I have just booted my clean Ubuntu 18.04 LTS VM and tried to install some application with sudo apt install.  But got error message:     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?   What process created the /var/lib/dpkg/lock-frontend file in Ubuntu? How to gently stop it and take manual control on APT?
I get this error when trying to use apt-get:  E: Could not get lock /var/lib/dpkg/lock - open (11 Resource temporarily unavailable) E: Unable to lock the administration directory (/var/lib/dpkg/) is another process using it?     How can I fix this?
Etymology of "cut someone some slack" Teenagers. All the literature tells you one thing and one thing only – that  whatever they are doing, give them a break, cut them some slack, it's normal.      From the novel, Apple Tree Yard   I'm curious about the origins of . I know slacks are American English for trousers or pants, and a slacker is a lazy person. But what is a slack and how does one "cut" it? How to select the nth row in a SQL database table? Why doesn't a block rotate due to friction? Book or web site resources for an absolute beginner to learn about stocks and investing? I'm completely new to the world of investing and stocks. Knowing that I shouldn't invest or buy stocks until I know it well enough, I was wondering which cheap or affordable resources would be the best to get started?  I've seen quite a lot of books and websites that teach investing, but it's hard to choose.  To narrow it down, what book and/or what website would you recommend that does a good job teaching investing in stocks to beginners? In Revenge of the Sith, after first being Force-choked by Anakin and then given births to Luke and Leia, Padme Amidala eventually lost her life on Polis Massa. We later, however, see her in the funeral procession on Naboo. The question is, how did she get there?    I mean, whoever delivered her there must have faced a lot of difficult questions, not just from her family but also from both the people and the authorities, since she was the former queen of the planet. Whoever it was, he could not have been just somebody, because it most certainly must not have been an easy task. It most likely was not any of the Jedi, since the world was probably half full of Palpatine's collaborators who would have immediately given them away.  So, who was it? And how was it carried out, in practice? I cancelled the Microsoft Windows 10 Reservation and uninstalled KB3035583, but Windows 10 is still trying to install.   After I uninstalled KB3035583 and restarted my laptop as instructed, I could not find KB3035583 to hide it.   Now Windows 10 is sitting in my Windows Update saying that it will install when I restart my computer. How can I install Celestia on Ubuntu 18.04.1? Good Number Theory books to start with? I'm in Grade 11. I'm interested in elementary number theory and would like properly study it. I'm not intending to enter any competitions. Why is the triangle inequality property important for metric spaces? There is a property in the axiomatization of metric space: $d(x,z)\le d(x,y)+d(y,z)$. I understand that property applies well when it come to the measure of distances among points. However, that property seems to be irrelevant in the definitions of continuity, open set and some other key concepts.  My topology book says that it is asserting "the transitivity of closeness", a vague term that loses me. So why is that property important? Why did the founders (if any) of topology consider it at the first place? And what if that property is missed? How do you get to the Secret Room in the Tavern? My friend and I noticed that there seems to be an inaccessible room in the Tavern with something behind it. We saw that there was a Treasure Chest seemingly floating somewhere off the map.     In addition, if you walk up to the second floor of the Tavern and position your camera through the wall just right, you can highlight something called the Defender's Forge.   Confirmation of the speculation was confirmed in the notes for the 7.07 patch, which had a note that said the following:     Moved bonus-item crates back into the main section of the Halloween Tavern, out from the Secret Room.   What is this Secret Room? How do I get there? Do I need to beat the campaign first or something else? How can I securely erase a hard drive? I'm planning on selling a USB external hard drive that currently contains an old Ubuntu installation with stored passwords and banking information.  How can I securely erase the drive before selling it? Doubt on Rechargable LED Emergency bulb I have recently seen a  and I  was wondering how it is working.  