Monitoring a UPS with NUT on Ubuntu Server

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Successfully tested on Ubuntu Server 10.04 LTS 64-bit

Running a Linux server without taking care of possible power failures is not a good idea. A power outage can be disastrous for your valuable data if the server is not connected to an emergency power system, notified of the outage and able to properly shutdown the system while on battery power. With an Ubuntu home server, this kind of situations can be handled using a UPS (Uninterruptible Power Supply) and Network UPS Tools (NUT).

First, install NUT:

apt-get install nut

 
Next, declare your UPS in /etc/nut/ups.conf (I use an MGE Protection Center 675 so don’t forget to modify the driver value according to your own UPS model, as found in NUT documentation):

[ups]
	driver = usbhid-ups
	port = auto
	desc = "MGE UPS SYSTEMS Protection Center 675"

 
In /etc/nut/nut.conf, set NUT daemon to run in standalone mode. It’s the mode to use on the machine to which the UPS is connected and when this same machine also monitors the UPS:

MODE = standalone

 
In /etc/nut/upsd.conf, bind a listening port to the LAN interface if you want to allow other LAN hosts to monitor the UPS through upsd, the UPS network daemon. If not, just keep the first line:

LISTEN 127.0.0.1
LISTEN 192.168.253.2

 
Set the permissions for upsd in /etc/nut/upsd.users. Only the users (one section = one user) listed in this file will be allowed to read the UPS state:

[upsmonitor]
	password = password1
	upsmon master

[monuser]
        password = password2
        upsmon slave

(the [monuser] section is optional and only added here to allow a LAN host to monitor the UPS state over the network)
 
Now, configure the upsmon daemon. Its role is to communicate with upsd to know the UPS status and send specific commands when some events occur. Modify /etc/nut/upsmon.conf as follows:

MONITOR ups@localhost 1 upsmonitor password1 master

 
Finally, make sure to modify the permissions of all NUT configuration files:

chown root:nut /etc/nut/*
chmod 640 /etc/nut/*

 
Now that everything is setup, let see some useful commands.

To start NUT manually (upsd and upsmon daemons simultaneously):

service nut start

 
To check both daemons status:

service nut status

 
To launch the UPS driver:

upsdrvctl start

 
To know the UPS status:

upsc ups

(modify ups according to the section name you used in /etc/nut/ups.conf)
 
To test the server behavior in case of power outage, use the following command:

upsmon -c fsd

 
If the UPS is connected to mains, the server will stop and then restart (don’t forget to set your BIOS power management to “Always on”). If the UPS is unplugged, the server will restart only after reconnection to mains.
 
One last thing: If you have a “BUS= will be removed in a future udev version” error at system boot, see https://bugs.launchpad.net/ubuntu/+source/nut/+bug/692171 for a solution.
 
That’s all Folks!


For further reading, see NUT website.

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Ubuntu Server system administration made easier: Webmin

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Successfully tested on Ubuntu Server 10.04 LTS 64-bit

Tired of being a command-line master? You would like to do Ubuntu Server administration tasks using some kind of GUI? DO NOT install Ubuntu’s desktop environment. Install Webmin instead.

The easiest way to install Webmin on Ubuntu is by using the official Webmin APT repository. First, create a new /etc/apt/sources.list.d/webmin.list file containing the following lines:

## Webmin repository
deb http://download.webmin.com/download/repository sarge contrib
deb http://webmin.mirror.somersettechsolutions.co.uk/repository sarge contrib

 
Next, get the repository GPG key

wget http://www.webmin.com/jcameron-key.asc

 
and add it to your trusted keys list:

apt-key add jcameron-key.asc

 
Finally, resynchronize the list of available packages

apt-get update

 
and install Webmin:

apt-get install webmin

 
Now, you should be able to login to Webmin at https://webmin_server_hostname:10000 using any existing sudoer account and discover the many possibilities of this wonderful tool.

That’s all Folks!


For further reading, see Webmin website.

Installing a network printer with CUPS

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Successfully tested on Ubuntu Server 10.04 LTS 64-bit

Having a network-capable printer greatly ease its installation and everyday use. It can be remotely managed or shared on the local network without having to setup (and keep turned on) a computer as a printer server for instance. It can also be located wherever you wish (especially if you use wireless or PLC networking technologies to connect the printer to the network) and, best of all, it’s very easy to install on Ubuntu Server Edition.

