It's been two weeks since I installed Ubuntu 14.04 and today I noticed my lock screen has changed to a very old design.    I am new to Linux.  P.S. at this time light-locker is not installed in my computer. I wonder if it's necessary or not.
I'm using Ubuntu 14.04 but since some weeks I'm stuck with the old 13.10 lockscreen design for some reason.  I already tried compizconfig-settings-manager but it doesn't offer me any option for changing the lockscreen design and even resetting Compiz and Unity with   dconf reset -f /org/compiz/   didn't help.  Are there any other ways to get the new lockscreen back?
Square roots -- positive and negative How to match all occurrences of a regex I did some mathematical induction problems on divisibility   $9^n$ $-$ $2^n$ is divisible by 7. $4^n$ $-$ $1$ is divisible by 3. $9^n$ $-$ $4^n$ is divisible by 5.   Can these be generalized as $a^n$ $-$ $b^n$$ = (a-b)N$, where N is an integer? But why is $a^n$ $-$ $b^n$$ = (a-b)N$ ?  I also see that $6^n$ $- 5n + 4$ is divisible by $5$ which is $6-5+4$ and $7^n$$+3n + 8$ is divisible by $9$ which is $7+3+8=18=9\cdot2$.  Are they just a coincidence or is there a theory behind?  Is it about modular arithmetic? How to update a pull request from forked repo? What does it mean to "align" partitions? I am familiar with what partitions are, but I saw , and realised I didn't know what "aligned partitions" are.  So what does it mean to "align" partitions? What are the benefits, and the downsides? Are normal subgroups transitive? Can you explain more?  I do not know when we can use them in the sentence.  Can we use them instead of each other?     They have a beautiful home.   They have a beautiful house. From my old HD (Ubuntu 16.04) I copied ~/.thunderbird and other programs to the new disk with Ubuntu 18.04 installed. All went good. I tried to install Opera. The installation was unsuccessful, a window asking something was held. After that Thunderbird Local Folders -> Inbox (only) was invaded by large icons like this screenshot  Flowers, plants, trucks and others. I restarted but those images are still there. Opera was successfully installed. What can I do to remove them? Why is glass transparent? How to copy a dictionary and only edit the copy Let $m\in \mathbb{N}$ and $c_1,c_2,\ldots,c_m \in \mathbb{R}_+$. Show that $$\lim_{n\rightarrow \infty} \sqrt[n]{c_1^n+c_2^n+\ldots+c_m^n} = \max\{c_1,c_2,\ldots,c_m\}$$  My attempt: Since $$\lim_{n\rightarrow \infty} \sqrt[n]{c_1^n+c_2^n+\ldots+c_m^n} \leq \lim_{n\rightarrow \infty}\sqrt[n]{\max\{c_1,c_2,\ldots,c_m\}} = \lim_{n\rightarrow \infty} \sqrt[n]{n}\sqrt[n]{\max\{c_1,c_2,\ldots,c_m\}}=\lim_{n \rightarrow \infty} \max\{\sqrt[n]{c_1^n},\sqrt[n]{c_2^n},\ldots,\sqrt[n]{c_m^n}\}=\lim_{n \rightarrow \infty}\max\{c_1,c_2,\ldots,c_m\}=\max\{c_1,c_2,\ldots,c_m\}$$  it follows that $\lim_{n\rightarrow \infty} \sqrt[n]{c_1^n+c_2^n+\ldots+c_m^n}$ is bounded, but I don't think it's monotonically decreasing, at least I can't prove this. Can anybody tell me whether the approach I have chosen is a good one, whether what I have done is correct and how to finish the proof? How to minimize $|z_1 - z_2|^2 + |z_1 - z_4|^2 + |z_2 - z_3|^2 + |z_3 - z_4|^2$? If $z_1,z_2,z_3,z_4 \in \mathbb{C}$ satisfy $z_1 + z_2 + z_3 + z_4  =  0$ and $|z_1|^2 + |z_2|^2 + |z_3|^2 + |z_4|^2 = 1$, then the least value of $|z_1 - z_2|^2 + |z_1 - z_4|^2 + |z_2 - z_3|^2 + |z_3 -  z_4|^2$ is $2$.   I solved this by taking two of the values to be $\frac{1}{2}$ and other two as $-\frac{1}{2}$. But I couldn't prove this in an efficient manner. How to detect using c# if a pendrive is plugged into a USB port? Is there a way to find out when in a LAN anyone plugs in a pendrive to the USB port?  Programatically (in C# preferably) or through some tool. Basically I'd imagine a client application sits on each terminal and monitors the USB ports and sends the information to the server.   a.) Can I get the details of the file(s) being copied? b.) Is there a way to do this without a client application?   EDIT  I dont want to disable the USB port entirely. its to be on a need to have basis. Basically just want the users on the LAN to share data responsibly and know that whatever data is tranfered is monitored and logged and can be questioned later. I need to do a lot of cleaning in my Virtual Machine whose Operating System is Ubuntu.  Normally in Windows, there is this kind of directory that contain temporary files and that should be cleaned :  C:\Documents and Settings\Administrator\Local Settings\Temp   Does it exist such a directory in Ubuntu? If yes, what is it?  Thank you a lot. 8.4 - Use entity browser in a module block from in same way as I would in a custom block Renaming attributes/fields in shapefile attribute table using QGIS I would like to rename some fields in my attribute table:  Like rename &quot;XRF_N3&quot;in something else. It seems quite a easy issue but I don't find any information about how can I do that. Story about lost colonized planet sent into orbit around "free" star I found the following blog title without a question mark from :     How to ease Afghanistan’s progress in cricket   Is it grammatical, if we don't put question mark in questions of titles? I think this blog title should have been like this:     How to ease Afghanistan’s progress in cricket?   I also found the following blog title from  without a question mark:     Election rigging 101: How to steal a mandate   However, I found a question mark from other blog title of :     Elections 101: What is the ECP and what does it do on election day? Where to or how to ask "Best of" Questions for what software tools to use I am wondering where is a good place or how is a good way to ask a question on what software tools to use for a specific task.  A lot of the time when searching for information on these types of problems stackoverflow comes up with the top and actually useful discussions and answers, but the question is locked.  I completely understand the point of discouraging "best of" or list questions as discussed in this question () and agree they often aren't constructive enough to justify the effort in moderating them.  What I am wondering is where is the right place to have a discussion like this? Stackoverflow has a good and active community so perhaps there is another section or related site I can ask less specific questions. And I do find some value in reading people's opinions, even if subjective on issues like this.  Here are some examples of the kind of questions I mean:    and   First results in google when searching for those subjects and some useful discussion.  Perhaps asking a question like this but with a strict and detailed specification it might be considered a valid and reasonable question to ask on stackoverflow; perhaps it's just a case of re-thinking how to ask a question. Or perhaps there's a more relevant place for this kind of discussion. Please let me know what you think. Proving convergence of sums: If $\sum_{n=1}^{\infty}a^2_n$ and $\sum_{n=1}^{\infty}b^2_n$ converge then $\sum_{n=1}^{\infty}a_nb_n$ converges