Administrator's Guide

• Examine the log file of latest backups to identify problems occurring during backup.
Set restrictive permissions on the backup log file.
• Be aware that the frecover command allows you to overwrite a file. However,
the file retains the permissions and ACLs set when the file was backed up.
• Test the recovery process beforehand to make sure you can fully recover data in the
event of an emergency.
• When recovering files from another machine, you might have to execute the chown
command to set the user ID and group ID for the system on which they now reside,
if the user and group do not exist on the new system. If files are recovered to a new
system that does not have the specified group, the files will take on the group
ownership of the person running the frecover command. If the owner and group
names have different meanings on different systems, recovery results might be
unexpected and not what you wanted.
• Although a power failure should not cause file loss, if someone reports a lost file
after a power failure, look for it in the /lost+found directory before restoring it
from a backup tape.
• To verify contents of the tape being recovered, use the -I option of the frecover
command to preview the index of files on the tape. Existing permissions of a file
system are kept intact by the backup. The frecover command prevents you from
reading the file if the permissions on the file forbid it.
• Never recover in place any critical files, such as /etc/passwd or those in /tcb/
files. Instead, restore the file to a temporary directory (do not use /tmp), and
give this directory permissions drwx------, preventing anyone else from using it.
Compare the restored files with those to be replaced. Make any necessary changes.
• Be sure to turn auditing on. Auditing is not enabled automatically when you have
recovered the system.
1.7 Postinstallation Security Tips for Backup and Recovery 27