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This section covers some advanced considerations in archiving files. You do not need to understand this information in order to use Tivoli Storage Manager for basic work.
When you archive a file, Tivoli Storage Manager saves standard UNIX access permissions assigned to the file. Depending on your operating system, it also saves extended permissions. For example, for files on an AIX workstation, Tivoli Storage Manager saves access control lists.
If you are a user, and you archive a file to which you have read access, you own the archived copy of the file. You are the only user who can retrieve the archived file unless you grant access to another user.
When you archive a symbolic link, Tivoli Storage Manager archives the file to which the symbolic link points. It does not archive path information for the directory.
If you archive a symbolic link that points to a directory, Tivoli Storage Manager archives the files contained in the directory (and its subdirectories if the subdir option is set to yes) under the name of the symbolic link.
Use the archsymlinkasfile option to specify whether Tivoli Storage Manager archives the symbolic link and the file or directory it points to, or the symbolic link only. See Archsymlinkasfile for more information.
The following table shows symbolic link archive and retrieve functions and
the action taken:
Table 15. Symbolic Link Management Table for Archive and Retrieve
Function | Action Taken |
---|---|
Archive of a file link. | Archives the file to which the symbolic link points. |
Archive of a directory link. | Archives the directory and its contents. |
Archive of a file with subdir=yes. | Archives the directory, its contents, and contents of subdirectories. |
Archive of a directory with subdir=yes. | Archives the directory, its contents, and contents of subdirectories. |
Archive of a symbolic link that points to a file or directory that does not exist. | Archives the symbolic link. |
Retrieve a symbolic link that points to file; the file and link exist. | Replaces the file if replace=y is set. |
Retrieve a symbolic link that points to file; the symbolic link no longer exists. | Retrieves the file replacing the file name with the symbolic link name and places it in the directory where the symbolic link resided. |
Retrieve a symbolic link that points to a directory; the symbolic link and directory no longer exist. | A directory is created in the directory where the symbolic link resides, and all files and subdirectories are restored to that directory. The symbolic link name is used as the new directory name. |
Retrieve a symbolic link that points to a directory; the symbolic link and directory still exist. | Tivoli Storage Manager will not retrieve as long as the symbolic link exists. |
When you archive a file that is hard linked to another file, Tivoli Storage Manager stores both the link information and the data file on the server.
When you retrieve a hard linked file, Tivoli Storage Manager attempts to re-establish its links. For example, if you had a hard linked pair of files, and only one of the hard-linked files was on your workstation, when you retrieve both files, they will be hard-linked together.
The one exception to this procedure occurs if you archive two files that are hard-linked together and then break the connection between them on your workstation. The two files then contain separate data files. If you retrieve the two files from the server, Tivoli Storage Manager respects the current file system and does not restore the hard link.
Problems can occur if you back up only one file of a set of hard-linked files. For example, files texta and textb are hard linked to each other. You archive texta, then edit textb and make some changes. If you retrieve texta, the changes you made to textb will be lost.
To ensure that hard-linked files remain synchronized, always archive all hard links at the same time and restore those same files together.