In the event of a power failure, the LED bulb will turn ON automatically. That is, when the switch is ON and mains power goes off the bulb will detect that and turn ON. If the switch is OFF bulb will not turn ON. When mains are ON and the switch is ON the bulb will start recharging again.  It is just like a normal bulb. See the   My question is, how the bulb will detect the event of mains failure? Can somebody give me a hint on this? Compute the period of a decimal number a priori I noticed that , given an operation like $\frac{n}{m},\;n,m \in N$ that result in a periodic decimal number, computes really fast the length of the period.  E.g. $\frac{3923}{6173}$ has a period of 3086: .  I was wondering how this computation is done: is there some method to do this (except the trivial one of executing the division and looking for a sequence repetition) ? "Now" vs "by now" Consider these examples:   By now the desk should be looking significantly tidier!  By now, the failure of regulators to contain dangerous forces should be well accepted.  By now I own some forty copies of the magazine.  By now the blue of twilight is glowing.  He used leverage, but by now applied concerted discipline to contain his risks.    I wonder if I can use &quot;now&quot; instead of &quot;by now&quot; to convey the same meaning. I would think &quot;by now&quot; refers to a moment until now, but why not use past tense or present perfect tense in the these examples? SElinux: allow httpd to connect to a specific port My system is running CentOS 6.4 with apache2.2.15. SElinux is enforcing and I'm trying to connect to a local instance of redis through my python/wsgi app. I get Error 13, Permission denied. I could fix this via the command:  setsebool -P httpd_can_network_connect  However, I don't exactly want httpd to be able to connect to all tcp ports. How can I specify which ports/networks httpd is allowed to connect to? If I could make a module to allow httpd to connect to port 6379 ( redis ) or any tcp on 127.0.0.1, that would be preferable. Not sure why my paranoia is so strong on this, but hey...  Anyone know? Help identifying an error type "tried to help me learning" I have a friend from Russia who is trying to learn English and recently used the sentence "He tried to help me learning..." (implied: the English language)  It is obviously wrong and I corrected it telling her that she was supposed to say: "He tried to help me learn.", but I have a hard time explaining to her why it is incorrect since I'm not an expert on grammar either.  Is it a case of confusing the present simple and present continuous or does it have something to do with gerunds and infinitives? Any help would be highly appreciated! Suspended user cannot award bounty I asked a question on Stack Overflow: . I want to award my bounty to  by user  However, my Stack Overflow account is suspended recently for 7 days, and the suspension still has 5 more days to end.And I know I can't vote, ask, answer or comment as pointed on  by  with the sentence below.  You will be unable to vote, ask, answer, or comment.  I couldn't find anything about not being able to accept an answer or award bounty so I tried to accept the mentioned answer above and award my bounty to it and I got a  Suspended users cannot vote  rejection which can be seen below with a screenshot.  I know this  If you do not award your bounty within 7 days, the highest voted answer created after the bounty started with at least 2 upvotes will be awarded half the bounty amount.  from . None of the answer given to my question is upvoted and the answer I mentioned is not the oldest one after the bounty started so it won't be awarded by community. What can I do? (except being a good guy and not get suspended :)) Showing a tensor is not a simple tensor Let $(e_1,e_2)$ be the standard basis of $\mathbb{R}^2$. Why can the element $e_1\otimes e_2 + e_2\otimes e_1$ in $ \mathbb{R}^2\otimes_{\mathbb{R}} \mathbb{R}^2 $ not be written as a simple tensor $v\otimes w$ for $v,w\in \mathbb{R}^2$?  If we suppose $e_1\otimes e_2 + e_2\otimes e_1=v\otimes w$, then can we conclude that $e_1=\lambda e_2$ for some $\lambda \in \mathbb{R}$? This would give a contradiction since $e_1$ and $e_2$ are linearly independent. However, I am not sure if the argument is valid. I moved postgresql's data directory by following the following steps:   Stop postgres cp -a source_data_directory destination_data_directory export PGDATA=destination_data_directory Changing data directory to destination_data_directory within postgresql.conf pg_ctl start   But when I run: "pg_ctl start" I get the following error. Can someone please help me figure out the error.   server starting postgres@Server:/usr/lib/postgresql/9.1/bin$ postgres cannot access the server configuration file "/home/destination_data_directory/postgresql.conf": No such file or directory GCD in a PID persists in extension domains