ULINK_ON_OVERWRITE option for NetBackup servers
When a UNIX client indicates Overwrite existing files as a restore option, the UNLINK_ON_OVERWRITE option forces NetBackup to perform the following actions:
The file can be any normal file, symbolic link, hard link, or empty directory.
The addition of UNLINK_ON_OVERWRITE helps minimize potential security and data loss problems from following existing symbolic links. It also guarantees that files are restored exactly as they were backed up.
Table: ULINK_ON_OVERWRITE information
Usage | Description |
|---|
Where to use | On NetBackup primary servers. |
How to use | This option should appear only once in the configuration file.
Restore job performance is reduced by using this option. If the UNLINK_ON_OVERWRITE option is not indicated in the bp.conf file but the option is specified, the behavior of NetBackup is different when it restores symbolic links. (Or, if the option is set to NO.) NetBackup unlinks existing files or empty directories when it restores symbolic links, hard links, or special files (CHR, BLK, and FIFO).
However, NetBackup does not unlink when it restores normal files or directories, which can be problematic. NetBackup follows the symbolic link and creates or replaces the files that the symbolic link points to. Or, it replaces the directory that the symbolic link points to.
SKIP_RESTORE_TO_SYMLINK_DIR and UNLINK_ON_OVERWRITE do not affect each other if both are specified, with one exception:
When the following options are enabled: Then, when a restore job comes across a symbolic link, the link is unlinked before the job checks, and the files and directories are restored. |
Example | For example, if the /home/user/ path was backed up as a directory and, when restored, it is a symbolic link to a directory: With SKIP_RESTORE_TO_SYMLINK_DIR set (and indicated), no files are restored into the directory the symbolic link points to, and the symbolic link remains. With both UNLINK_ON_OVERWRITE and SKIP_RESTORE_TO_SYMLINK_DIR (and indicated), the symbolically linked directory is unlinked, the original directory is restored, and all files within the directory are also restored. With neither set (and indicated), NetBackup follows the symbolic link and restore all files into the directory the symbolic link points to.
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Equivalent Administration Console property | No equivalent exists in the NetBackup Administration Console host properties. |
