/usr/bin/su question regarding setuid By default, /usr/bin/su has -rwsr-xr-x privilege. When I revoke the setuid from su file, non-root users are not able to execute su command to login as a different user. Why is this? Shouldn't it work because su file already has that execute privilege on its other(public) class?
Linux - why do the su and sudo binaries need to be set-UID root? I am trying to find the correct reason for the stated question. My understanding is that:   sudo needs to read the /etc/sudoers file which is only readable by root, which is why it needs to be set-UID root su is going to create a new shell with a different real and effective UID, and needs to check the password. To check the password, it needs to read /etc/shadow, which is why it needs to be set-UID root. After checking password, it would need to call setuid() on the forked process, and to use an arbitrary UID argument, its parent process must have root as effective UID, so this also makes another reason.   Are the above reasons correct ?
Lowest volume is still too loud—how can I make it even lower? The lowest volume I can get by pressing the volume keys is still too loud when I'm wearing headphones. How can I make it even lower?   I have a Mac Mini 2011 (5,1) running Mountain Lion. Say I had a Core i7 Laptop with 16GB of RAM and a 750gb drive.  Is there a mechanism where I can partition the HD into a Linux, Windows, OS X, Shared Data, Hypervisor setup where I boot a small hypervisor. I can start/stop a linux, Windows and OS X virtual machine and interact with them all from the hypervisor?   Code, Test, etc?  is this a type 1 Hypervisor?  I suppose I could run a small linux install and VmWare but could VmWare read the virtual machines from a physical hard disk partition versus a file based setup (.vmdk files)? I have build a website for a finance company.  The Cognito Form is on the website as an application form.  I would like the information sent automatically to the finance company's email address (as soon as the form is submitted) without having to log into Cognito Forms. The finance company needs to know the exact moment the application for finance comes in. The finance company can not possibly log in to Cognito Forms 24/7 to check if there are any finance applications. I just try to visualize some points using GeoServer to publish them as WMS and bind this WMS to my Openlayers website using the GeoServer internal Heatmap process to visualize it. I don't want to use the Openlayers Heatmap function.   But there seem to be some problems, look here:    I'm using this Openlayers implementation to bind my WMS URL:    Changing the params to:  params: {'LAYERS': 'test:points','TILED': true,'STYLES': 'heatmap'},   And using this as SLD to define the Heatmap:    Any ideas why this happens? I posted this at  and got redirected here. This does indeed look like a better place to ask.  I would like to decorate my headlines (section, subsection, etc.) by adding a background color. I would like this box filled with a single solid color to span across the entire typearea.  This picture is a screenshot of an OpenOffice document where the headline has the formating, layout and color I want.    Requirements on a solution   The resulting style is supposed to be used by others, meaning an equivalent latex output to the picture above shall be created by this code:  Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text   \subsubsection{This is a headline}  Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text Some Text  If the section is supposed to be unnumbered one should be using \subsubsection*. LaTeX still needs to be in charge of the whitespace between paragraphs and the blue box.   What I have tried so far  As far as I can google the headline together with the section numbering are a simple paragraph. Latex adds some skips before and after and squeezes in a few commands that modify the font(s).  My ideas revolve around locking this paragraph in a \colorbox. The colorbox macro works like this: \colorbox{color}{the content around which to draw a box filled with the specified color}. My problem is I can't get a grasp on this paragraph.  The easy 80%  My work is based on koma-script and by redefining \othersectionlevelsformat and \(sub)*section. I can draw two boxes, one surrounding the section numbering and another surrounding the section title. However this has 3 open issues:   the upper edges of the boxes are unaligned and the box with the title is slightly larger than the line with the numbering The box around the title does not strech to the right end of the typearea the box around the numbering doesn't grow if the title spans multiple lines (no surprise here)   The hard 20%  I tried to make latex put the section numbering into a \savebox I could access later and put as part of the title. That would eliminate the need for two boxes and solve all three of my problems at once, but that doesn't work. I only get to modify the title before the actual numbering is done. So while I can put the numbering into a savebox, I can't do anything with it until it's too late.  