CentOS 6.2 + CUPS + AirPrint for iOS

混合環境下的打印方法的選擇。

So we share our printer via IPP using CUPS. What the heck is IPP? It's just printing over HTTP. Why use IPP versus, say, Windows Printer Sharing? Simple: we've got a mixed environment of Windows XP, Windows 7, OS X 10.6, OS X 10.7, Fedora, Ubuntu, and CentOS workstations. IPP is supported by all of them. Plus, I could get AirPrint to work on it, which means you can add iOS in that list of Operating Systems above.

CUPS

So obviously you need to get CUPS to work first.

yum install cups ghostscript usbutils

So there's the cups package, ghostscript, and usbutils. Since most printers these days are connected via USB, it's always nice to have usbutils installed. Ghostscript is needed since most printers don't really support PostScript so I install it just in case.

So once you've got those installed, you need printer drivers. With so many different printer manufacturers, I leave that up to you, dear reader, as to how to install it. You'll usually need a PPD file. NOTE: if you're printer is supported via foomatic or gutenprint, you can install drivers via:

yum install foomatic gutenprint-foomatic

This should install most drivers available. For example, we have an old Samsung ML-1510 that is supported by foomatic. We do have a newer Samsung ML-1860 that isn't. That required me to download and install Samsung's Unified Printer Driver (ugh). Its install script installed a bunch of .desktop files for every account on our server. So I had to search the entire server and remove all of these useless files. To Samsung: sheesh. This also installed an initscript called smfpd, which is a daemon for parallel port printers. Again, sheesh. You can't disable this from startup via chkconfig. There is a commented out "exit 0" near the start. Uncomment that and the daemon should stop running on startup. Make sure you stop the daemon first as it consumes a bit of CPU and memory. Sheesh. Sorry for the semi-rant.

Anyway, the default CUPS configuration only allows access to localhost. Since I don't worry too much about security, and you can secure it after, I change the following in /etc/cupsd.conf:

I add the following:

ServerAlias *
Port 631

which makes the server listen to any hostname (our server has a CNAME to it calling it 'printer01') on port 631.

Then I make sure to change all "Order deny,allow" to "Order allow,deny" and add an "Allow all" to everything after. This way, I can now remotely access the web GUI at:

http://hostname:631/

Change hostname for whatever you call your print server. If at anytime you're asked for a username and password, use your server's root account. So now that you have access to the web GUI, simply add your printer here.

Now you should be able to start CUPS:

service cups start && chkconfig cups on

Test your printer

So you should be able to add your printer to your workstations. The whole URL to your printer is:

http://hostname:631/printers/PRINTERNAME

or:

ipp://hostname/printers/PRINTERNAME

Special note for Mac users: for the "Queue" setting, make sure you include the "printers" portion. So 'Address' would be the hostname. 'Queue' would be "printers/PRINTERNAME".

Once you've added the printer and selected/installed the correct driver, you should be good to go.

If not, there is a setting called 'LogLevel'. By default it's set as follows:

LogLevel warn

Change it to:

LogLevel debug

and monitor the log files in /var/logs/cups/error_log for any problems.

AirPrint

So now for the fun part: getting AirPrint to work so users can print from their iPhones and iPads. There are some great references online, plus a great script to automatically generate the configuration files needed to get your printer advertised by Avahi.

So, Timothy J. Fontaine of Ataraxia Consulting created a python script that automatically generates a .service file for the printers connected via CUPS. You can read hisblog postabout it. The GitHub repository is available here:

https://github.com/tjfontaine/airprint-generate

Anyway, you can (hopefully) download the file directly here:

https://raw.github.com/tjfontaine/airprint-generate/master/airprint-generate.py

First you'll need to install Avahi:

yum install avahi avahi-compat-libdns_sd

Then you need to install the Python cups module. For CentOS 6.2, this is, strangely, in the "system-config-printer-libs" package. So:

yum install system-config-printer-libs

Then you can run the airprint-generate.py script. Copy the generated .service files into /etc/avahi/services. Then you can start the service:

service avahi-daemon start && chkconfig avahi-daemon on

I had some trouble with printers not being advertised. Since my local network is on br1 instead of eth2 (a KVM thing), I had to add the following to /etc/avahi-daemon.conf:

allow-interfaces=br1

If you had to add that, restart avahi-daemon.

And that's it. Printers should start showing up on your iOS devices.