Objektorientierung als Wissenstransfer

Ich mache mir recht viele Gedanken darüber, welche Struktur meine Anwendungen haben sollen. Weil in Quellcode soviel Arbeit steckt wird einmal geschriebener Code immer weiter gereicht, manchmal über 3 oder 4 Teams hinweg, die nichts voneinander wissen. Damit der Wissenstransfer trotzdem funktioniert muss der Quellcode verständlich sein. Im folgenden Beitrag soll das Konzept der Objektorientierung anhand eines Negativbeispiels erklärt werden. Ich versichere Ihnen, dass ich mir dieses Beispiel nicht ausgedacht habe.

Wenn darum geht Dinge aus der tatsächlichen Welt „in den Computer zu bringen“, d.h. ein Modell dieser Dinge zu bauen, dann sind für mich Programmiersprachen die von vornherein mit Blick auf das Konzept der Objektorientierung geschrieben wurden und eine statische Typisierung bieten die erste Wahl.

Nehmen wir zwei Arten von IDs. Die eine Art von IDs benennt ein Team, die andere einen Raum oder ein Gebäude. Beide lassen sich semantisch nicht unterscheiden, d.h. ich kann eine ID von jeder Art aufschreiben und beide können gleich sein. Technisch gesehen sind beide Arten von IDs übrigens Zeichenketten (Strings).

Einer der Fehler, den ich selbst gesehen habe: Beide Arten von IDs wurden in einer Anwendung als Zeichenketten herumgereicht. Weil sie technisch gesehen nichts weiter als Zeichenketten zu sein scheinen. Nun gab es in der Software eine Funktion, die ein Team anhand anderer Merkmale als der ID finden konnte. Was aber wenn kein Team gefunden wurde? Dann gab die Funktion „nichts“ (null) zurück.

Als dies in der Anwendung zu Fehlern führte (NullPointerException), wurde die Funktion so geändert, dass versucht wurde anhand der Suchkriterien den Raum zu finden in dem sich das Team aufhielt. In diesem Fall wurde dann statt der Team-ID die Raum-ID zurückgegeben. Das war möglich denn die Funktion gab ja nur eine Zeichenkette zurück.

Früher oder später wird diese Änderung natürlich zu Verwirrung und Fehlern führen. Wie gesagt ich kann anhand der ID nicht sehen, ob es sich um eine Team-ID oder Raum-ID handelt. Es wird viel Geld kosten um das wieder zu richten.

Wenn sich zwei Menschen über IDs unterhalten, dann wissen wir ja welche Art gemeint ist, entweder aus dem Kontext des Gespräches oder sie verständigen sich ausdrücklich darüber („Sprechen wir über eine Team- oder eine Raum-ID?“). Aber der Computer weiß das nicht! Noch schlimmer: Nicht eingeweihte Entwickler wissen es auch nicht!

Wir geben also unser Menschen-Wissen in den Computer ein indem wir für beide Arten von IDs je eine Klasse zu erstellen:
A. TeamID
B. EstateID (für Grundstücke, Räume, usw.)

Beide Klassen scheinen nichts gemeinsam zu haben, oder doch? Beide sind doch IDs nicht wahr? Welches Verhalten haben IDS gemeinsam?

IDs können normalerweise validiert werden. Daher haben sie eine Definition von Validität – sie können valide sein oder nicht. Ich würde jetzt ein Interface namens AnyID hinzufügen und diesem die Methode isValid(): boolean mitgeben. Jetzt haben IDs etwas gemeinsam: Sie sind validierbar. Und wissen jetzt nicht nur Sie und ich sondern auch alle anderen Entwickler Bescheid!

Die Validierbarkeit von Objekten ist überall dort lebenswichtig, wo Objete über Systemgrenzen weiter gereicht werden. Jedes System muss sicher stellen, dass sie eingegebenen Daten valide sind, damit der Versucht sie zu verarbeiten nicht mit einem undefinierten Zustand endet. (Eine leere ID? – Hilfe!!!)

Nun können AnyID weitere Gemeinsamkeiten hinzugefügt werden. Bitte nur solche, die auch wirklich allen IDs gemeinsam sind. Möglich ist es auch, isValid: boolean in ein neues Interface zu verschieben das allen validierbaren Objekten zu eigen gemacht werden kann. Wenn nun AnyID aber gar keine Methoden mehr hat, dann gibt es keine Gemeinsamkeiten zwischen beiden IDs! Und dann muss AnyID weg! Un dann weiß wieder jeder Entwickler Bescheid, dass IDs eben keine Gemeinsamkeiten haben.

Zum Lesen:
[1] Ralf Westphal: OOP as have you meant it, JavaSpektrum 3/2015
Dieser Artikel hat mich vor schlimmen Fehlern bezüglich der Objektorierung bewahrt und mich dazu gebracht mehr von Alan Kay zu lesen.

Alan Kay gilt als derjenige, den den Begriff „Objektorientierung“ geprägt hat. Hier sind seine Gedanken dazu – und was Objektorientierung seiner Meinung nach eben nicht ist:
[2] http://c2.com/cgi/wiki?AlanKaysDefinitionOfObjectOriented
[3] http://userpage.fu-berlin.de/~ram/pub/pub_jf47ht81Ht/doc_kay_oop_en

Auf dieser Seite beschäftigt sich jemand sehr gründlich mit dem Lebenswerk und den Gedanken Alan Kays an sich:
[4] http://mythz.servicestack.net/blog/2013/02/27/the-deep-insights-of-alan-kay/

 

Werbeanzeigen

Wolfgang von Heese

Recently I created some website for the Artist Wolfgang von Heese, living in Berlin. Now I need a link to main page to cause Google to display the site in the searchlist.

Fedora 16: How to diable boot splash screen?

