Saving Data With bru

Saving Data With bru

With bru, it is a simple matter to estimate the space a backup requires, back up filesystems or individual directories and files, and compress backups as described in this section.

Note: XFS and bru: The -K option has been added to the bru command for use with files larger than 2 GB. If the -K option is not used, bru skips any files that it cannot compress to less than 2 GB and issues a warning. Note that use of this option can create bru archives that are not usable on non-XFS systems. The -K option can only be used in combination with the -Z (use 12-bit LZW file compression) option.

Estimating Space Required for Backup

Use the -e option with bru for an estimate of how much space is required for an archive, for example:

bru -e /usr

returns how much space is required for the /usr filesystem backup.

Backing Up a Filesystem With bru

The bru command is the shell command used by the System Manager to create backups. If you are using a server and do not have access to the graphical System Manager, use bru instead. Backups made with bru are readable by the System Maintenance Menu and Command Monitor. This command backs up the /usr filesystem:

bru -c /usr

Backing Up Files With bru

To back up individual files with bru, enter:

bru -c files

You can specify one or more files. You can also read filenames from another file:

bru -c - < listfile

where the file listfile is a list of file names to be backed-up.

Saving Files by Modification Date

To save specific files that have changed since a particular time, you can use bru with the -n option. The following command backs up files on the /usr filesystem that have been modified on or after November 26, 1990:

bru -c -n 26-Nov-90 /usr

Saving Files Using Data Compression

You can compress files as they are archived. Use the -Z flag:

bru -Z /usr

bru uses a 12-bit LZW file compression algorithm. Note that not all versions of bru support LZW compression. If you plan to transfer a bru archive to another vendor's workstation, make sure the other version of bru supports LZW data compression.

If you add the -v option, bru displays the compression ratio for each file (as a percentage). If you use -t and -Z to display the table of contents of an archive that contains compressed files, bru displays the current file names and compressed sizes, instead of the original filenames and sizes before creating the archive.

Incremental Backups With bru

You can use the incremental option bru to create incremental backups. For example:

Create a complete backup of the /usr filesystem:
bru -c
Each day, back up the files that have changed since the previous daily backup:
bru -c -n 25-Nov-95 /usr
bru -c -n 26-Nov-95 /usr
bru -c -n 27-Nov-95 /usr
bru -c -n 28-Nov-95 /usr
bru -c -n 29-Nov-95 /usr
bru -c -n 30-Nov-95 /usr
bru -c -n 1-Dec-95 /usr
Every week, back up the files that have changed since the last weekly backup:
bru -c -n 25-Nov-95 /usr
Note that the dates listed in the command examples above are place holders. Use appropriate current dates in your command lines.
At the end of four weeks, perform a complete backup and start the process over.

This is a common incremental backup scheme.