| Securing and Optimizing Linux: RedHat Edition -A Hands on Guide | ||
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| Prev | Chapter 22. Software -Server/Mail Network | Next |
Aliasing is the process of converting one local recipient name on the system into another -aliasing occurs only on local names. Example uses are to convert a generic name -such as root, into a real username on the system, or to convert one name into a list of many names -for mailing lists. For every envelope that lists a local user as a recipient, Sendmail looks up that recipient's name in the aliases file. Because Sendmail may have to search through thousands of names in the aliases file, a copy of the file is stored in a separate db database format file to significantly improve lookup speed. If you configure your Sendmail to use a Central Server Mail Hub to handles all mail, you don't need to install the aliases and aliases.db files on the neighbor server or client machines.
Create the aliases file touch /etc/mail/aliases and add the following lines by default:
#
# @(#)aliases 8.2 (Berkeley) 3/5/94
#
# Aliases in this file will NOT be expanded in the header from
# Mail, but WILL be visible over networks or from /bin/mail.
#
# >>>>>>>>>> The program "newaliases" must be run after
# >> NOTE >> this file is updated for any changes to
# >>>>>>>>>> show through to sendmail.
#
# Basic system aliases -- these MUST be present.
MAILER-DAEMON: postmaster
postmaster: root
# General redirections for pseudo accounts.
bin: root
daemon: root
nobody: root
# Person who should get root's mail
#root: admin
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: Your aliases file will be probably far more complex, but even so, note how the example shows the minimum form of aliases.
Since /etc/mail/aliases is a database, after creating the text file as described above, you must use the makemap program to create the database map. To create the aliases database map, use the following command:
[root@deep] /# makemap hash /etc/mail/aliases.db < /etc/mail/aliases
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The
/etc/mail/virtusertable,
domaintable
mailertable
virtusertable.db,
domaintable.db,
mailertable.db
A virtusertable is a database that maps virtual domains into news addresses. With this feature, mail for virtual domain on your network can be delivered to local, remote, or a single user address.
A domaintable is a database that maps old domain to a new one. With this feature, multiple domain names on your network can be rewritten from the old domain to the new.
A mailertable is a database that maps host.domain names to special delivery agent and new domain name pairs. With this feature mail on your network can be delivered through the use of a particular delivery agent to a new local or remote domain name.
To create the virtusertable, domaintable, mailertable, and their corresponding .db files into /etc/mail directory, use the following commands:
[root@deep] /# for map in virtusertable domaintable mailertable
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> do
> touch /etc/mail/${map}
> chmod 0644 /etc/mail/${map}
> makemap hash /etc/mail/${map}.db < /etc/mail/${map}
> chmod 0644 /etc/mail/${map}.db
> done
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