Fedora 16: How to diable boot splash screen?

attempt #1: removing all packages found by „plymouth“ with „gpk application / Package Manager for GNOME“ => fail boot splash screen still appears.

attempt #2: edit kernel command line options, remove „rhgb“:

$ sudo vi /etc/default/grub

GRUB_CMDLINE_LINUX=“rd.md=0 rd.dm=0 rd.lvm.lv=vg_sommer/lv_root  KEYTABLE=de quiet rd.lvm.lv=vg_sommer/lv_swap rhgb rd.luks.uuid=luks-***** SYSFONT=latarcyrheb-sun16 LANG=en_US.UTF-8″

GRUB_CMDLINE_LINUX=“rd.md=0 rd.dm=0 rd.lvm.lv=vg_sommer/lv_root  KEYTABLE=de quiet rd.lvm.lv=vg_sommer/lv_swap rd.luks.uuid=luks-***** SYSFONT=latarcyrheb-sun16 LANG=en_US.UTF-8″

$ grub2-mkconfig -o /boot/grub2/grub.cfg

=> This leads to success!

edit: replaced hdd id with *****

=-=-=-=-=
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A fool issue with Swing / Open JDK 1.6

A fool issue with Swing / Open JDK 1.6
current package (Fedora 16): java-1.6.0-openjdk-devel-1:1.6.0.0-65.1.11.1.fc16 (64-bit)

My application [1] uses a class which handles the data (storing + calculation) [2], a JTable the present it and a JTableModel to connect data and JTable: JTable -> JTableModel -> data class. When removing a data set the application tells the JTableModel which calls the data class to remove the data set and runs the fireTableRowsDeleted(…) method to tell the JTable to remove the corresponding row.

This works fine if there is no cell in the edit mode. Otherwise – if a cell is in the edit mode – an exception (java.lang.IndexOutOfBoundsException) thrown from JTableModel telling that the JTableModel tries to read an index at data class which does not exist. I.e.: data class has 3 items (0..2) the removing item 2 raises the exception „java.lang.IndexOutOfBoundsException: Index: 2, Size: 2“ while the data class has now two items and JTable has now 2 rows => JTable and data class removed the items as it should but JTable did not recognize the change. A similar issue appeared when adding rows. Adding / removing columns is not a problem in my application because my application because adding or removing columns is allowed only in a JTable which can not be edited but if your application permits it the same problem would occur.

The solution was to kick all cells out of edit mode by running the JTable.editingCanceled(ChangeEvent) method for the JTable object i.e. („table“ = JTable object): „table.editingCanceled(new ChangeEvent(table));“ before removing or adding items.

[1] http://sourceforge.net/projects/jdecisiontable
[2] http://sourceforge.net/projects/jdtlib/

Linux on laptop: Fedora 16 on Asus A54C

 Install Fedora 16 on an ASUS A54C notebook

Build-In hardware overview

Hardware overview taken from manufacturers description or Windows 7 hardware info (this one in „“):

Vendor: ASUSTeK Computer Inc.

Model: A54C-SO325V, version K54C

Display: 15″ NON-GLARE, resolution 1366×768, LED-Backlight

Battery: The battery is quite tall. I don’t know the capacity but my Dell Latitude E4300 has a bigger battery and I knew this is a 6-cell battery.

CPU: Intel B940 (2 x 2,0 Ghz)

RAM: 4 GB / 1333 MHz

Mainboard chipset: „Systemdevices“: „Intel(R) HM65 Express Chipset Family LPC Interface Controller – 1C49“ + „Intel(R) 82802 Firmwarehub“

Graphic chipset: „Intel(R) HD Graphics Family“

Sound: „Audio-, Video- und Gamecontroller“: „Intel(R) Display-Audio“ + „Realtek High Definition Audio“, on the case is „ALTEC Lansing“

USB: USB 3.0 is available says the sticker on the notebook. The left hand USB port has a blue plastic part inside, the right hand port a black one. Left port = USB 3.0 and right port = USB 2.0? Windows 7 tells: „USB-Controller“: „Intel(R) 6 Series/C200 Series Chipset Family USB Enhanced Host Controller – 1C26“

Ethernet adapter: „Atheros AR8151 PCI-E Gigabit Ethernet Controller (NDIS 6.20)“

WLAN: „Atheros AR9285 Wireless Network Adapter“

Hdd: Windows 7 tells only the Device Model thus here is more info by Linux/GSmartControl: Model Family = Seagate Momentus 5400.6, Device Model = ST9320325AS (same as Windows 7 tells), capacity 320 GB

DVD-RW drive: „TSSTcorp CDDVDW SN-208BB“

SD-Card drive: I don’t know.

Mouse: „Synaptics PS/2 Port TouchPad“

Webcam: „ASUS USB2.0 WebCam“

OS: sold with pre-installed Windows 7

Price: 379 EURO (Germany April 2012)

Additional hardware tested here:

 – usb surf stick (usb device for UMTS connection): „XS Stick (r) W14 / http://www.4g-systems.com“ (there is „klarmobil.de“ printed on it)

Notebook

This machine is not made for shining but for working. I use it mainly for developing and office. It has a NON-GLARE display. Even the case and the frame around the display are „non-glare“. The display provides a bright, sharp picture and text is good to read even if some sunlight is shining on it. Usually I turn down brightness. The case is made of black plastic with a surface which comes with a texture so that it is not smooth („it has grip“). The case is stable. Touch pad buttons are of black plastic (also not smooth) which make an audible click sound when hitting it. This sound could annoying people around you. Mouse clicks can be – with Fedora 16 – send only by this buttons. Think twice before using it in the „Ruhebereich“ at Deutsche Bahn :-) The fan is audible when I use the nootebook in silent room but not when there is other noise e.g. in a office. The keys on keyboard has some space between – good for typing. „Delete“ key is above backspace key and „End“ (go to end of line) key is in the upper right corner. The arrow keys (move up-down-right-left) are far away from page-up and page-down.

Size: The size of screen and case is suitable for work in the ICE-trains of Deutsche Bahn (= German Railways).

Operation System

First i installed and run the pre-installed OS to see if all components are working. Everything was fine. Windows 7 (without additional software) runs fast und boots quickly. Then I tried a Fedora 16 live system because an article in the press (c’t 2011, Heft 20, Thorsten Leemhuis: „Arbeitspinguine“ used Fedora and Ubuntu to test some laptops and found that Fedora has better results). It worked fine especially the x-Window system worked fine. The whole screen was used to display. Then I installed Debian testing snapshot (dated by Debian to be of 2012-04-23). I toggled the XFCE desktop to install and the „expert mode“. After install the system booted only into text login. Command „startx“ seems to lock the termial but no X-Windows system appeared. (Did I make a mistake during install?) I logged in on another terminal and shut the system down. The I rebooted Fedora 16 live demo again. It worked fine and due lack of time to try other options I installed it. After installing I found all the hardware listed above working perfectly even webcam and microphone.

Build-In hardware test

Function keys like making screen brighter/darker, sound louder/quieter, switch wireless network devices on/off: works.

Touch pad: Scrolling by moving the finger on right border doesnt work but gestures works! To scroll just put one finger on touch pad and move another finger up-/down or legft/right. Mouseclicks works only by touch pad buttons which produce a noticeable „click!“-noise when hit. This could annoy other people next to you.

Battery: The manufaturers says the laptop should run about 3 hours. Running XFCE4 with reduced display brightness let it run out of power after 2 h. No tweeks were made. My Dell Latitude E6400 with 13″ Screen has a bigger (6-cell) battery and runs 4.5 hours with XFCE + debian testing (coming Debian 7). Compared to screen size (15″ vs. 13″) and prize the 2 hours seems a good deal for me.

The battery applet works. Runtime seems to depend very on screen brightness. Loading the battery while the notbook is running (with reduced screen brightness) takes about 1.5 hours.

Hdd: The hard disk runs quiet. I can’t hear any noise from it. There was no „click-clack“ noise with default settings. The Advanced Power Management was set to 128. (As I understood it this value came from hard disk and Linux is not in duty to change it.) The value of „193: Load / Unload Cycle“ reached 1000 in about 24 hours running (value of „9: Power-On Time“). The 24 h splits in running 22 h on AC and 2 h running on battery. Its about 42 Load / Unload Cycles per hour. This means a runtime of about 14286 hours until reaching the value of 600k which some people see as being maximal number of Load / Unload Cycles which most hard disks can reach before get broken. Assuming that you are using your laptop 10 h per day and 360 days in a year that would mean you can use it about 4 years. Basing on this calculation there seems to be no danger that this hard disk running Fedora 16 will die prematurely when using Linux. „Linux User“ 2012-01 „Bund fürs Leben“ page 66 ff. provides an article about it. There is an easy way to turn the power management less aggressive. I will describe it for Fedora 16 in the next article on this blog.

Usb surf stick: The usb surf stick works out-of-the-box. When the usb surf stick is sticking on left usb port I need to remove it before power-off the notebook since I the notebook reboots instead going power-off. When the reboot finished the system runs stable. When power-off it reboots again running stable after reboot! I tried same with this usb surf stick sticking in the right usb port: When I select power-off the notebook is going power-off. Another issue with this usb surf stick: When first trying it didn’t work. I found the reason to be as the SIM Card wasn’t sticking deep enough in the stick. I used a knife to push it deeper into the device. Then it started working.

External VGA connector (analog): Very good result on a flatscreen @ 1920×1080.

SD-card drive: Tried 16 GB SD-card: Worked out-of-the-box.

Sound: Internal speakers and external headphones are working. Internal speakers are off when external headphones are plugged in.

Hardware info, generated by lshw

(Please understand that i replaced any personal inforamtion like serial numbers by „*****“)

—

sommer

    description: Notebook

    product: K54C ()

    vendor: ASUSTeK Computer Inc.

    version: 1.0

    serial: *****

    width: 64 bits

    capabilities: smbios-2.6 dmi-2.6 vsyscall32

    configuration: boot=normal chassis=notebook family=K uuid=*****

  *-core

       description: Motherboard

       product: K54C

       vendor: ASUSTeK Computer Inc.

       physical id: 0

       version: 1.0

       serial: *****

       slot: MIDDLE

     *-firmware

          description: BIOS

          vendor: American Megatrends Inc.

          physical id: 0

          version: K54C.203

          date: 01/02/2012

          size: 64KiB

          capacity: 2496KiB

          capabilities: pci upgrade shadowing cdboot bootselect edd int13floppy1200 int13floppy720 int13floppy2880 int5printscreen int9keyboard int14serial int17printer acpi usb smartbattery biosbootspecification

     *-cpu

          description: CPU

          product: Intel(R) Pentium(R) CPU B940 @ 2.00GHz

          vendor: Intel Corp.

          physical id: 4

          bus info: cpu@0

          version: Intel(R) Pentium(R) CPU B940 @ 2.00GHz

          serial: To Be Filled By O.E.M.

          slot: CPU 1

          size: 2GHz

          capacity: 4GHz

          width: 64 bits

          clock: 100MHz

          capabilities: x86-64 fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx rdtscp constant_tsc arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl est tm2 ssse3 cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic popcnt tsc_deadline_timer xsave lahf_lm arat epb xsaveopt pln pts cpufreq

          configuration: cores=2 enabledcores=1

        *-cache

             description: L1 cache

             physical id: 5

             slot: L1-Cache

             size: 32KiB

             capacity: 32KiB

             capabilities: internal write-back instruction

     *-memory

          description: System Memory

          physical id: 3f

          slot: System board or motherboard

          size: 4GiB

        *-bank:0

             description: SODIMM DDR3 Synchronous 1333 MHz (0.8 ns)

             product: EBJ41UF8BCS0-DJ-F

             vendor: Elpida

             physical id: 0

             serial: 00000000

             slot: ChannelA-DIMM0

             size: 4GiB

             width: 64 bits

             clock: 1333MHz (0.8ns)

        *-bank:1

             description: DIMM [empty]

             product: [Empty]

             vendor: [Empty]

             physical id: 1

             serial: [Empty]

             slot: ChannelB-DIMM0

     *-pci

          description: Host bridge

          product: 2nd Generation Core Processor Family DRAM Controller

          vendor: Intel Corporation

          physical id: 100

          bus info: pci@0000:00:00.0

          version: 09

          width: 32 bits

          clock: 33MHz

          configuration: driver=agpgart-intel

          resources: irq:0

        *-display

             description: VGA compatible controller

             product: 2nd Generation Core Processor Family Integrated Graphics Controller

             vendor: Intel Corporation

             physical id: 2

             bus info: pci@0000:00:02.0

             version: 09

             width: 64 bits

             clock: 33MHz

             capabilities: msi pm vga_controller bus_master cap_list rom

             configuration: driver=i915 latency=0

             resources: irq:48 memory:dd000000-dd3fffff memory:c0000000-cfffffff ioport:e000(size=64)