First thing to do is to install CUPS which handles printing on Ubuntu:

apt-get install cups

 
Next, we need to modify its configuration file /etc/cups/cupsd.conf.
Instruct the CUPS server to listen on the LAN interface only (reference to the loopback address can be commented out):

#Listen localhost:631
Listen 192.168.253.2:631

 
Set the authentication and permissions parameters in all the ‹Location› sections to limit access to sudoers only:

AuthType Default
Require user @admin
Order allow,deny
Allow @LOCAL

 
The following option can also be modified if you don’t want CUPS to share (publish) the printer:

DefaultShared no

 
Save the changes and restart CUPS:

service cups restart

 
Now, you can continue the installation using the web interface available at https://cups_server_hostname:631/admin. Just click on the “Add printer” button and follow the instructions. CUPS should automatically find your printer on the network. When asked to enter the printer’s make and model, best would be to provide a PPD file (driver) instead. You can often find this file by extracting the official Windows driver (at least that’s what I’ve done for my Dell 1700n printer).

Once all steps are completed, print a test page:

lpstat -p -d

 
If everything went fine, you should soon hear the printer coming to life.

That’s all Folks!


For further reading, see CUPS website.

Sharing a scanner over the network with Linux

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Successfully tested on Ubuntu Server 10.04 LTS 64-bit

A scanner installed on the server and only accessible locally through the command-line is not very user-friendly. Sharing it over the network to use it from Linux with GUI, Windows or Mac OS X clients would be a great step forward. That’s what we’ll do today.

First, make sure sane-utils is installed by issuing:

apt-show-versions -a sane-utils

 
If not, install it with the apt-get install command.

Then, configure saned, the daemon used to allow remote clients to access the scanner over the network. Modify /etc/default/saned to enable it:

RUN=yes

 
Edit /etc/sane.d/saned.conf and add the following line to restrict access to local subnet hosts only (adapt to your own network configuration):

192.168.253.0/24

 
Restart the daemon

service saned restart

 
and make sure it will start automatically at boot up:

update-rc.d saned defaults

 
Now you should be able to remotely access the scanner on the local network using, for example, SaneTwain on a Windows client. Download and install it following the instructions on the website and you’ll quickly hear the carriage moving and see your first preview image on the screen.

That’s all Folks!


For further reading, see XSane website. It’s an open source graphical scanning frontend which can be installed on multiple platforms and perfectly works with saned.

Installing a scanner on Ubuntu Server Edition

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Successfully tested on Ubuntu Server 10.04 LTS 64-bit

Today’s mission is to install a scanner (EPSON Perfection V200 Photo) which will be used locally on the server. As you’ll see, it’s pretty easy.

Download the driver and other packages specific to the EPSON Perfection V200 Photo scanner at EPSON Support website:

iscan_*.ltdl7_amd64.deb
iscan-data_*_all.deb
iscan-plugin-gt-f670_*_amd64.deb

Install them:

dpkg -i iscan*.deb

 
In case of dependencies errors during the installation, correct them using the following command:

apt-get -f install

 
Verify the presence of the /etc/sane.d/dll.d/iscan file which should contain a single line:

epkowa

 
epkowa is the name of the backend used by SANE to control the scanner. If the iscan file is not there, edit /etc/sane.d/dll.conf and add or uncomment the following line:

epkowa

 
Now set access permissions to the device by creating a new file /etc/udev/rules.d/40-saned.rules with a udev rule which will automatically assign the scanner to the saned group

# Epson Perfection V200 Photo
ATTRS{idVendor}=="04b8", ATTRS{idProduct}=="012e",GROUP="saned"

(ATTRS values can be found using the lsusb command)

and reload the ACL:

udevadm trigger

 
Each local user will have to be added to the saned group before he can access the scanner:

usermod -aG saned username

 
One last modification can also be done to /etc/sane.d/epkowa.conf but it seems not to be mandatory:

usb
#scsi

 
OK, we’re almost done! Let see if we can access the scanner:

sane-find-scanner

 
should return something similar to:

found USB scanner (vendor=0x04b8 [EPSON], product=0x012e [EPSON Scanner]) 
at libusb:002:003

 
Great! Now we can install a command-line frontend named scanimage which is included in the sane-utils package

apt-get install sane-utils

 
and try if it sees the scanner:

scanimage -L

 
If everything went fine, the answer should look like:

device `epkowa:interpreter:002:003' is a Epson Perfection V200 flatbed sca
nner

 
To scan for real, place a document in the scanner and type:

scanimage --format=tiff > test.tif

 
The scan is made using all the default parameters of the device and placed in the current directory.

That’s all Folks!


For further reading, see the SANE project website.

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