so as title says, I cannot boot anymore after I removed python. I had anaconda before and certain packages didnt work anymore so I wanted to remove python and anaconda both to reinstall python fresh. However, I wasnt very successful. After removing python the terminal from the left window disappeared aswell and I couldn't open terminals anymore and if I wanted to log in, it didnt work. After rebooting, I didn't get into the GUI, but only had that tty terminal. These are pictures from boot. Can I still save my ubuntu version? Or if not, can I still save the data on it? I meanwhile managed to access my files via paragon linux software from windows. At the moment I try to copy my original ubuntu files completely, but even only &quot;finding&quot; the files takes hours. So could I try to copy certain files into my ubuntu drive and then install them from tty terminal for example?
I am a new Ubuntu user running Ubuntu 13.04.  I've been trying to install and use a DeDRM tool, but I've been having problems doing so. I was following some directions that said I needed a version of Python 2.7, but not anything Python 3.0 or later (because 3.0 versions are missing some necessary libraries?). I tried to install Python 2.7.5.6, but it didn't work. I thought it was probably because I had the later version of Python, so I went through terminal and removed Python 3.3, so I could install the earlier version of Python.  Now that I've uninstalled Python 3.3, a lot of applications no longer work, including the terminal and the Ubuntu Software Center. I have no idea how to fix this problem now.
I have lost functionality in the tool shelf. When I click on a selector or something in the bottom part of the tool self that you can hide and unhide, nothing happens. I can see the options but when I click it doesn't work. See screenshot where it says "Add Cylinder". Gravity as a gauge theory Currently, (classical) gravity (General Relativity) is NOT a gauge theory (at least in the sense of a Yang-Mills theory).   Why should "classical" gravity be some (non-trivial or "special" or extended) gauge theory? Should quantum gravity be a gauge theory?  Remark: There are some contradictory claims in the literature to this issue. To what extent gravity is "a gauge" theory?Obviously, GR is not a YM theory. So, why do some people say that gravity "IS" a gauge theory? I found this question relevant, e.g., then we handle GR in the Einstein-Cartan theory or any other theory beyond GR, like teleparallel theories or higher-derivative gravitational theories. So I think it could be useful to discuss the "gauge flavor" of gravity here. I need to remove all files with .gif extension except one file with name say "filename.gif". What is the optimal way to go about doing this in terminal?  The command rm *.gif removes all gif files including the file filename.gif. relation between $R^2$ of simple regression and multiple regression A very basic question concerning the $R^2$ of OLS regressions   run OLS regression y ~ x1, we have an $R^2$, say 0.3 run OLS regression y ~ x2, we have another $R^2$, say 0.4 now we run a regression y ~ x1 + x2, what value can this regression's R squared be?   I think it's clear the $R^2$ for the multiple regression should be no less than 0.4, but is it possible for it to be more than 0.7? Word for a person with a negative attitude Possible to click on an object in the viewport and the object list hierarchy automatically goes to that object also? Inspired by , say you have a 4x4 two dimensional array, write a function that rotates it 90 degrees. Raymond links to a solution in pseudo code, but I'd like to see some real world stuff.  [1][2][3][4] [5][6][7][8] [9][0][1][2] [3][4][5][6]   Becomes:  [3][9][5][1] [4][0][6][2] [5][1][7][3] [6][2][8][4]   Update: Nick's answer is the most straightforward, but is there a way to do it better than n^2? What if the matrix was 10000x10000? I am trying to use the Directory.GetFiles() method to retrieve a list of files of multiple types, such as mp3's and jpg's.  I have tried both of the following with no luck:  Directory.GetFiles("C:\\path", "*.mp3|*.jpg", SearchOption.AllDirectories); Directory.GetFiles("C:\\path", "*.mp3;*.jpg", SearchOption.AllDirectories);   Is there a way to do this in one call? At  there is this "only in ubuntu" that says "Built in virus protection":  What is the Ubuntu built it protection? What is the program in charge of this and how does it work? datatool with longtable How to unselect Excel Cell using Keyboard Shortcut? One can select multiple Excel cells (either contiguously or not) using the keyboard shortcut Ctrl+Click.   How do you deselect one or more of these previously-selected cells? How to read one filesystem from a whole disk image file? I ran these commands:  VBoxManage clonehd d6b9f0a5-98df-48ca-83c8-91a0809ec349 --format RAW Debian.raw sudo dd if=~/.VirtualBox/HardDisks/Debian.raw of=/dev/sda5   When I try to mount the partition, I get this complaint:  EXT4-fs (sda5): VFS: Can't find ext4 filesystem   Now I know that the VM had an ext4 partition. What did I do wrong? How are the AES S-Boxes calculated? I think the term "back and forth" gets thrown around a lot without much thought.  From Dictionary.com:         [fawrth, fohrth]      adverb    1.  onward or outward in place or space; forward: to come forth; go forth.   Wouldn't the term be more meaningful if "forth" was used first since you have to have a starting place before you can go "back"?  Examples:        I've been going back and forth from Houston to New York.   I've been going forth and back from Houston to New York.      Which is more correct? Changing pemalink structure to /%post_id%/%postname%/ I'm currently using permalink structure: /%year%/%monthnum%/%day%/%postname%/  I want to change that to: /%post_id%/%postname%/  I expect it to be:   faster (database is sorted by post_id?) shorter URLs (and clearly visible short verstions, just leaving the %postname%/ out) more SEO friendly - since my content is "evergreen" so publishing date is irrelevant (and written at each post, along with last update date) - so this would give shorter URLs, with no downsides compared to using year/month/day structure.   THE QUESTION: Does WordPress handle all the 301 redirects automatically? I can fix internal links to the new structure (though I'd expect that to be automatic as well), but worry about outsite links, pointing to my posts/articles.  If not, what's the best way to implement this change? Any links or full answers here are welcome.  I have about 120+ posts already, will this change affect the speed since it's not been done from the start? Is it true that the order of $ab$ is always equal to the order of $ba$? How do I prove that if $a$, $b$ are elements of group, then $o(ab) = o(ba)$?   For some reason I end up doing the proof for abelian(ness?), i.e., I assume that the order of $ab$ is $2$ and do the steps that lead me to conclude that $ab=ba$, so the orders must be the same. Is that the right way to do it? I set up a micro instance (Ubuntu, 32 bit) and assigned an elastic IP (23.23.245.104)  Public DNS: ec2-23-23-245-104.compute-1.amazonaws.com  I successfully ssh'ed to the machine and installed nginx.  Then I edited the server_name attribute in nginx's config file (/etc/nginx/sites-available/default)  server_name ec2-23-23-245-104.compute-1.amazonaws.com;   Restarted nginx and hit  but got a "could not connect" error.  What did I forget to do?  Thanks Exact Sequences of Modules and Rank Suppose that:  $0 \rightarrow M_{1} \rightarrow M \rightarrow M_{2} \rightarrow 0$  Is an exact sequence of $R$-modules (for $R$ commutative integral domain). Show that $\mathrm{rk}(M) = \mathrm{rk}(M_{1})+\mathrm{rk}(M_{2})$    I have shown the inequality $\mathrm{rk}(M) \geq \mathrm{rk}(M_{1})+\mathrm{rk}(M_{2})$, however for the opposite direction I'm lost. I tried to take $N$ as a linear independent subset and tried to decompose it into $N_{1}$ (the elements in $\mathrm{Ker}(g)$) and $N_{2}$ (the elements not in $\mathrm{Ker}(g)$), but I haven't got far, since $N_{1}$ gives us a linearly independent set in $M_{1}$, however $N_{2}$ can give us a linearly dependent set in $M_{2}$.   We define $\mathrm{rk}(M)$ in this case as the supremum over all cardinalities of the linearly independent subsets of $M$ (where the only finite linear combination equaling $0$ implies trivial coefficients for $r \in R$).  Would this be the proper way to show the result? I think I'm missing something important. Parallel universes: are there an infinite amount of universes? Parallel universe: in every universe, you are presented with a different decision. Does that mean there are an infinite amount of parallel universes? I.e., if in one universe I choose to go left, I am then presented with different choices vs if i choose right, and that creates more universes with more decisions to be made.  Or does it mean that in the end of one's life we end up in the same place, meaning that its just one parallel universe that eventually collides with the other. I am running Ubuntu 18.04. I wanted to install node and npm on my machine. The apt repository version of node is 8.x, whereas I wanted to have version 12.x (Current LTS version).  I followed the guide here:   As per the guide, I downloaded curl -sL https://deb.nodesource.com/setup_12.x -o nodesource_setup.sh  and then ran it with sudo -E ./nodesource_setup.sh    However, my machine fails to run sudo apt update with the following (full) output:  maxim@fujitsu:~/scripts$ sudo apt update Hit:1 http://gb.archive.ubuntu.com/ubuntu bionic InRelease                  Hit:2 http://gb.archive.ubuntu.com/ubuntu bionic-updates InRelease          Get:3 http://security.ubuntu.com/ubuntu bionic-security InRelease [88.7 kB] Hit:4 http://gb.archive.ubuntu.com/ubuntu bionic-backports InRelease               E: Repository 'http://security.ubuntu.com/ubuntu bionic-security InRelease' changed its 'Suite' value from 'bionic-updates' to 'bionic-security' N: This must be accepted explicitly before updates for this repository can be applied. See apt-secure(8) manpage for details. Do you want to accept these changes and continue updating from this repository? [y/N] N Fetched 88.7 kB in 8s (10.5 kB/s)                                                       Reading package lists... Done E: Failed to fetch http://security.ubuntu.com/ubuntu/dists/bionic-security/InRelease   E: Some index files failed to download. They have been ignored, or old ones used instead.    suggests that one should use apt update instead of apt-get update. None the less, I am running apt update.   suggests to answer "Y" to the prompt.  , from the Docker community, makes it clear that doing so is a bad idea.  However, , suggests that sometimes repositories change the names of package sources.  So my question is, is it OK to answer Y here? I don't want to  just blindly accept whatever error the package manager throws at me.