        *-communication UNCLAIMED

             description: Communication controller

             product: 6 Series/C200 Series Chipset Family MEI Controller #1

             vendor: Intel Corporation

             physical id: 16

             bus info: pci@0000:00:16.0

             version: 04

             width: 64 bits

             clock: 33MHz

             capabilities: pm msi bus_master cap_list

             configuration: latency=0

             resources: memory:dfc0b000-dfc0b00f

        *-usb:0

             description: USB Controller

             product: 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #2

             vendor: Intel Corporation

             physical id: 1a

             bus info: pci@0000:00:1a.0

             version: 05

             width: 32 bits

             clock: 33MHz

             capabilities: pm debug ehci bus_master cap_list

             configuration: driver=ehci_hcd latency=0

             resources: irq:16 memory:dfc08000-dfc083ff

        *-multimedia

             description: Audio device

             product: 6 Series/C200 Series Chipset Family High Definition Audio Controller

             vendor: Intel Corporation

             physical id: 1b

             bus info: pci@0000:00:1b.0

             version: 05

             width: 64 bits

             clock: 33MHz

             capabilities: pm msi pciexpress bus_master cap_list

             configuration: driver=snd_hda_intel latency=0

             resources: irq:49 memory:dfc00000-dfc03fff

        *-pci:0

             description: PCI bridge

             product: 6 Series/C200 Series Chipset Family PCI Express Root Port 1

             vendor: Intel Corporation

             physical id: 1c

             bus info: pci@0000:00:1c.0

             version: b5

             width: 32 bits

             clock: 33MHz

             capabilities: pci pciexpress msi pm normal_decode bus_master cap_list

             configuration: driver=pcieport

             resources: irq:40 ioport:d000(size=4096) memory:df200000-dfbfffff ioport:d2100000(size=10485760)

        *-pci:1

             description: PCI bridge

             product: 6 Series/C200 Series Chipset Family PCI Express Root Port 2

             vendor: Intel Corporation

             physical id: 1c.1

             bus info: pci@0000:00:1c.1

             version: b5

             width: 32 bits

             clock: 33MHz

             capabilities: pci pciexpress msi pm normal_decode bus_master cap_list

             configuration: driver=pcieport

             resources: irq:41 ioport:c000(size=4096) memory:de800000-df1fffff ioport:d1600000(size=10485760)

           *-network

                description: Wireless interface

                product: AR9285 Wireless Network Adapter (PCI-Express)

                vendor: Atheros Communications Inc.

                physical id: 0

                bus info: pci@0000:02:00.0

                logical name: wlan0

                version: 01

                serial: *****

                width: 64 bits

                clock: 33MHz

                capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless

                configuration: broadcast=yes driver=ath9k driverversion=3.3.2-6.fc16.x86_64 firmware=N/A latency=0 link=no multicast=yes wireless=IEEE 802.11bgn

                resources: irq:17 memory:de800000-de80ffff

        *-pci:2

             description: PCI bridge

             product: 6 Series/C200 Series Chipset Family PCI Express Root Port 4

             vendor: Intel Corporation

             physical id: 1c.3

             bus info: pci@0000:00:1c.3

             version: b5

             width: 32 bits

             clock: 33MHz

             capabilities: pci pciexpress msi pm normal_decode bus_master cap_list

             configuration: driver=pcieport

             resources: irq:42 ioport:b000(size=4096) memory:dde00000-de7fffff ioport:d0b00000(size=10485760)

           *-usb

                description: USB Controller

                product: ASM1042 SuperSpeed USB Host Controller

                vendor: ASMedia Technology Inc.

                physical id: 0

                bus info: pci@0000:03:00.0

                version: 00

                width: 64 bits

                clock: 33MHz

                capabilities: msi msix pm pciexpress xhci bus_master cap_list

                configuration: driver=xhci_hcd latency=0

                resources: irq:19 memory:dde00000-dde07fff

        *-pci:3

             description: PCI bridge

             product: 6 Series/C200 Series Chipset Family PCI Express Root Port 6

             vendor: Intel Corporation

             physical id: 1c.5

             bus info: pci@0000:00:1c.5

             version: b5

             width: 32 bits

             clock: 33MHz

             capabilities: pci pciexpress msi pm normal_decode bus_master cap_list

             configuration: driver=pcieport

             resources: irq:43 ioport:a000(size=4096) memory:dd400000-dddfffff ioport:d0000000(size=10485760)

           *-network

                description: Ethernet interface

                product: AR8151 v2.0 Gigabit Ethernet

                vendor: Atheros Communications

                physical id: 0

                bus info: pci@0000:04:00.0

                logical name: p5p1

                version: c0

                serial: *****

                capacity: 1Gbit/s

                width: 64 bits

                clock: 33MHz

                capabilities: pm msi pciexpress vpd bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation

                configuration: autonegotiation=on broadcast=yes driver=atl1c driverversion=1.0.1.0-NAPI latency=0 link=no multicast=yes port=twisted pair

                resources: irq:50 memory:dd400000-dd43ffff ioport:a000(size=128)

        *-usb:1

             description: USB Controller

             product: 6 Series/C200 Series Chipset Family USB Enhanced Host Controller #1

             vendor: Intel Corporation

             physical id: 1d

             bus info: pci@0000:00:1d.0

             version: 05

             width: 32 bits

             clock: 33MHz

             capabilities: pm debug ehci bus_master cap_list

             configuration: driver=ehci_hcd latency=0

             resources: irq:23 memory:dfc07000-dfc073ff

        *-isa

             description: ISA bridge

             product: HM65 Express Chipset Family LPC Controller

             vendor: Intel Corporation

             physical id: 1f

             bus info: pci@0000:00:1f.0

             version: 05

             width: 32 bits

             clock: 33MHz

             capabilities: isa bus_master cap_list

             configuration: latency=0

        *-storage

             description: SATA controller

             product: 6 Series/C200 Series Chipset Family 6 port SATA AHCI Controller

             vendor: Intel Corporation

             physical id: 1f.2

             bus info: pci@0000:00:1f.2

             version: 05

             width: 32 bits

             clock: 66MHz

             capabilities: storage msi pm ahci_1.0 bus_master cap_list

             configuration: driver=ahci latency=0

             resources: irq:44 ioport:e0b0(size=8) ioport:e0a0(size=4) ioport:e090(size=8) ioport:e080(size=4) ioport:e060(size=32) memory:dfc06000-dfc067ff

        *-serial UNCLAIMED

             description: SMBus

             product: 6 Series/C200 Series Chipset Family SMBus Controller

             vendor: Intel Corporation

             physical id: 1f.3

             bus info: pci@0000:00:1f.3

             version: 05

             width: 64 bits

             clock: 33MHz

             configuration: latency=0

             resources: memory:dfc05000-dfc050ff ioport:e040(size=32)

     *-scsi:0

          physical id: 1

          logical name: scsi0

          capabilities: emulated

        *-disk

             description: ATA Disk

             product: ST9320325AS

             vendor: Seagate

             physical id: 0.0.0

             bus info: scsi@0:0.0.0

             logical name: /dev/sda

             version: 0003

             serial: *****

             size: 298GiB (320GB)

             capabilities: partitioned partitioned:dos

             configuration: ansiversion=5 sectorsize=512 signature=e3102a4b

           *-volume:0

                description: Windows FAT volume

                vendor: MSDOS5.0

                physical id: 1

                bus info: scsi@0:0.0.0,1

                logical name: /dev/sda1

                version: FAT32

                serial: *****

                size: 24GiB

                capacity: 25GiB

                capabilities: primary hidden fat initialized

                configuration: FATs=2 filesystem=fat

           *-volume:1

                description: EXT4 volume

                vendor: Linux

                physical id: 2

                bus info: scsi@0:0.0.0,2

                logical name: /dev/sda2

                logical name: /boot

                version: 1.0

                serial: *****

                size: 500MiB

                capacity: 500MiB

                capabilities: primary bootable journaled extended_attributes huge_files dir_nlink recover extents ext4 ext2 initialized

                configuration: created=2012-05-01 06:05:26 filesystem=ext4 lastmountpoint=/boot modified=2012-05-02 17:18:41 mount.fstype=ext4 mount.options=rw,seclabel,relatime,user_xattr,acl,barrier=1,data=ordered mounted=2012-05-02 17:18:41 state=mounted

           *-volume:2

                description: Linux filesystem partition

                physical id: 3

                bus info: scsi@0:0.0.0,3

                logical name: /dev/sda3

                serial: *****

                size: 272GiB

                capacity: 272GiB

                width: 512 bits

                capabilities: primary encrypted luks initialized

                configuration: bits=512 cipher=aes filesystem=luks hash=sha1 mode=xts-plain64 version=1

     *-scsi:1

          physical id: 2

          logical name: scsi1

          capabilities: emulated

        *-cdrom

             description: DVD-RAM writer

             product: CDDVDW SN-208BB

             vendor: TSSTcorp

             physical id: 0.0.0

             bus info: scsi@1:0.0.0

             logical name: /dev/cdrom1

             logical name: /dev/cdrw1

             logical name: /dev/dvd1

             logical name: /dev/dvdrw1

             logical name: /dev/scd0

             logical name: /dev/sr0

             version: AS01

             capabilities: removable audio cd-r cd-rw dvd dvd-r dvd-ram

             configuration: ansiversion=5 status=nodisc

—

Germany, May 2012

=-=-=-=-=
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Linux on laptop: Debian 6 (stable branch) and 7 (testing branch) on a Dell Latitude E4300

Build-In hardware overview

Manufacturer: Dell

Type: Latitude E4300, purchased 2009 via telephone from Germany

Processors: 

Memory: 4 GB

Mainboard: 

Graphics: 

Sound: 

WLAN: 

Harddisk: 250 GB capacity

DVD: („DVD+Rewriteable“)

Display type: 13″ Non-glare

Bios: 

other: SD-Card drive

Battery: 6-cell

Weight with battery: 1492 gramm, without battery > 1000 gramm

Notebook

This notebook is a light-weight high-end notebook. Of course it was expensive. But I travel a lot and I wanted to get rid of the bigger and heavier Toshiba A100-589 (reported earlier in this blog) AND I wanted a high-end machine to work quickly with Windows.

WHY I WOULDN’T BUY IT AGAIN: Mine seem to have a hardware fault. It was delivered with Windows Vista Ultimate SP1 (90 € extra to pay). With this the system freezed from time to time as we know from Windows 9x. I (this was an error) blamed Windows Vista for the freezes and deleted it in favour of Linux after I sucessfully tested Linux about 3 months. Later Linux started also from time to time esp. when watching flash movies with Adobe(R) Flash(R). Now I blamed Adobe Adobe(R) Flash(R) and this was wrong again. I realised that crashes occurs when the system asked for extra power. I called Dell service. After changing the whole mainboard no freezes happend! Sorry Microsoft + Adobe, that I blamed your software. It was an error. I didn’t buy an warranty enhancement thinking the issue were fixed – after time of warranty was over the system started to freeze again. I found a feature in the BIOS named „Intel speed step“ and disabled it because I observed the freezing when the system need extra power. This fixed it – almost (two freezes in 8 months). I always used the Ext4 file system with encrypted home directory (ecryptfs) which always protected my data (truecrypt drives among it). I found no file damaged or lost. MANY THANKS the people who made the Ext4 file system!!! Because of the descripted behavior this notebook was replaced by a Asus A54C (also reported in this blog). After there is no need for running Windows because I am happy with Linux I feel no need for such a high-end machine. For Linux and what I am doing with it (developing and office) a low-end machine is good enough.

Operation System

I installed Debian 6 „Sequeeze“ stable, updated it and switched then to the testing branch of upcoming Debian 7 „Wheezy“ (both 64 bit). Earlier I had Ubuntu 8.10 – 10.04 (32 bit) on it but this is not the scope of this report.

Build-In hardware test

Keyboard, mousepad, USB: Works out of the box. Localisation is de_DE_UTF8 (I selected german localisation). Pressing „Y“-key prints an „Y“ not „Z“. Can type Euro-Sign €, |, @, \, ÄÖÜäöüß (AOUaou-umlaut + sharp s). Mouse moves, mousekeys works, (after changing the configuration through the graphical program which come whith Gnome for this purpose) double-hitting the mousepad works also. Can connect and disconnect USB-devices.

Network:  Ethernet + WLAN works out of the box. Internal USB-modem needed use of wvdial for Ubuntu 8.10 only, later I could do out of the box with Gnome’s and KDE’s graphical network managers.

Graphics: Resolution of built-in screen is 1280×800. This laptop comes with an external VGA-connector (analog). Connecting it to a Flatscreen it shows a very useable view. I had resolutions up to 1920×1080 on Ubuntu.

