Hilbert’s program

Jovan Stosic February 4, 2020

In mathematics, Hilbert’s program, formulated by German mathematician David Hilbert in the early part of the 20th century, was a proposed solution to the foundational crisis of mathematics, when early attempts to clarify the foundations of mathematics were found to suffer from paradoxes and inconsistencies. As a solution, Hilbert proposed to ground all existing theories to a finite, complete set of axioms, and provide a proof that these axioms were consistent. Hilbert proposed that the consistency of more complicated systems, such as real analysis, could be proven in terms of simpler systems. Ultimately, the consistency of all of mathematics could be reduced to basic arithmetic.

Gödel’s incompleteness theorems, published in 1931, showed that Hilbert’s program was unattainable for key areas of mathematics. In his first theorem, Gödel showed that any consistent system with a computable set of axioms which is capable of expressing arithmetic can never be complete: it is possible to construct a statement that can be shown to be true, but that cannot be derived from the formal rules of the system. In his second theorem, he showed that such a system could not prove its own consistency, so it certainly cannot be used to prove the consistency of anything stronger with certainty. This refuted Hilbert’s assumption that a finitistic system could be used to prove the consistency of itself, and therefore anything else.

https://en.wikipedia.org/wiki/Hilbert%27s_program

Hardening and Security Guidance — ownCloud 9.1 Server Administration Manual 9.1 documentation

Jovan Stosic February 1, 2020

Enable HTTP Strict Transport Security

While redirecting all traffic to HTTPS is good, it may not completely prevent man-in-the-middle attacks. Thus administrators are encouraged to set the HTTP Strict Transport Security header, which instructs browsers to not allow any connection to the ownCloud instance using HTTP, and it attempts to prevent site visitors from bypassing invalid certificate warnings.

This can be achieved by setting the following settings within the Apache VirtualHost file containing the <VirtualHost *:443> entry:

<IfModule mod_headers.c>
  Header always set Strict-Transport-Security "max-age=15552000; includeSubDomains"
</IfModule>

Source: Hardening and Security Guidance — ownCloud 9.1 Server Administration Manual 9.1 documentation

File is locked – how to unlock – FAQ – ownCloud Central

Jovan Stosic February 1, 2020

Manually disable locking state:

  • put ownCloud in maintenance mode: edit config/config.php and change this line:
    'maintenance' => true,
  • Empty table oc_file_locks: Use tools such as phpmyadmin or connect directly to your database and run:
    DELETE FROM oc_file_locks WHERE 1
  • disable maintenance mode (undo first step).

Source: File is locked – how to unlock – FAQ – ownCloud Central

Local :: ownCloud Documentation

Jovan Stosic January 31, 2020

In the Folder name field enter the folder name that you want to appear on your ownCloud Files page. In the Configuration field enter the full file path of the directory you want to mount. In the Available for field enter the users or groups who have permission to access the mount; by default all users have access.

In addition to these steps, you have to ensure that Local storage is enabled in your ownCloud installation’s config/config.php file. It should have the following configuration:

'files_external_allow_create_new_local' => 'true',

Source: Local :: ownCloud Documentation