obtar -g

Purpose

Use obtar -g to create backup images for the directories and files specified in the backup description file. obtar automatically creates a volume label (-z option), updates the backup dates files, and generates an index file (-G option).

Syntax

obtar -g::=

obtar -g backup-description-file
[ -f devicename ]
[ -F { cur | end | file-number } ]
[ -L backup-level ] 
[ -lR ] [ -v [ -v ] ] [ -z ]

Semantics

You can specify a number of options with obtar -g; this section describes those options that you are most likely to use. Refer to "obtar Options" for information about additional obtar -g options.

-g backup-description-file

Specifies the path name of the backup description file (BDF). If you specify a host name as part of the backup description file name, as in -g brhost:/work/mybdf, then the Oracle Secure Backup client software must be installed on this host. If you specify a relative path name for the backup description file, then obtar looks for it with respect to the current directory.

In addition to data, obtar records each of the path names specified in the BDF as part of the backup image. When you restore that data, obtar uses this path name as the location for the restored data. The obtar -x command, which you use to restore data, provides options that let you specify a different host or directory location for the restored data.

By default, obtar -g does not cross local or remote mount points. You can override this behavior by using mount point statements in a BDF (see "Mount Point Statement") or specifying the -Xcrossmp option.

obtar issues a warning if the contents of a file change during a backup of the file.

-f devicename

Specifies the name of a backup device created with the mkdev command. If you do not specify -f, then obtar writes to the device specified by the TAPE environment variable, if it is defined.

-F { cur | end | file-number }

If you specify cur, then obtar writes the backup image at the current volume position. cur is the default if you do not specify the -F option.

If you specify end, then obtar writes the new backup image immediately after the last existing backup image on the volume set. Use this option when the last backup image was written completely. (If obtar failed with a media error while writing the last backup image, then -F end will produce undesirable results.)

If you specify file-number, then obtar writes the backup image at the specified file position. obtar numbers each of the backup images on a volume beginning with 1. When you specify -F 1, obtar writes the backup image at the beginning of the volume. If you specify a number greater than 1, then at least file-number - 1 backup images must already exist on the volume.

-L backup-level

Specifies a backup level. If you omit this option, then obtar performs a full backup.

-l

Forces obtar not to cross file system mount points when backing up or restoring. Note that if you also specify -Xchkmnttab, then specifying -l causes obtar to consult the mount table (/etc/mnttab) to avoid crossing remote mount points.

-R

Runs obtar with root access. To use -R you must be a member of a class with the perform restores as privileged user right. You do not need to use -R if you are logged in as root.

-v [ -v ]

Displays the backup image label and the path names of files and directories being backed up. If you specify -v -v (or -vv),then obtar displays the backup image label as well as the path names, permissions, owner, size, and date of last modification of the files and directories being backed up.

-z

Displays the label of the backup image.

Examples

Creating a Backup Image on a Volume

The command in Example 4-5 uses the BDF named all_bdf to create a backup image at the current tape position on the volume loaded on the device tape1.

obtar -g all_bdf -f tape1

Using a Remote BDF

The command in Example 4-6 creates a backup image using the BDF named rd_bdf located on the host named hershey. Note that hershey must have Oracle Secure Backup installed.

obtar -g hershey:/admin/bdf/rd_bdf -f tape1

Creating a Full Backup

The command in Example 4-7 specifies that obtar should perform a full backup of the data specified in the BDF called all_bdf. The -R option indicates that the command should run with root privileges.

obtar -g all_bdf -f tape2 -L full -R

Creating an Incremental Backup

The command in Example 4-8 specifies that obtar should perform an incremental backup on that same data shown in Example 4-7.

obtar -g all_bdf -f tape2 -L incr -R

Displaying Information About the Backup Image

Example 4-9 uses -v to display information about the data being backed up. obtar displays the backup image's volume label as well as the path names of the data being backed up.

obtar -g first_bdf -f tape1 -v

Backup started on Wed Nov 09 2005 at 14:57:42
Volume label:
    Volume ID:          VOL000009
    Volume sequence:    1
    Volume set owner:   root
    Volume set created: Tue Nov 08 14:54:32 2005
 