Sound: Works out of the box, very good. Even the volume-control shortcuts on keyboard works.

DVD: Can burn DVDs even video DVDs.

SD-Card drive: Works fine (read/write).

ACPI: Fan runs only short from time to time. If the machine has to work harder, the fan starts running (in two steps) but stops running withinsome time after work load is done. The machine did never overheat.

Battery: It runs 4.5 hour while developing (writing, compiling, running).

Hardware info, generated by lshw

(Please understand that i replaced any personal inforamtion like serial numbers by „*****“)

—

slingshot

    description: Portable Computer

    product: Latitude E4300 ()

    vendor: Winbond Electronics

    serial: *****

    width: 64 bits

    capabilities: smbios-2.4 dmi-2.4 vsyscall32

    configuration: boot=normal chassis=portable uuid=*****

  *-core

       description: Motherboard

       vendor: Winbond Electronics

       physical id: 0

       serial: .*****.              .

     *-firmware

          description: BIOS

          vendor: Winbond Electronics

          physical id: 0

          version: A21

          date: 01/11/2011

          size: 64KiB

          capacity: 1664KiB

          capabilities: isa pci pcmcia pnp upgrade shadowing cdboot bootselect int13floppy720 int5printscreen int9keyboard int14serial int17printer int10video acpi usb agp smartbattery biosbootspecification netboot

     *-cpu

          description: CPU

          product: Intel(R) Core(TM)2 Duo CPU     P9400  @ 2.40GHz

          vendor: Intel Corp.

          physical id: 400

          bus info: cpu@0

          slot: Microprocessor

          size: 1600MHz

          capacity: 2400MHz

          width: 64 bits

          clock: 266MHz

          capabilities: x86-64 fpu fpu_exception wp vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx constant_tsc arch_perfmon pebs bts rep_good nopl aperfmperf pni dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm sse4_1 xsave lahf_lm tpr_shadow vnmi flexpriority

          configuration: cores=2 enabledcores=2 threads=2

        *-cache:0

             description: L1 cache

             physical id: 700

             size: 128KiB

             capacity: 128KiB

             capabilities: internal write-back data

        *-cache:1

             description: L2 cache

             physical id: 701

             size: 6MiB

             capacity: 6MiB

             clock: 66MHz (15.0ns)

             capabilities: pipeline-burst internal varies unified

     *-memory

          description: System Memory

          physical id: 1000

          slot: System board or motherboard

          size: 4GiB

        *-bank:0

             description: DIMM DDR3 Synchronous 1066 MHz (0,9 ns)

             product: HMT125S6TFR8C-G7

             vendor: Hynix Semiconductor (Hyundai Electronics)

             physical id: 0

             serial: *****

             slot: DIMM_A

             size: 2GiB

             width: 64 bits

             clock: 1066MHz (0.9ns)

        *-bank:1

             description: DIMM DDR3 Synchronous 1066 MHz (0,9 ns)

             product: 16JSF25664HZ-1G1F1

             vendor: Micron Technology

             physical id: 1

             serial: *****

             slot: DIMM_B

             size: 2GiB

             width: 64 bits

             clock: 1066MHz (0.9ns)

     *-pci

          description: Host bridge

          product: Mobile 4 Series Chipset Memory Controller Hub

          vendor: Intel Corporation

          physical id: 100

          bus info: pci@0000:00:00.0

          version: 07

          width: 32 bits

          clock: 33MHz

          configuration: driver=agpgart-intel

          resources: irq:0

        *-display:0

             description: VGA compatible controller

             product: Mobile 4 Series Chipset Integrated Graphics Controller

             vendor: Intel Corporation

             physical id: 2

             bus info: pci@0000:00:02.0

             version: 07

             width: 64 bits

             clock: 33MHz

             capabilities: msi pm vga_controller bus_master cap_list rom

             configuration: driver=i915 latency=0

             resources: irq:47 memory:f6c00000-f6ffffff memory:e0000000-efffffff ioport:ef70(size=8)

        *-display:1 UNCLAIMED

             description: Display controller

             product: Mobile 4 Series Chipset Integrated Graphics Controller

             vendor: Intel Corporation

             physical id: 2.1

             bus info: pci@0000:00:02.1

             version: 07

             width: 64 bits

             clock: 33MHz

             capabilities: pm bus_master cap_list

             configuration: latency=0

             resources: memory:f6b00000-f6bfffff

        *-communication:0 UNCLAIMED

             description: Communication controller

             product: Mobile 4 Series Chipset MEI Controller

             vendor: Intel Corporation

             physical id: 3

             bus info: pci@0000:00:03.0

             version: 07

             width: 64 bits

             clock: 33MHz

             capabilities: pm msi bus_master cap_list

             configuration: latency=0

             resources: memory:f6ad9ef0-f6ad9eff

        *-ide

             description: IDE interface

             product: Mobile 4 Series Chipset PT IDER Controller

             vendor: Intel Corporation

             physical id: 3.2

             bus info: pci@0000:00:03.2

             version: 07

             width: 32 bits

             clock: 66MHz

             capabilities: ide pm msi bus_master cap_list

             configuration: driver=ata_generic latency=0

             resources: irq:18 ioport:ef78(size=8) ioport:ef68(size=4) ioport:ef80(size=8) ioport:ef6c(size=4) ioport:ef90(size=16)

        *-communication:1

             description: Serial controller

             product: Mobile 4 Series Chipset AMT SOL Redirection

             vendor: Intel Corporation

             physical id: 3.3

             bus info: pci@0000:00:03.3

             version: 07

             width: 32 bits

             clock: 66MHz

             capabilities: pm msi 16550 bus_master cap_list

             configuration: driver=serial latency=0

             resources: irq:17 ioport:ef88(size=8) memory:f6ada000-f6adafff

        *-network

             description: Ethernet interface

             product: 82567LM Gigabit Network Connection

             vendor: Intel Corporation

             physical id: 19

             bus info: pci@0000:00:19.0

             logical name: eth0

             version: 03

             serial: 00:21:70:ba:51:fd

             capacity: 1Gbit/s

             width: 32 bits

             clock: 33MHz

             capabilities: pm msi bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation

             configuration: autonegotiation=on broadcast=yes driver=e1000e driverversion=1.5.1-k firmware=1.7-7 latency=0 link=no multicast=yes port=twisted pair

             resources: irq:43 memory:f6ae0000-f6afffff memory:f6adb000-f6adbfff ioport:efe0(size=32)

