When running CORBA remote objects in a NAT environment (assuming Internet protocols are used), the IIOP IOR remote object references that will be created (and registered at some nameservice) will contain the private IP address (to convince yourself: dump the IOR as string and paste that string in http://www2.parc.com/istl/projects/ILU/parseIOR/). As a result, when a client outside the NAT environment looks up the IOR, it will get one containing the private IP and access to the remote object does of course not work. For the Oracle OpenJDK CORBA implementation, the following command line parameter needs to be provided to both the ORB and the JVM running at the remote object side:
-ORBServerHost PublicIPofServer

Concerning the ports:
By default, the Oracle OpenJDK is using TCP port 1049 for the activation service. You can change this port via the ORB command line parameter -port.

The port used for the CORBA Naming Service (which is automatically provided by the OpenJDK Java ORB) depends on whether orbd is started as root or as an ordinary user: when started as root, TCP port 900 is used, otherwise TCP port 1049 (because ports lower than 1024 can only be created by root). Unfortunately, TCP port 1049 is also used by the activation service as described above. Hence, a port collision (=exceptions) will occur (what a stupid design)!
In this case, let the ORB start the Naming Service e.g. on TCP port 1050:
orbd -ORBInitialPort 1050

When changing the Naming Service port from the default 900, client and server JVMs that use that Naming Service also need to know about the changed Naming Service port number: Start the JVMs with additional parameter:
java -ORBInitialPort 1050

When running client and server on different hosts, take care that they use the same Naming Service. Assuming that the Naming Service running on the server's host is used: the server will anyway use this local Naming Service, but the client needs to know the hostname of the server's Naming Service: start the client JVM with additional parameter:
java -ORBInitialHost nameserverhost

Note that in addition to these standard services (Activation and Naming), CORBA uses by default dynamically assigned TCP ports (=expect difficulties with firewalls) for all further objects such as your own remote objects that are contained in the IORs. However, you can enforce a port to be used by a servant created within a JVM using the additional parameter:
java -ORBServerPort port

Sometimes, students that are not registered for a course (but have an UGLA account), need access to course material in UGLA. This can be achieved as follows:

1. Operations -> Users and groups
2. New group
3. Give the new group some name, e.g. External access. Confirm. (UGLA allows to select registered students to be added here, but leave the group empty!)
4. On the group overview page click on the newly created group.
5. Add user
6. In the SSI/kennitala field: either enter kennitala or the person's full HÍ email address. Save.
7. All operations -> Change group permission. Change permissions accordingly. NOTE: giving permissions for a folder does not recursively apply to the file contained in the folder -- you need to change each and every individual file as well!
8. Using the URL that you get from "Front Page" link (or simply via the link provided in the course catalogue), the persons should be able to access the folder.

Alternatively, in the Files and Folder area, you can for individual files and folders change the access permissions using the Edit/pen symbol -> Access Permissions

If you have a person without UGLA account, the only possibility is to make the whole course page world-wide visible:

1. All Operations -> Change front page title -> At Access to the Teaching Web, select Open for everybody (no authentication)

This and other things (e.g. electronic homework submissing incl. student view of this) is also explained (in Icelandic) at Kennslumiðstöð.

While the CDK5 homepage lists some errata, I found more that are listed below (I reported them, however they did not make it into the official errata):

Table in Figure 3.23: Lower bound of 3G phone bandwidth is 0.384 Mbps, not 384 Mbps. As an update: 4G currently is up to 300 Mbps and has latencies as low as 5 ms.

The table in Figure 3.23 is at least outdated if not wrong, e.g. 10Base5 is only about the 500 m STP; the "T" standards are about twisted pair cables, hence listing coaxial cable (STP) lengths there makes no sense. 1000BaseT allows nowadays 100m twisted pair cables. The "fibre" lines refer rather ot the "F" standards not "T" as the column headings suggest. Furthermore, mono-mode fibre length for 1000BaseF has made significant advancements. Finally, 10GBase, 40GBase and 100GBase are now available.

Further errata to come...

What I did to install Debian Linux (Jessie) on Thinkpad X250:

Booting from USB device (to install Debian) was some challenge: in particular USB 3 needed to be disabled in BIOS (maybe some more BIOS tweaks that I cannot remember anymore).

