I want to block a user from installing or uninstalling any application in the system. Does anybody know how can I achieve this?
Can i prevent/restrict standard user from installing/uninstalling software in Ubuntu 12.04 desktop?
I have an external USB 3 disk drive (2TB capacity) that is most likely going to be moved from machine to machine. The disk has a GUID partition table and an ext4 partition. I am unable to write to the disk unless I elevate the process (sudo).  As of now I am thinking of trying one or both of the following and would like to know the cons of each -   chmod 777 /mnt/externalDrive chown nobody:nogroup /mnt/externalDrive   If I give 777 permission and user1 (UID:1005) writes to it and I later move the disk to another computer where user7 is UID:1005, what happens? Does user7 become the owner of the file on that computer? It seems to me that I will periodically have to run chown -R nobody:nogroup /mnt/externalDrive on the disk.  Is any of what I am considering an obvious bad practice? The disk will most likely contain videos, music and pictures none of it need to be protected like some financial data. What's the "Bad magic number" ImportError in python, and how do I fix it?  The only thing I can find online suggests this is caused by compiling a .py -> .pyc file and then trying to use it with the wrong version of python. In my case, however, the file seems to import fine some times but not others, and I'm not sure why.  The information python's providing in the traceback isn't particularly helpful (which is why I was asking here...), but here it is in case it helps:  Traceback (most recent call last):   File "run.py", line 7, in &lt;module&gt;     from Normalization import Normalizer Export iMessages in human readable form for archival I have a long (several months' worth) iMessage conversation with a contact.  He lost these messages when he re-installed his OS, but I still have the archive.  There is some important information there that we'd like to keep.  Is there a simple way to export this conversation for archival in a human readable form, and also keep any images?  I can select parts of the conversation, copy it to the clipboard and paste it into a rich text document, but this discards all images.  I'm looking for a way that keeps the images.  Note: I use iMessage on OS X only, not iOS.  (Ideally I'd also like to export all non-image file attachments, but I'm not expecting that this will be possible.) When exactly does combat start and surprise take effect? So say I'm going to ambush an orc. I successfully sneak up on him and I attack. The DM determines that the orc is surprised. The orc happens to get an initiative roll of 19, while I get a 10. How would this work? I can only think of two reasonable resolutions to this.   The orc, having a higher initiative, goes first. Since he's surprised, he does nothing. Then it's my turn. If the orc survives my attack, it is now his turn, and being that the orc has already gone through his round of surprise, he can now attack me or whatever, and combat proceeds as normal. I, having started the combat, go first. If the orc survives my attack, but he is surprised, so he does nothing. It is now my turn again, I attack again. If the orc survives my second attack, it is now his turn, and being that the orc has already gone through his round of surprise, he can now attack me or whatever, and combat proceeds as normal.   Which one of these is correct? neither? Does starting combat secure me a turn/action at the start of initiative order like in option 2? If option 1 is correct, could I ready an action to shoot the orc, effectively granting me a similar first attack as in option 2?  Sorry if this makes no sense. Does anyone know if there's a way to get an Android phone to reboot into recovery mode, from the Android command line?  Note:  I do NOT have adb access.  I do NOT know the magic power-on sequence to do it from the boot loader. I've tried the common things and nothing works.  I DO have root. (And can enter commands directly on the device using a terminal emulator.)  I know it's possible, somehow, because applications like ROM Manager do it. But how? I'm reading Linear Algebra by Hoffman, Kunze where the authors explained that a $n\times n$ matrix $A$ being invertible is equivalent to the fact that $A$ is row-equivalent to $n\times n$ matrix $R$ which is an identity matrix.  In the proof of the theorem, they wrote:     $$R= E_k\ldots E_2E_1 A$$ where $E_1,\ldots,E_k$ are elementary matrices. Each $E_j$ is invertible, and so $$A = E_1^{-1}\ldots E_k^{-1}~R\,. $$  ... Since, $R$ is a (square) row-reduced echelon matrix, $R$ is invertible if and only if $R=I\,.$  [...]   I couldn't get the conclusion, since any row of $R$ can't be zero, it has to be identity matrix $I\,.$ Why is it so?  Isn't there any other row-reduced echelon matrix other than the identity matrix having no zero row and invertible? Why is it so? Are Complex Substitutions Legal in Integration? This question has been irritating me for awhile so I thought I'd ask here.  Are complex substitutions in integration okay?  Can the following substitution used to evaluate the Fresnel integrals:  $$\int_{0}^{\infty} \sin x^2\, dx=\operatorname {Im}\left( \int_0^\infty\cos x^2\, dx + i\int_0^\infty\sin x^2\, dx\right)=\operatorname {Im}\left(\int_0^\infty \exp(ix^2)\, dx\right)$$  Letting $ix^2=-z^2 \implies x=\pm\sqrt{iz^2}=\pm \sqrt{i}z \implies z=\pm \sqrt{-i} x \implies dx = \pm\sqrt{i}\, dz$  Thus the integral becomes  $$\operatorname {Im}\left(\pm \sqrt{i}\int_0^{\pm\sqrt{-i}\infty} \exp(z^2)\, dz\right)$$  This step requires some justification, and I am hoping someone can help me justify this step as well: $$\pm \sqrt{i}\int_0^{\pm\sqrt{-i}\infty} \exp(z^2)\, dz=\pm\sqrt{i}\int^\infty_0\exp(z^2)\, dz=\pm\sqrt{i}\left(\frac{\sqrt{\pi}}{2}\right)$$  Thus  $$\operatorname {Im}\left(\int_0^\infty \exp(ix^2)\, dx\right)=\operatorname {Im}\left(\pm\frac{\sqrt{i\pi}}{2}\right)=\operatorname {Im}\left(\pm\frac{(1+i)\sqrt{\pi}}{2\sqrt{2}}\right)=\pm\frac{1}{2}\sqrt{\frac{\pi}{2}}$$  We find that the correct answer is the positive part (simply prove the integral is positive, perhaps by showing the integral can be written as an alternating sum of integrals).  Can someone help justify this substitution?  Is this legal? Countable union of countable sets(ZF) change caption in list of tables I would like to change the caption in the List of Tables in a way it is different from the caption in the corresponding table. How can I do that? Does there exist a command to do that? How can I stop Steam from loading when I start my computer? Every time I boot into OSX or Windows, Steam automatically starts.  Is there a way to stop Steam starting whenever I boot up my computer? I have installed a vlc in centos 6.5. I want to run it as root. But I get the following error,      "VLC is not supposed to be run as root. Sorry. If you need to use   real-time priorities and/or privileged TCP ports you can use   vlc-wrapper (make sure it is Set-UID root and cannot be run by   non-trusted users first)." Why isn't reflexivity redundant in the definition of equivalence relation? An equivalence relation is defined by three properties: reflexivity, symmetry and transitivity.  Doesn't symmetry and transitivity implies reflexivity? Consider the following argument.  For any $a$ and $b$, $a R b$ implies $b R a$ by symmetry. Using transitivity, we have $a R a$.  Source: Exercise 8.46, P195 of Mathematical Proofs, 2nd (not 3rd) ed. by Chartrand et al Proof using Prüfer encoding The question is as below:      Show that each vertex $v$ of a tree $T$ appears $deg(v)-1$ times in the Prüfer encoding of $T$, where $deg(v)$ is the degree of $v$ in $T$.   