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GNU Info (tar.info)AttributesHandling File Attributes ======================== _(This message will disappear, once this node revised.)_ When `tar' reads files, this causes them to have the access times updated. To have `tar' attempt to set the access times back to what they were before they were read, use the `--atime-preserve' option. Handling of file attributes `--atime-preserve' Preserve access times on files that are read. This doesn't work for files that you don't own, unless you're root, and it doesn't interact with incremental dumps nicely (Note: Backups), and it can set access or modification times incorrectly if other programs access the file while `tar' is running; but it is good enough for some purposes. `-m' `--touch' Do not extract file modified time. When this option is used, `tar' leaves the modification times of the files it extracts as the time when the files were extracted, instead of setting it to the time recorded in the archive. This option is meaningless with `--list' (`-t'). `--same-owner' Create extracted files with the same ownership they have in the archive. This is the default behavior for the superuser, so this option is meaningful only for non-root users, when `tar' is executed on those systems able to give files away. This is considered as a security flaw by many people, at least because it makes quite difficult to correctly account users for the disk space they occupy. Also, the `suid' or `sgid' attributes of files are easily and silently lost when files are given away. When writing an archive, `tar' writes the user id and user name separately. If it can't find a user name (because the user id is not in `/etc/passwd'), then it does not write one. When restoring, and doing a `chmod' like when you use `--same-permissions' (`--preserve-permissions', `-p'), it tries to look the name (if one was written) up in `/etc/passwd'. If it fails, then it uses the user id stored in the archive instead. `--no-same-owner' Do not attempt to restore ownership when extracting. This is the default behavior for ordinary users, so this option has an effect only for the superuser. `--numeric-owner' The `--numeric-owner' option allows (ANSI) archives to be written without user/group name information or such information to be ignored when extracting. It effectively disables the generation and/or use of user/group name information. This option forces extraction using the numeric ids from the archive, ignoring the names. This is useful in certain circumstances, when restoring a backup from an emergency floppy with different passwd/group files for example. It is otherwise impossible to extract files with the right ownerships if the password file in use during the extraction does not match the one belonging to the filesystem(s) being extracted. This occurs, for example, if you are restoring your files after a major crash and had booted from an emergency floppy with no password file or put your disk into another machine to do the restore. The numeric ids are _always_ saved into `tar' archives. The identifying names are added at create time when provided by the system, unless `--old-archive' (`-o') is used. Numeric ids could be used when moving archives between a collection of machines using a centralized management for attribution of numeric ids to users and groups. This is often made through using the NIS capabilities. When making a `tar' file for distribution to other sites, it is sometimes cleaner to use a single owner for all files in the distribution, and nicer to specify the write permission bits of the files as stored in the archive independently of their actual value on the file system. The way to prepare a clean distribution is usually to have some Makefile rule creating a directory, copying all needed files in that directory, then setting ownership and permissions as wanted (there are a lot of possible schemes), and only then making a `tar' archive out of this directory, before cleaning everything out. Of course, we could add a lot of options to GNU `tar' for fine tuning permissions and ownership. This is not the good way, I think. GNU `tar' is already crowded with options and moreover, the approach just explained gives you a great deal of control already. `-p' `--same-permissions' `--preserve-permissions' Extract all protection information. This option causes `tar' to set the modes (access permissions) of extracted files exactly as recorded in the archive. If this option is not used, the current `umask' setting limits the permissions on extracted files. This option is meaningless with `--list' (`-t'). `--preserve' Same as both `--same-permissions' (`--preserve-permissions', `-p') and `--same-order' (`--preserve-order', `-s'). The `--preserve' option has no equivalent short option name. It is equivalent to `--same-permissions' (`--preserve-permissions', `-p') plus `--same-order' (`--preserve-order', `-s'). automatically generated by info2www version 1.2.2.9 |