Currencies – What is the consensus about using a non-networked VM as a cold wallet / airgapped computer?

I'm wondering if a hardware wallet like a Ledger Nano S should be connected to the Ledger Live Desktop app running on a computer that is connected to the Internet rather than a completely cold wallet configuration. What about installing / running the Ledger Live app in a VM with the network components disabled? I know there is a chance that VMs will be violated or compromised, but I think the likelihood of accessing the home or output keys is low or absent.

Does anyone have experience or research data on this topic?

Network – The host network of vboxnet0 is not displayed on the MAC host computer

I'm using VirtualBox (version 6.0.4) to run Ubuntu (16.04.5 LTS) on a MacBook Pro. I'm using Drupalvm to build a Drupal development environment, and I'd like to start by saying that everything works, and I can use the PHPStorm debugging tool on the host side to debug code that runs on the virtual machine. So these are questions that I'm curious about; They do not affect my ability to use these tools, which are very helpful.

Here goes. Question 1: Drupalvm sets up two interfaces: a NAT adapter with port forwarding ( on the host to 22 on the guest) and a host-only adapter. In a host-only network, the guest computer should not be able to see the outside world, but my guest computer should. I know that because I see this website when I'm running a small PHP script that just redirects a header to an external website. How can that be?

Question 2: Simon Cotter's article on the VirtualBox network shows that in a host-only network, both the guest and host computers are connected to a network, vboxnet0, and I can see this network in my VirtualBox settings , On the host side, however, I do not see vboxnet0 when I go to System-> Settings-> Network. When I run ifconfig, I see vboxnet0 even if I shut down the virtual machine. Is this just a case of Apple's GUI, where not all adapters are displayed?

Set Associative Cache Exercise – Computer Science Stack Exchange

I am new to the cache and trying to figure out how to solve this problem. Can someone please provide me some materials to help me solve these kinds of questions? I've tried googling Set Associative Cache, but I have not found many sources on the subject.

Can someone guide me how to solve this question?

2 Set the associative cache

Accept the following contents of a cache in which all blocks are valid. The two-way cache (m = 2) is byte-oriented with a block size of 16 bytes.

Determine the contents of the 8-bit data bus if the processor is reading and the value B70A appears on the 16-bit address bus. If the requested data is not in the cache memory, swipe any previous data in this memory that will be overwritten when new values ​​are saved.

In this case, write the letter on the data bus and set new values ​​for LRU and KEY.
(Note: Numbering of the data columns: 0 … left column, 1 … right column.)

Needed information:

  • Data Content:
  • New value of the LRU:
  • New value of the LRU in raw no:
  • New value of Key:
  • New value of key in column no.:

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Differential Equations – How is a "constraint" imposed within a computer domain?

I need to set a "constraint" within the computer domain during the ODE solution with FDM. The problem is a boundary value problem implemented on the basis of pdetoae developed by @xzczd.

  1. Prepare the net

    L = 6; domain = {-L, L};
    Points = 21;
    Difford = 4; grid = array[# &, points, domain];
    (* The function can be found in the link above *)
    ptoafunc = pdetoae[u[x], Grid, Difforder];
  2. Discretize the system. Please note that the last condition you[0] == 0 from bc is what I want to enforce within the domain [-L,L]:

    eq = u[x] you[x] + u & # 39; & # 39;[x] + u & # 39; & # 39; & # 39; & # 39;[x] - 2 * u & # 39;[x] == 0;
    bc = {u[-L] == 0, u[L] == 0, u & # 39;[-L] == 0, u & # 39;[L] == 0, u & # 39;[0] == 0};
    del = #[[3 ;; -3]]&;
    ae = ptoafunc @ eq // del;
    aebc = ptoafunc @ bc;
  3. Release the resulting system FindRoot

    ic[x_] = 10 * Cos[[Pi]/ (2 l) x];
    solrule = FindRoot[{ae, aebc}, Table[{u@x, ic@x}, {x, grid}]]

Mathematica outputs the following error:

FindRoot :: nveq: "The number of equations does not match the number of variables in FindRoot[…], "

I also tried to remove one or two constraints among the first four bc, for example, u[-L] == 0, (* u[L] == 0, *) u & # 39;[-L] == 0, (* u & # 39;[L] == 0, *), The above error persists. Here without the last condition you[0] == 0The code works fine, but I have to set this "boundary condition" in addition to get a special function $ u (x) $, Thank you for every suggestion!

ports – nmap returns different results in two shells on the same computer

I'm using kali and metasploitable2 in Virtualbox and have connected them through the host-only networking mode. I can send ping and ssh from kali to metasploitable and have assigned the following IP addresses: (kali) and (metasploitable). For some reason, when I ran a simple scan, I could not see most of the open ports:

kali $ nmap -sV
Starting Nmap 7.70 ( on ​​16.06.2019, 09:04 CEST
Nmap scan report for
The host is active (0.011 seconds latency).
Not shown: 997 filtered ports
Open 80 / tcp http?
443 / tcp https open?
Open 8080 / tcp http-proxy?

But if I open another shell and execute the same command, I get a very different result:

kali $ nmap -sV
Starting Nmap 7.70 ( on ​​16.06.2019, 09:05 CEST
Nmap Scan report for
The host is active (0.00029s latency).
Not shown: 977 closed ports
21 / tcp open ftp vsftpd 2.3.4
22 / tcp open ssh OpenSSH 4.7p1 Debian 8ubuntu1 (protocol 2.0)
23 / tcp open telnet linux telnetd
25 / tcp open smtp Postfix smtpd
53 / tcp Open Domain ISC BIND 9.4.2
80 / tcp open http Apache httpd 2.2.8 ((Ubuntu) DAV / 2)
111 / tcp open rpcbind 2 (RPC # 100000)
139 / tcp open netbios-ssn Samba smbd 3.X - 4.X (Workgroup: WORKGROUP)
445 / tcp open netbios-ssn Samba smbd 3.X - 4.X (Workgroup: WORKGROUP)
512 / tcp open exec netkit-rsh rexecd
--- snip ----

This may be a beginner's question, but what could cause these differences between the cups? The environment variables were identical in both cases.

Do computer processors perform computations at runtime, or does the language programming compiler handle them?

When we write code in C # and then compile it into iL code and then convert it to native code at runtime, calculations (mathematical operators, if and else statements, ..) come with it Computer processors or C # compilersBecause the C # compiler performs some computation during encoding.

Proxy – Can the host computer communicate with the Blue Stacks instance?

I use 3/4 Instagram accounts on different Bluestacks instances. I use NordVPN on each one to assign each other a different IP.

On the host computer, I use Jarvee (Instagram bot), which lets you add multiple accounts and set a proxy for each one.

On Bluestacks, I downloaded Proxy Server from the Play Store and tried to get the host computer to connect to it. (Host-> Jarvee-> OS Instance-> VPN-> Instagram)

But I can not get a response from BS IP (example, not even a ping response. I'm new to VMs and do not really know how to get them to see each other. Any help is so much appreciated!

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