Archive label:
    File number:        4
    File section:       1
    Owner:              lashdown
    Client host:        dlsun1976
    Backup level:       0
    S/w compression:    no
    Archive created:    Wed Nov 09 14:57:42 2005
 
Dumping all files in /tmp
/tmp/
/tmp/.X11-pipe/
/tmp/.X11-pipe/X0
...
/tmp/smc898/
/tmp/smc898/boot.pid
 
Backup complete on Wed Nov 09 2005 at 14:58:01

Controlling Mount Point Behavior

Assume that the path /usr/dir1 contains a number of symbolic link files that point to files on a remote file system. For example, /usr/dir1/linkfile is a symbolic link to /usr/dir2/data-file, and /usr/dir2 is an NFS mount point.

Assume that you create a BDF named /tmp/example.bdf with the following syntax:

+/usr/dir1

You specify the -h option, which indicates that obtar should back up the data pointed to by the symbolic links, in the obtar -g statement shown in Example 4-10.

obtar -g /tmp/example.bdf -f vt1 -h

In Example 4-10, obtar will not back up the data pointed to by /usr/dir1/linkfile because by default obtar will not cross the /usr/dir2 mount point. Thus, the data in /usr/dir2/data-file will not be backed up.

Assume that you alter the BDF so that it uses the following syntax:

+/usr/dir1
@crossremotemountpoints

You re-run the command shown in Example 4-10. In this case, obtar will back up the data pointed to by /usr/dir1/linkfile because the BDF directs obtar to cross remote mount points in the /usr/dir1 file system. Because /usr/dir1/linkfile points to /usr/dir2/data-file, and /usr/dir2 mounts a remote file system, the data in /usr/dir2/data-file will be backed up.

Now assume that you specify -h along with -l, which forces obtar not to cross mount points regardless of other mount point options, in the obtar -g statement shown in Example 4-11.

obtar -g /tmp/example.bdf -f vt1 -h -l

In Example 4-11, obtar backs up the symbolic link files but not the files to which the links point to. This behavior results because the -l option overrides the @crossremotemountpoints statement in the BDF.

Restricting Backups to a File System

If your file system includes local or NFS mounts points, then obtar ordinarily backs up any data that it can access through them. You can use the obtar -l option to prevent obtar from crossing mount points. For example, suppose the top-level directory of the host chicago is mounted on the /home directory of the host boston. Your BDF specifies that all data in boston's /home directory should be backed up. In Example 4-12, obtar backs up all the data in boston's /home directory as well as all the data on chicago.

obtar -g home_bdf -f tape1 -R 

If you include the -l option, as shown in Example 4-13, then obtar backs up only the data in boston's /home directory.

obtar -g home_bdf -f tape1 -R -l 

If you explicitly specify an NFS mount point in a BDF, then obtar backs up the data specified by that mount point whether you have used -l or not.

Specifying a Backup Image Location with -F

When you are creating a backup image on a volume, obtar ordinarily begins writing the backup image in the volume's current position. In some circumstances you may want to specify explicitly where obtar should begin writing a new backup image. For example, suppose the backup fails, leaving the volume positioned in the middle of an unreadable backup image. When you redo the backup, you would want to specify that obtar begin writing before the unreadable backup image.

You can use the -F option to cause obtar to write a backup image in a specified location. The command in Example 4-14 writes the backup image as backup image 3.

obtar -g all_bdf -f tape1 -F 3

When obtar creates a backup image at a specified volume position, the new backup image becomes the last backup image, even if the volume previously contained additional backup images. For example, if 11 backup images existed previously, and if you write backup image number 3, then you effectively erase images 4 through 11. If you use -F cur (or omit the option altogether), and if the volume is positioned at the beginning, then obtar writes the new backup image as file 1 of a new volume, regardless of whether previous data is on the volume.

When you are using a volume set and specify -F end or -F file-number, obtar first positions the volume at the requested file within the volume set. If the file is on a volume different from the one currently loaded, then obtar prompts you to make any required volume changes.