To make the Trackpoint keys work:

In BIOS, disable Touchpad (anyway a good idea to prevent accidental touches there).

Added file /etc/modprobe.d/x250.conf with content
options psmouse proto=imps

Added file /usr/share/X11/xorg.conf.d/20-thinkpad.conf with content (works only if Touchpad is disabled in BIOS)

Section "InputClass"
Identifier "Trackpoint Wheel Emulation"
MatchProduct "PPS/2 IBM TrackPoint|DualPoint Stick|Synaptics Inc. Composite TouchPad / TrackPoint|ThinkPad USB Keyboard with TrackPoint|USB Trackpoint pointing device|Composite TouchPad / TrackPoint|PS/2 Synaptics TouchPad"
MatchDevicePath "/dev/input/event*"
Option "EmulateWheel" "true"
Option "EmulateWheelButton" "2"
Option "Emulate3Buttons" "false"
Option "XAxisMapping" "6 7"
Option "YAxisMapping" "4 5"
EndSection


Also to make side button of my Logitech USB mouse act as middle button:
Added file 20-logitech-mouse-side-button.conf with content

Section "InputClass"
Identifier "Logitech mouse side button remap"
MatchProduct "Logitech USB Receiver"
MatchDevicePath "/dev/input/event*"
Option "ButtonMapping" "1 0 3 4 5 6 7 2 9 10"
EndSection


(Still sometimes Logitech mouse stops completely to work, then unplugging USB receiver from docking station works -- still need to investigate that. Update it seems that plugging in the USB receiver into another USB port (=other USB type) helps.)

I also experience sometimes that my external Dell monitor connected via DP cable and my dock sometimes blanks for half a second: a firmware update of the dock is needed, but is only available as MS Windows executable. Any hints welcome how to do this via Linux! (A BIOS update via Linux is possible and worked.)
I do not have that problem when using the DVI-D port and cable of the dock -- however for 4k resolution, DP is better than DVI!

I also had an old 1440x900 display that did not report its native resolution when connected via VGA (which btw. reports as DP2). While I might probably add some modeline to some xconfig file as I last did probably 10 years ago, I did the following:

cvt 1440 900
Then pasted the modeline generated by cvt:
xrandr --output DP2 --newmode "1440x900_60.00" 106.50 1440 1528 1672 1904 900 903 909 934 -hsync +vsync
xrandr --addmode DP2 "1440x900"
xrandr --output DP2 --mode 1440x900


Also my other display sometimes gets no recognised:

cvt 1920 1080
Then pasted the modeline generated by cvt:
xrandr --output DP2 --newmode "1920x1080_60.00" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync
xrandr --addmode DP2 "1920x1080"
xrandr --output DP2 --mode 1920x1080

For getting cloned display output with KDE "Display and Monitor" configuration system setting pane, the two screens have to dragged onto each other. However, I like
the old "Size & Orientation" pane more which can be obtained by installing the kde-workspace-randr package.

Just as reminder for me: to use Gutenprint for the photoprinter: create first in CUPS (e.g. via web interface) an entry for the photoprinter so that the printer gets an own queue. Then, in Gimp, this queue can be used when setting up the photoprinter there. In case the Print with Gutenprint menu entry does not show up in Gimp, an extra package needs to be installed: IIRC for Debian it is package: gimp-gutenprint
What I did to install Debian Linux (Jessie) on Thinkpad X250:

Booting from USB device (to install Debian) was some challenge: in particular USB 3 needed to be disabled in BIOS (maybe some more BIOS tweaks that I cannot remember anymore).

To make the Trackpoint keys work:

In BIOS, disable Touchpad (anyway a good idea to prevent accidental touches there).