        *-usb:0

             description: USB controller

             product: 82801I (ICH9 Family) USB UHCI Controller #4

             vendor: Intel Corporation

             physical id: 1a

             bus info: pci@0000:00:1a.0

             version: 03

             width: 32 bits

             clock: 33MHz

             capabilities: uhci bus_master cap_list

             configuration: driver=uhci_hcd latency=0

             resources: irq:20 ioport:6f60(size=32)

        *-usb:1

             description: USB controller

             product: 82801I (ICH9 Family) USB UHCI Controller #5

             vendor: Intel Corporation

             physical id: 1a.1

             bus info: pci@0000:00:1a.1

             version: 03

             width: 32 bits

             clock: 33MHz

             capabilities: uhci bus_master cap_list

             configuration: driver=uhci_hcd latency=0

             resources: irq:21 ioport:6f80(size=32)

        *-usb:2

             description: USB controller

             product: 82801I (ICH9 Family) USB UHCI Controller #6

             vendor: Intel Corporation

             physical id: 1a.2

             bus info: pci@0000:00:1a.2

             version: 03

             width: 32 bits

             clock: 33MHz

             capabilities: uhci bus_master cap_list

             configuration: driver=uhci_hcd latency=0

             resources: irq:22 ioport:6fa0(size=32)

        *-usb:3

             description: USB controller

             product: 82801I (ICH9 Family) USB2 EHCI Controller #2

             vendor: Intel Corporation

             physical id: 1a.7

             bus info: pci@0000:00:1a.7

             version: 03

             width: 32 bits

             clock: 33MHz

             capabilities: pm debug ehci bus_master cap_list

             configuration: driver=ehci_hcd latency=0

             resources: irq:22 memory:fed1c400-fed1c7ff

        *-multimedia

             description: Audio device

             product: 82801I (ICH9 Family) HD Audio Controller

             vendor: Intel Corporation

             physical id: 1b

             bus info: pci@0000:00:1b.0

             version: 03

             width: 64 bits

             clock: 33MHz

             capabilities: pm msi pciexpress bus_master cap_list

             configuration: driver=snd_hda_intel latency=0

             resources: irq:45 memory:f6adc000-f6adffff

        *-pci:0

             description: PCI bridge

             product: 82801I (ICH9 Family) PCI Express Port 1

             vendor: Intel Corporation

             physical id: 1c

             bus info: pci@0000:00:1c.0

             version: 03

             width: 32 bits

             clock: 33MHz

             capabilities: pci pciexpress msi pm normal_decode bus_master cap_list

             configuration: driver=pcieport

             resources: irq:40 ioport:3000(size=4096) memory:f0400000-f05fffff ioport:f0600000(size=2097152)

        *-pci:1

             description: PCI bridge

             product: 82801I (ICH9 Family) PCI Express Port 2

             vendor: Intel Corporation

             physical id: 1c.1

             bus info: pci@0000:00:1c.1

             version: 03

             width: 32 bits

             clock: 33MHz

             capabilities: pci pciexpress msi pm normal_decode bus_master cap_list

             configuration: driver=pcieport

             resources: irq:41 ioport:2000(size=4096) memory:f6900000-f69fffff ioport:f0200000(size=2097152)

           *-network

                description: Wireless interface

                product: Ultimate N WiFi Link 5300

                vendor: Intel Corporation

                physical id: 0

                bus info: pci@0000:0c:00.0

                logical name: wlan0

                version: 00

                serial: *****

                width: 64 bits

                clock: 33MHz

                capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless

                configuration: broadcast=yes driver=iwlwifi driverversion=3.2.0-2-amd64 firmware=8.83.5.1 build 33692 ip=192.168.178.21 latency=0 link=yes multicast=yes wireless=IEEE 802.11abgn

                resources: irq:46 memory:f69fe000-f69fffff

        *-pci:2

             description: PCI bridge

             product: 82801I (ICH9 Family) PCI Express Port 4

             vendor: Intel Corporation

             physical id: 1c.3

             bus info: pci@0000:00:1c.3

             version: 03

             width: 32 bits

             clock: 33MHz

             capabilities: pci pciexpress msi pm normal_decode bus_master cap_list

             configuration: driver=pcieport

             resources: irq:42 ioport:d000(size=4096) memory:f6600000-f68fffff ioport:f0000000(size=2097152)

        *-usb:4

             description: USB controller

             product: 82801I (ICH9 Family) USB UHCI Controller #1

             vendor: Intel Corporation

             physical id: 1d

             bus info: pci@0000:00:1d.0

             version: 03

             width: 32 bits

             clock: 33MHz

             capabilities: uhci bus_master cap_list

             configuration: driver=uhci_hcd latency=0

             resources: irq:20 ioport:6f00(size=32)

        *-usb:5

             description: USB controller

             product: 82801I (ICH9 Family) USB UHCI Controller #2

             vendor: Intel Corporation

             physical id: 1d.1

             bus info: pci@0000:00:1d.1

             version: 03

             width: 32 bits

             clock: 33MHz

             capabilities: uhci bus_master cap_list

             configuration: driver=uhci_hcd latency=0

             resources: irq:21 ioport:6f20(size=32)

        *-usb:6

             description: USB controller

             product: 82801I (ICH9 Family) USB UHCI Controller #3

             vendor: Intel Corporation

             physical id: 1d.2

             bus info: pci@0000:00:1d.2

             version: 03

             width: 32 bits

             clock: 33MHz

             capabilities: uhci bus_master cap_list

             configuration: driver=uhci_hcd latency=0

             resources: irq:22 ioport:6f40(size=32)

