which in this case are the names of the files that needed to be updated. If you run `tar --list' and look at the archive, you will see `blues' and `classical' at its end. There will be a total of two versions of the member `blues'; the one at the end will be newer and larger, since you added text before updating it. (The reason `tar' does not overwrite the older file when updating it is because writing to the middle of a section of tape is a difficult process. Tapes are not designed to go backward. Note: Media, for more information about tapes. `--update' (`-u') is not suitable for performing backups for two reasons: it does not change directory content entries, and it lengthens the archive every time it is used. The GNU `tar' options intended specifically for backups are more efficient. If you need to run backups, please consult Note: Backups. automatically generated by info2www version 1.2.2.9 |