Added file /etc/modprobe.d/x250.conf with content
options psmouse proto=imps

Added file /usr/share/X11/xorg.conf.d/20-thinkpad.conf with content (works only if Touchpad is disabled in BIOS)

Section "InputClass"
Identifier "Trackpoint Wheel Emulation"
MatchProduct "PPS/2 IBM TrackPoint|DualPoint Stick|Synaptics Inc. Composite TouchPad / TrackPoint|ThinkPad USB Keyboard with TrackPoint|USB Trackpoint pointing device|Composite TouchPad / TrackPoint|PS/2 Synaptics TouchPad"
MatchDevicePath "/dev/input/event*"
Option "EmulateWheel" "true"
Option "EmulateWheelButton" "2"
Option "Emulate3Buttons" "false"
Option "XAxisMapping" "6 7"
Option "YAxisMapping" "4 5"
EndSection


Also to make side button of my Logitech USB mouse act as middle button:
Added file 20-logitech-mouse-side-button.conf with content

Section "InputClass"
Identifier "Logitech mouse side button remap"
MatchProduct "Logitech USB Receiver"
MatchDevicePath "/dev/input/event*"
Option "ButtonMapping" "1 0 3 4 5 6 7 2 9 10"
EndSection


(Still sometimes Logitech mouse stops completely to work, then unplugging USB receiver from docking station works -- still need to investigate that. Update it seems that plugging in the USB receiver into another USB port (=other USB type) helps.)

I also experience sometimes that my external Dell monitor connected via DP cable and my dock sometimes blanks for half a second: a firmware update of the dock is needed, but is only available as MS Windows executable. Any hints welcome how to do this via Linux! (A BIOS update via Linux is possible and worked.)
I do not have that problem when using the DVI-D port and cable of the dock -- however for 4k resolution, DP is better than DVI!

I also had an old 1440x900 display that did not report its native resolution when connected via VGA (which btw. reports as DP2). While I might probably add some modeline to some xconfig file as I last did probably 10 years ago, I did the following:

cvt 1440 900
Then pasted the modeline generated by cvt:
xrandr --output DP2 --newmode "1440x900_60.00" 106.50 1440 1528 1672 1904 900 903 909 934 -hsync +vsync
xrandr --addmode DP2 "1440x900"
xrandr --output DP2 --mode 1440x900


Also my other display sometimes gets no recognised:

cvt 1920 1080
Then pasted the modeline generated by cvt:
xrandr --output DP2 --newmode "1920x1080_60.00" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync
xrandr --addmode DP2 "1920x1080"
xrandr --output DP2 --mode 1920x1080

For getting cloned display output with KDE "Display and Monitor" configuration system setting pane, the two screens have to dragged onto each other. However, I like
the old "Size & Orientation" pane more which can be obtained by installing the kde-workspace-randr package.

Just as reminder for me: to use Gutenprint for the photoprinter: create first in CUPS (e.g. via web interface) an entry for the photoprinter so that the printer gets an own queue. Then, in Gimp, this queue can be used when setting up the photoprinter there. In case the Print with Gutenprint menu entry does not show up in Gimp, an extra package needs to be installed: IIRC for Debian it is package: gimp-gutenprint

Update 27.5.2024: With Debian Bookworm, I can in the CUPS web interface not detect the photoprinter. Install the package printer-driver-gutenprint did make the printer show in the CUPS administrator interface.

But then, I got an error message about an incorrect paper format. I then compiled the latest version of Gutenprint manually -- but this did not compile the Gimp plugin, so I had to install first libgimp2.0-dev.

Still, that did not work, so I had to downgrade the packages to the Gutenprint version prior to the regression:


The issue is resolved by removing these packages and manually installing the packages from Jammy:

libgutenprint-common/jammy,jammy,now 5.3.3-9 all
libgutenprint9/jammy,now 5.3.3-9 amd64
printer-driver-gutenprint/jammy,now 5.3.3-9


For version pinning, create a file in etc/apt/preferences.d with contents:


Package: libgutenprint-common
Pin: version 5.3.3-5
Pin-Priority: 1000
Explanation: Newer versions in Debian have a regression https://sourceforge.net/p/gimp-print/discussion/4359/thread/8fca54c027/

Package: printer-driver-gutenprint
Pin: version 5.3.3-5
Pin-Priority: 1000
Explanation: Newer versions in Debian have a regression https://sourceforge.net/p/gimp-print/discussion/4359/thread/8fca54c027/


Once Debian has versions as new as 5.3.4-2023-08-23 (e.g. in sid), these packages can be used.

RICOH driversy
When I tried to install some Ricoh printer-specifc PPDs (offered by CUPS), that gave an error: