Ubuntu Remote Release Upgrade Introduction Running a remote release upgrade can be dangerous, VPN, SSH can be updated or break during the upgrade process and leave a not bootable system as a result... This post shows how to mitigate the risks. NOTE…
C# Exception Handling Can I ignore exceptions? No. Exceptions are thrown by the .NET framework in many places, FileNotFoundException, FormatException on conversions, ... A ThreadInterruptedException may occur at any time. On function calls you might…
Mini-DV Cassette How to perform mini DV Grabbing with minimal and quantifiable quality loss. Pitfall: The FireWire interface used to perform grabbing is checking for transfer errors only, not content errors inside the grabbed data. Therefore the…
DNS APIs There is no single API call to perform the lookup. Options are: libc getaddrinfo libc gethostbyname (OBSOLETE SPEC) libc resolver library (Low level DNS retrieval) direct interfacing to the dns servers via network calls The applications that…
Software Design Patterns Taken from Wikipedia, personal adaptations and additions made, shortened to be used as a small reference card, links back to wikipedia kept for details. See also Software Anti-Patterns. Architectural patterns Choice: How is…
Joins (INNER) JOIN The INNER JOIN keyword selects all rows from both the tables as long as the condition satisfies. This keyword will create the result-set by combining all rows from both the tables where the condition satisfies i.e value of the…
ZFS on Linux Installation on ubuntu 20.04 LTS Introduction: https://linuxhint.com/zfs-concepts-and-tutorial/ There are different levels of operation pool level: bundles several virtual devices vdev level: allows to define which redundancy is applied…
Number Theory Links: https://oeis.org/ Definition: Arithmetic Function Functions from the natural numbers to the complex numbers $${ f(n) = c \vert n \in \mathbb{N}, c \in \mathbb{C} }$$ Definition: Multiplicative Function An arithmetic function $f…
MySQL Report table sizes Replace with appropriate value. Find columns Replace , with appropriate values. Performance IN vs EXISTS Change into See https://dev.mysql.com/doc/refman/8.0/en/subquery-optimization-with-exists.html
Nintendo Infos Account passwort ändern (Verlust/Defekt/Diebstahl) Unterschiede Hauptkonsole & nicht Hauptkonsole erklärt Transfer Spiele/Daten zwischen Konsolen Spielestand Speicherung Speicherdaten übertragen Nintendo-Account Ein Nintendo-Account…
Database terms Definitions / Rules Entity <--> Database Table Naming convention: singular, uppercase Instance of an entity <--> Database Row (or Tuple or Record) Attribute <--> Database Column (or Field). Naming convention: singular, lowercase…
DOORS DXL Tips Deactivation of (dangerous) the auto-declaration feature (put it for example in ) Documentation https://www.ibm.com/docs/en/ermd/9.7.2?topic=function-extending-doors-dxl https://www.ibm.com/docs/en/SSYQBZ_9.7.2/com.ibm.doors…
Docker Ubuntu 20.04 setup Install docker Install basic support tools: Configure to restart docker on boot: Install docker-compose Download docker compose and make it executable (here 1.29.2, change accordingly) Check versions Permissions Give…
Borg Introduction Borg is a client server system allowing to backup remotely to repositories Risk analysis Scenario: Backup server compromised Confidentiality of all client data in danger if no encryption is used. Client encryption is a must, could…
Introduction Git-Annex can be used to synchronize bigger files across networks that might not be very reliable or fast. Building git annex 64 bit version under windows Prerequisites cygwin 64 bit: gcc rsync git wget ssh gnupg git for windows 64bit…
Backup script Backup via shell Skript vom host zur NAS. Daten - Backup Wenn die Synology an ist, kann auf dem Backup (Nur Lesend) an diesem zugegriffen werden: \SYNDEHAAN\NetBackup Die Anmeldung erfolg mit dem mitgeteilten Benutzerkonto. Die Daten…
LG TV 2020 Einstellungen fürs TV Anschlüsse: Bild bei https://app.diagrams.net/ erstellt CEC Steuert das automatischen ein und ausschalten wenn man einen anderen Gerät ein oder ausshaltet. Overscan Sorgt dafür dass nichts von den Quelldaten…
GIMP Gimp toolbox They are customizable in the Edit -> Keyboard Shortcuts menu The default shortcuts are presented here (From version 2.6) NR Key Name Type Default Ctrl Shift Alt 01 Rectangular selection Selection Rectangle Center Square 0…
C# Equality vs Identity Reference Microsoft: Guidelines for Overriding Equals() and Operator == Pay attention Equality means the objects have the same value, but are not necessarily the same instance Identity means the objects point to the one and…
Introduction files are VirtualBox native virtual drive containers. These can have a fixed size or be dynamic, consuming as much space as is needed. "Hardware virtualization" deals with how to convert a real partition into a container for use within…
PC Build 2020 Requirements reduce noise (priority 1) reduce power (priority 2) optimized in processing videos code compilation Thoughts Opted for an air cooled 3950X against a water cooled system because of some doubts regarding maintenance and…
Risk analysis: data loss Personal risk analysis and planned countermeasures. Initially I thought it would be a good idea to buy an ECC RAM enabled hardware but this looks like an adventure with consumer hardware. Reliable server component being both…
Radeon 4670 support Problem is a blank screen during and after startup. The BIOS boot logo can be seen correctly. Official Hardware Support ends But the open source driver is available (with some missing features) https://wiki.archlinux.org/index.php…
DIY NAS Requirements support 8 SATA disks support ECC reduce noise (prio 1) reduce power (prio 2) Components Component Price Size(s) Description Mainboard ~300€ uATX SUPERMICRO X10SRM-F Server Motherboard R3 (LGA 2011) Intel C612 Mainboard ~400€ ATX…
Greatest Free and Open Source Software Quite often people hear or use software that is free of charge (freeware). Here I want to present great software that is additionally Open Source. This additional requirement is important to me as I like to have…
Backup solutions Must haves chunk based deduplication) (not only file based) client / server (transfer to remote backup server) web viewer consistency check easy restoration (ro mountable) scriptable and customizable runs on Windows & Linux Nice to…
Ubuntu Tweaks BtrFS maintenance balance tree: weekly scrub: BtrFS snapshot settings https://wiki.archlinux.org/index.php/snapper is managing the snapshots there are a couple of systemd services to trigger snapshots Disable snapshot on boot: Edit to…
Password in domain Password expiration info Renew password With NET USER Using powershell https://docs.microsoft.com/en-us/powershell/module/addsadministration/set-adaccountpassword?view=win10-ps Using smbpasswd (from ) Fix trust relationship…
Rsync Source https://stackoverflow.com/questions/4493525/what-does-f-mean-in-rsync-logs Options Often used flags during my sync jobs: Rsync flags Primer on the bit flags and how to get to output bit flags for all actions (it does not do this by…
Keyboard/Terminal Search in history: Restore lost echo: List logged in users Storage List block devices Network Scans arp, nmap, tcpdump Routing Manipulate routing table to route only a segment through a ppp0 tunnel and default to a route through…
Doomsday rule It takes advantage of each year having a certain day of the week, called the doomsday, upon which certain easy-to-remember dates fall; for example, 4/4, 6/6, 8/8, 10/10, 12/12, and the last day of February all occur on the same day of…
Integrals $a$, $b$, $c$, $\alpha$, $\beta$ are constants $f$, $g$, $u$ are functions of a variable $x$ Basic properties Properties $$ \int _a ^a f(x)dx = 0 $$ $$ \int _b ^a f(x)dx = - \int _a ^b f(x)dx $$ Chasles' theorem: $$ \int _a ^b f(x)dx + \int…
Trigonometry Relations $$\cos^2(a) + \sin^2(a) = 1$$ $$1 + \tan^2(a) = \frac{1}{\cos^2(a)}$$ Addition $$\cos(a+b) = \cos(a)\cos(b) - \sin(a)\sin(b)$$ $$\cos(a-b) = \cos(a)\cos(b) + \sin(a)\sin(b)$$ $$\sin(a+b) = \sin(a)\cos(b) + \cos(a)\sin(b…
CD Paranoia Bargraph Used to indicate things during read. The letters are hierarchical; for example if a transport error occurs in the same sector as jitter, the bargraph will print instead of . Character Meaning Two blocks overlapped properly, but…