I tried putting the \section ... statement into a colorbox, but it doesn't like that and the document fails to compile with ! LaTeX Error: Something's wrong--perhaps a missing \item. The same holds for saveboxes. I guess colorbox uses those.  I tried putting the \section ... statement in a minipage and put a box around that. This has two issues. 1st: latex doesn't put any empty space above a section. 2nd: not only the section numbering and title have the background but also the empty space between section title and first paragraph.  So how can one hack latex to do a section title formating as shown in the screenshot above? How to force restart an iPhone with broken home button Earlier today I was on my iPhone and it randomly froze so I turned it off. When I went to unlock it it wouldn't move. I couldn't unlock it or tap anything. So now I can only stay on the lock screen. I read on the Apple website that I should "force restart" it by pressing my home button and power button at the same time. The problem is my home button is stuck and doesn't work. What should I do? Note: If you're looking for a simple explanation as to why comments aren't required on downvotes, see .   I used to get "upset" (though that is too strong a term) when I got downvoted without comment. If my answer isn't good enough then I'd like to know why. Not only does it improve the answer for the OP but it improves my knowledge too.  Where the down-vote has been explained I've found it useful &amp; it has improved my answer, or forced me to delete the answer if it was totally wrong.  So is there any way we can encourage people to leave a comment? Perhaps they don't lose rep if they explain their down-vote?  I must admit though that I haven't always explained my down-vote either so you could call me a hypocrite. I've also grown a thicker skin over the months of using SO (it seems to have come with the higher rep score ;-)), so I'm less bothered about this now. Check for column name in a SqlDataReader object Articles: When do I use "a", "the", or "__"? How do I know whether to use the definite (the) or indefinite (a, an) article, and when to omit it altogether? Reason for the current trend to use «she» as the gender-neutral pronoun? Let thing of a bird standing still in a box on top of a weighing machine that shows a mass $m_0$. Now, imagine that the bird is flying, still in the same box and the same weighing machine shows a mass $m_1$. As the bird when flying, is applying a force towards the weighing machine, could we deduce that $m_0 = m_1$? I'm asking this question because saying that these masses are equal makes me as uncomfortable as saying that they are not equal and can't figure the right answer. So does $m_0 = m_1$ and why? Very difficult integral (for me) Could someone point me to an online resource where I can look up  $$ \int_{-\infty}^\infty \int_{-\infty}^\infty \int_{-\infty}^\infty \frac{\cos(\vec k\cdot\vec x)}{\sqrt{|\vec k|^2+m^2}}\,dk_1\,dk_2\,dk_3$$  where $\vec k$ and $\vec x$ are 3-vectors, and $m$ is a constant.  Also, if you know how to do it step by step and want to show off your fancy integration, that would also be very helpful.  Thanks ;) what is the total number of distinct arrangements of $n$ oranges and $n$ apples around a round table? I have no idea how to go about. How can I stop iPhone prompting me to setup Apple Pay in Settings? Solving the matrix equation $AP=PB$, where $A$ and $B$ are similar Currently I'm stuck with this problem:     The following matrices are similar to each other.      $$A=\begin{bmatrix}-3&amp;0\\8&amp;4\end{bmatrix},\qquad B=\begin{bmatrix}-4&amp;4\\-2&amp;5\end{bmatrix},\qquad C=\begin{bmatrix}k&amp;1\\m&amp;-2\end{bmatrix}.$$      How do you find the matrix $P$ such that $AP = PB$?       And how can you calculate the values of $k$ and $m$?      Thank you in advance. sudo: /etc/sudoers is owned by uid 501, should be 0 To run programs as sudo without password, I edited /etc/sudoers with wrong content.   Then I re-edited it with Mac's default text editor(course sudo cannot be used when /etc/sudoers is wrong).  I tried to run sudo agin, and get this error:   sudo: /etc/sudoers is owned by uid 501, should be 0 sudo: no valid sudoers sources found, quitting   What should I do? I cannot remember the root password (maybe I haven't ever set root password before). How do I delete a 'locked' file? On Windows XP, when I try and delete a specific file it says:     Cannot delete blah.blah: Make sure the   disk is not full or write-protected   and that the file is not currently in   use.   How can I go around this warning and delete it anyway? In my calculator why does $\sqrt4 -2=-8.1648465955514287168521180122928e-39?$ I have tried this on my Windows 7 calculator with $\sqrt9 -3 $ it too gives some weird answer- ie$1.1546388020691628168216106791278e-37$. And so for any $n$(positive) $\sqrt n^2-n= wierd_ .answer$ Why does this happen? I'm trying to run this command in the terminal:  sudo apt install software-properties-common   This is the error message I get:  E: Could not get lock /var/lib/dpkg/lock-frontend - open (11: Resource temporarily unavailable)   E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend),     is another process using it? Hi i want to put this simbol "%" in the tick labels only in the x axis how can i do?