For this, I think there are 3 scenarios a leaf should be considered for: (1) when it is a leaf as part of a tree; (2) a leaf that has been discarded; (3) the remaining edge. I feel like this will result in a short proof which is only two (or so) statements long, but at the same time, feel it is too simple.   EDIT: I've had a look at this again and narrowed it down to 2 cases:   Case 1: The vertex $v$ in question has $deg(v)\ge2$. $v$ then loses its neighbours as the algorithm is applied repeatedly until $v$ becomes a leaf itseelf. At this point, $v$ is attached to another neighbour, leaving an edge. This means the algorithm can no longer be applied and we have obtained the final Prüfer Encoding for the tree $T$.  Case 2: The vertex $v$ has $deg(v)\ge 2$. It loses its neighbours as the algorithm is applied repeatedly but is deleted itself at some point in the process.   Have I gone about this wrong?  Thank you. Prove that $ S=\{0\}\cup\left(\bigcup_{n=0}^{\infty} \{\frac{1}{n}\}\right)$ is a compact set in $\mathbb{R}$. Prove that $ S=\{0\}\cup\left(\bigcup_{n=0}^{\infty} \{\frac{1}{n}\}\right)$ is a compact set in $\mathbb{R}$, but $\bigcup_{n=0}^{\infty} \{\frac{1}{n}\}$ is not a compact set.   (Can we use definition of compact set for this problem? ) How do you change the size of figures drawn with Matplotlib? How do you change the size of figure drawn with Matplotlib? Code: \documentclass[12pt]{article} \usepackage{pgfplots} \usepackage{float} \pgfplotsset{compat=1.17} \usepackage{tikz} \usetikzlibrary{shapes, arrows.meta, automata, positioning, matrix, calc} \usepackage[RPvoltages, american,siunitx]{circuitikz} \usepackage[margin=1in]{geometry}  \usepackage{steinmetz} \begin{document}         \begin{figure}[H]         \centering         \begin{circuitikz}             \draw(0,0) to[V = $\vec{V}_g$] ++(0, 3) to[R = 50 &lt;\ohm&gt;] ++(3, 0) to[C = 1&lt;\micro\farad&gt;, v = $\vec{V}_o$] ++(0, -3) to[short] ++(-3, 0);         \end{circuitikz}     \end{figure} \end{document}  Output:  As we can see, $\vec{V}_o$ is almost touching the capacitor. How to adjust the spacing for the voltage label? Actually, can  potentially solve the problem? Note that what I am trying to draw is based off of this: When is it appropriate to use the original pronunciation of a foreign word versus the English pronunciation? When reading to an audience, or speaking in conversation, when is it appropriate to use the original pronunciation of a foreign word versus the English pronunciation (assuming you know the appropriate pronunciation for it)? Is it considered rude, or condescending? Or is it considered a mark of being knowledgeable?  One of the things to consider are place names. When referring to Paris, France, should it be pronounced with the silent 'S' as the French would say it, or with the 'S'? Should Hiroshima be pronounced as a Japanese speaker would pronounce it slightly more emphasis on RO, rather than the SHI? Should Mount Pinatubo be pronounced as a Filipino speaker would pronounce it with shorter stronger vowels, or the longer vowels? (e.g. Pi as is 'pick' rather than 'pea'.) Should Wichita be pronounces as the original "shi" rather than the modern "chi"?  Pronounce pesos or sombrero as a Spanish speaker 'eh' or the English 'ay'?  (I can't think of other common words right now that aren't words taken from other languages like hurricane, boondocks, tornado, etc. which I think have (correctly) changed to English pronunciations.) How can I set the location (as it's picked up in CoreLocation services) in the iPhone Simulator? notation of distribution I have a question:      Does  $$N(0, x)$$ mean a normal distribution with mean $0$ and variance $x$? Or standard deviation $x$?   The notation seems ambiguous sometimes. "Open in terminal" not working on nautilus as root When using natilus as root, open in terminal used to work as using with any user. However, when I press open in terminal when using nautilus as root now, it does nothing.  How to solve it?  The error:  GLib-GObject-CRITICAL **: g_object_set_data: assertion 'G_IS_OBJECT (object)' failed