        *-usb:7

             description: USB controller

             product: 82801I (ICH9 Family) USB2 EHCI Controller #1

             vendor: Intel Corporation

             physical id: 1d.7

             bus info: pci@0000:00:1d.7

             version: 03

             width: 32 bits

             clock: 33MHz

             capabilities: pm debug ehci bus_master cap_list

             configuration: driver=ehci_hcd latency=0

             resources: irq:20 memory:fed1c000-fed1c3ff

        *-pci:3

             description: PCI bridge

             product: 82801 Mobile PCI Bridge

             vendor: Intel Corporation

             physical id: 1e

             bus info: pci@0000:00:1e.0

             version: 93

             width: 32 bits

             clock: 33MHz

             capabilities: pci subtractive_decode bus_master cap_list

             resources: memory:f6500000-f65fffff

           *-firewire

                description: FireWire (IEEE 1394)

                product: R5C832 IEEE 1394 Controller

                vendor: Ricoh Co Ltd

                physical id: 1

                bus info: pci@0000:02:01.0

                version: 05

                width: 32 bits

                clock: 33MHz

                capabilities: pm ohci bus_master cap_list

                configuration: driver=firewire_ohci latency=64 maxlatency=4 mingnt=2

                resources: irq:19 memory:f65ff800-f65fffff

           *-generic

                description: SD Host controller

                product: R5C822 SD/SDIO/MMC/MS/MSPro Host Adapter

                vendor: Ricoh Co Ltd

                physical id: 1.1

                bus info: pci@0000:02:01.1

                version: 22

                width: 32 bits

                clock: 33MHz

                capabilities: pm bus_master cap_list

                configuration: driver=sdhci-pci latency=64

                resources: irq:18 memory:f65ff600-f65ff6ff

        *-isa

             description: ISA bridge

             product: ICH9M-E LPC Interface Controller

             vendor: Intel Corporation

             physical id: 1f

             bus info: pci@0000:00:1f.0

             version: 03

             width: 32 bits

             clock: 33MHz

             capabilities: isa bus_master cap_list

             configuration: latency=0

        *-storage

             description: SATA controller

             product: 82801IBM/IEM (ICH9M/ICH9M-E) 4 port SATA Controller [AHCI mode]

             vendor: Intel Corporation

             physical id: 1f.2

             bus info: pci@0000:00:1f.2

             logical name: scsi2

             logical name: scsi3

             version: 03

             width: 32 bits

             clock: 66MHz

             capabilities: storage msi pm ahci_1.0 bus_master cap_list emulated

             configuration: driver=ahci latency=0

             resources: irq:44 ioport:6e70(size=8) ioport:6e78(size=4) ioport:6e80(size=8) ioport:6e88(size=4) ioport:6ea0(size=32) memory:fed1c800-fed1cfff

           *-disk

                description: ATA Disk

                product: ST9250421ASG

                vendor: Seagate

                physical id: 0

                bus info: scsi@2:0.0.0

                logical name: /dev/sda

                version: DE14

                serial: *****

                size: 232GiB (250GB)

                capabilities: partitioned partitioned:dos

                configuration: ansiversion=5 signature=0008361d

              *-volume:0

                   description: EXT4 volume

                   vendor: Linux

                   physical id: 1

                   bus info: scsi@2:0.0.0,1

                   logical name: /dev/sda1

                   logical name: /

                   version: 1.0

                   serial: *****

                   size: 229GiB

                   capacity: 229GiB

                   capabilities: primary bootable journaled extended_attributes large_files huge_files dir_nlink recover extents ext4 ext2 initialized

                   configuration: created=2011-06-06 21:54:10 filesystem=ext4 label=linux lastmountpoint=/ modified=2012-04-29 10:42:32 mount.fstype=ext4 mount.options=rw,relatime,errors=remount-ro,user_xattr,acl,barrier=1,data=ordered mounted=2012-05-17 21:19:29 state=mounted

              *-volume:1

                   description: Extended partition

                   physical id: 2

                   bus info: scsi@2:0.0.0,2

                   logical name: /dev/sda2

                   size: 3775MiB

                   capacity: 3775MiB

                   capabilities: primary extended partitioned partitioned:extended

                 *-logicalvolume

                      description: Linux swap / Solaris partition

                      physical id: 5

                      logical name: /dev/sda5

                      capacity: 3775MiB

                      capabilities: nofs

           *-cdrom

                description: DVD-RAM writer

                product: DVD+-RW TS-U633A

                vendor: TSSTcorp

                physical id: 1

                bus info: scsi@3:0.0.0

                logical name: /dev/cdrom

                logical name: /dev/cdrw

                logical name: /dev/dvd

                logical name: /dev/dvdrw

                logical name: /dev/sr0

                version: D200

                capabilities: removable audio cd-r cd-rw dvd dvd-r dvd-ram

                configuration: ansiversion=5 status=nodisc

        *-serial

             description: SMBus

             product: 82801I (ICH9 Family) SMBus Controller

             vendor: Intel Corporation

             physical id: 1f.3

             bus info: pci@0000:00:1f.3

             version: 03

             width: 64 bits

             clock: 33MHz

             configuration: driver=i801_smbus latency=0

             resources: irq:19 memory:f6ad9f00-f6ad9fff ioport:1100(size=32)

  *-battery

       product: DELL FM33889

       vendor: SMP

       physical id: 1

       slot: Sys. Battery Bay

       capacity: 52000mWh

       configuration: voltage=11,1V

  *-network DISABLED

       description: Ethernet interface

       physical id: 2

       logical name: wwan0

       serial: *****

       capabilities: ethernet physical

       configuration: broadcast=yes driver=cdc_ether driverversion=22-Aug-2005 firmware=Mobile Broadband Network Device link=no multicast=yes

—

Germany, May 2012

=-=-=-=-=
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Debian testing: Can’t log in to Xfce – and how to fix this

Last Wednesday I turned on my Laptop and tried to log in to Xfce desktop as usual. But after typing in my password and hitting Enter the system worked a moment and then a saw the window for graphical log in again. For cases like this (or when I like a change) always have a second desktop installed (LXDE). I could log in using LXDE without problems.

With Google I found this Can’t log in to xfce. It says: "Recently I solved this by deleting /~/.ICEauthotity ". OK, I renamed this file in my home directory to _ICEauthotity, made a fresh backup (one but not the only reason is that I use an encrypted file system to protect my data ;-))) and rebooted.

I was able to log in to Xfce again!

What may happened?

.ICEauthority file when I was unable to log in to Xfce (renamed to _ICEauthority):

-rw------- 1 michael michael 0 Mär 28 18:46 _ICEauthority

.ICEauthority file when I was able to log in to Xfce:

-rw------- 1 michael michael 330 Apr 1 16:54 .ICEauthority

The .ICEauthority file was empty!

Conclusion:

1) You may delete the .ICEauthority file – Linux can restore it on next reboot

2) When the .ICEauthority file is empty it may cause trouble like you can not log in to your desktop.

3) It was a good idea to have a second desktop already installed.