Virtual Domains and qmail
If mail for a new user in a virtual domain is to be forwarded to an existing on-site user or to an off-site user, you don't need to create an account for the new user. You can create a .qmail-xxx file in the virtual domain master user's home directory to forward the mail. The master user is the user we created above, who is currently receiving all mail for the virtual domain. For the address firstname.lastname@example.org, you create a file ~abc/.qmail-john:smith, containing the address to which John's mail is to be forwarded in this way:
Note that any periods in the user's Internet name are replaced with colons in the .qmail-xxx file name. The forwarding address which is stored within the .qmail-xxx file does not have periods replaced with colons.
If a user of a virtual domain will be picking up his mail using POP3, you must create an account and an incoming mail directory for him. The POP3 daemon, which comes with qmail, cannot pick up mail from an ordinary mbox formatted file.
# adduser jsmith # chmod g-w ~jsmith # chmod o-w ~jsmith # cd ~jsmith # maildirmake Maildir # chown -R jsmith.users Maildir
The chmod commands in the above script ensure that no one can write to jsmith's home directory except jsmith himself. qmail enforces this requirement as a security measure, but it can be relaxed with a compile-time option—see ALIAS_PATERNALISM in the conf-unusual.h file.
Note that under Linux distributions which include the adduser command, like Slackware, you can do a maildirmake in /etc/skel, so new users will automatically get a Maildir.
As in the previous section, you need to create a .qmail-xxx file in the home directory of the virtual domain's master user to forward mail to each individual user. To forward mail for email@example.com to the local user jsmith we would create a file, ~abc/.qmail-john:smith, containing the line:
To indicate where his incoming mail should be stored, we would create a .qmail file in the home directory for jsmith, containing:
/home/jsmith/Maildir/This step is required because the qmail POP server expects to find a user's mail in a specially constructed directory (the default name of which is Maildir), and we have to tell qmail to put it there.
Once you start storing incoming mail in a nonstandard place, you have to tell the local mail programs where to find it. The standard Linux mail programs cannot read mail from the Maildir format, so qmail includes several wrapper programs to move any incoming mail into mbox format (qail, qine, qlm, for mail, pine and elm respectively). You can rename the real mail user agents and link these wrappers to the usual names, so your users won't even see a difference. These wrappers need a bit of information to operate correctly. To take care of this, add this type of lines to the /etc/profile file:
export MAILDIR=$HOME/Maildir export MAIL=$HOME/Mailbox export MAILTMP=$HOME/Mailbox.tmp
The final thing you have to do is install qmail's POP3 daemon. It is split into three programs, one of which deals with user names and passwords. Those of you with shadow passwords installed will appreciate this modularity. A password checking program, checkpassword, which works with ordinary Linux /etc/passwd files, is available at the same URL as the qmail distribution. The POP3 line in your /etc/inetd.conf will have to be modified. How to do this is described in detail in the FAQ that comes with qmail.
If you feel the above changes are too disruptive, an alternative is to patch your existing POP3 daemon to look for a user's incoming mail in an mbox-formatted file in the user's home directory, rather than a similar file in /var/spool/mail. One such package is available at ftp://summersoft.fay.ar.us/pub/qmail/. The only thing you lose by using a patched POP server rather than the POP server distributed with qmail is the much more reliable Maildir mail storage format.
If you want to forward all mail for a new virtual domain, but you have no reason to create a master user ID for that domain (e.g., you're not providing web services), you can do this using the special alias user ID. Instead of adding the line abc.com:abc to /var/qmail/control/virtualdomains, add the line:
This designates the alias user as the responsible party for all mail to the abc.com domain. qmail's default installation sets the alias user's home directory to /var/qmail/alias, so control of all e-mail for abc.com is done in this directory.
You can create a file ~alias/.qmail-abc-default to forward all mail for abc.com to a specific user. You can also create a series of files, like ~alias/.qmail-abc-webmaster and ~alias/.qmail-abc-john:smith, to forward mail for specific people at abc.com.
Note that the alias user (or any other user) can control mail for multiple virtual domains. To control abc.com and anotherdomain.org, put the following lines in the /var/qmail/control/virtualdomains file:
You'll need these files in the ~alias directory:
~alias/.qmail-abc-john:smith ~alias/.qmail-abc-nancy:jones ~alias/.qmail-abc-webmaster ~alias/.qmail-anotherdomain-sam:adams ~alias/.qmail-anotherdomain-webmasterNote that unlike sendmail, you can have two users with the same Internet user name, as long as they're in different virtual domains. In the above example, there's a firstname.lastname@example.org and a email@example.com.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
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With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide