I am not able to add or update any repositories on my PC. The following error encountered when I tried updating using sudo apt-get update E: The repository 'http://ppa.launchpad.net/screenlets/ppa/ubuntu bionic Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details.  This error mentions screenlets repository but I am getting the same error when I try to add any repository.I was getting the same error before adding screenlets repository.  The following are my specs fetched using neofetch: OS: Ubuntu 18.04.4 LTS x86_64 Kernel: 4.15.0-109-generic Packages: 1701 Shell: bash 4.4.20 CPU: Intel Core 2 Duo E7200 (2) @ 2.306GHz GPU: Intel 4 Series Chipset Memory: 1655MiB / 7848MiB It is actually lubuntu 18.04 the question here is that not only I want to add repositories but also update the existing ones. Also, installing applications from snap is also not working but that could be a different thing altogether.
When updating, I get the following error message:   W: The repository 'http://ppa.launchpad.net/mc3man/trusty-media/ubuntu xenial Release' does not have a Release file.   Here, I find another statement on this error:   This recommends removing certain PPAs; and, I'm not sure if I should do that since it might mean not getting the updates that I need.    Is this what I should do?
This was a question from my textbook. This is how I approached it.   For the first part, you can do c(10,5) so you choose 5 of the 10 to be on a team.   For the second part, you have 10 ways to choose the "best player" and you multiply it by c(10,4) to pick the other 4 players. However, I am not sure how you can exclude the "worst player". Although this sounds subjective, I believe the question is saying that the "best" and "worst" players are distinct, whereas the other players aren't. Can the term "etymology" be applied to a phrase or only individual words? I have always heard the term used in referring to a single word. When browsing questions on this site, I've seen it used applied to entire phrases, and have suppressed the compulsion to edit them and replace the term with origin. Where did the convention of using single dashes for letters and doubles dashes for words come from and why is continued to be used?  For example if I type in ls --help, you see:    -a, --all                  do not ignore entries starting with .   -A, --almost-all           do not list implied . and ..       --author               with -l, print the author of each file   -b, --escape               print octal escapes for nongraphic characters       --block-size=SIZE      use SIZE-byte blocks   -B, --ignore-backups       do not list implied entries ending with ~ ...   I tried googling - and -- convention even with quotes with little success. I'm looking for a movie I've seen as a kid, the details are foggy and sparse but I'll try my best following :  What is it?: An animated movie. Tell us what it isn't: It is not . Tell us what made it memorable: A planet where some brain-sucking insect-like aliens live, also an old bald man lives on the same planet. When did you see this film?: Late 80's, early 90's. How old was it?: If I've seen the movie on TV in Spain, is a pretty safe bet that it will be at least 5 years old. Was it part of a series?: I don't think so. Plot: No clue, sorry. What language was it in?: The movie was dubbed to Spanish (Spain).  No detail is too insignificant  What details can I recall?:  Sci-Fi story with one character being an old bald man living on a planet where some insect-ish aliens can open your skull and suck your brain. Habitat of those insect-ish foes was depicted in light blue colors, I kinda remember giant mushrooms as well. A young boy befriends the old baldie, the boy came to the planet with some adults.   Other details I'm not completely sure (maybe my mind is filling the gaps):  I think that the movie was drawn using , not 100% sure though. I cannot remember which year I've seen the movie, but it should be late 80's or early 90's. I'm pretty sure that I've seen the movie in Spanish TV (not rented videotape). Somehow the young boy was the young version of the old baldie (time travel?). The old man lives in a wood house near the brain-sucking insect habitat, as many old man does he spend his time on the porch.    Try to offer unique details As anyone would expect from this kind of movie, there's a scene where the alien insects attack a group of people trying to suck their brains. A young boy was with those adults and survived with injuries in his head. The old bald man have some surgery in his head due to an attack he suffered years before. Any way to tell apart a CPU defect from a mainboard defect? Find Total number of ways out of N Number taking K numbers every M interval I have been stuck in a problem, that has thrown my brain out of the coding. This problem is at very high priority and I need the solution as early as possible. Problem is as :  There are exactly N advertising boards on the highway. Now a company want to advertise on some of these advertising boards(each advertising board costs some money) .  Company strategy is that, they want at least 'K' advertisement should be there among M consecutive advertising boards. But at the same time Company want to pay minimum for its advertisement .  Now, what is the total number of ways, different ways Company can advertise meeting its minimum cost strategy.  As for Example: N= 3, M = 2, K=1 ==> there is only one way for minimum cost, ie. 0C0 , where '0' denotes No company advertisement, and 'C' denotes company advertisement board.  Similarly, for N =4, M =2, K =1 ==> there is 3 possible ways, ie. C0C0, 0C0C, 0CC0.  Hope to get a reply from someone soon. Thanks. Passing Javascript variable to Is an automorphism of the field of real numbers the identity map? Is an automorphism of the field of real numbers $\mathbb{R}$ the identity map? If yes, how can we prove it?  Remark An automorphism of $\mathbb{R}$ may not be continuous. How do I fork a process that doesn't die when shell exits? Is there a way to know when a systemd timer will run next? I am testing a systemd timer and trying to override its default timeout, but without success. I'm wondering whether there is a way to ask systemd to tell us when the service is going to be run next.  Normal file (/lib/systemd/system/snapbackend.timer):  # Documentation available at: # https://www.freedesktop.org/software/systemd/man/systemd.timer.html  [Unit] Description=Run the snapbackend service once every 5 minutes.  [Timer] # You must have an OnBootSec (or OnStartupSec) otherwise it does not auto-start OnBootSec=5min OnUnitActiveSec=5min # The default accuracy is 1 minute. I'm not too sure that either way # will affect us. I am thinking that since our computers will be # permanently running, it probably won't be that inaccurate anyway. # See also: # http://stackoverflow.com/questions/39176514/is-it-correct-that-systemd-timer-accuracysec-parameter-make-the-ticks-slip #AccuracySec=1  [Install] WantedBy=timers.target  # vim: syntax=dosini   The override file (/etc/systemd/system/snapbackend.timer.d/override.conf):  # This file was auto-generated by snapmanager.cgi # Feel free to do additional modifications here as # snapmanager.cgi will be aware of them as expected. [Timer] OnUnitActiveSec=30min   I ran the following commands and the timer still ticks once every 5 minutes. Could there be a bug in systemd?  sudo systemctl stop snapbackend.timer sudo systemctl daemon-reload sudo systemctl start snapbackend.timer   So I was also wondering, how can I know when the timer will tick next? Because that would immediately tell me whether it's in 5 min. or 30 min. but from the systemctl status snapbackend.timer says nothing about that. Just wondering whether there is a command that would tell me the delay currently used.  For those interested, there is the service file too (/lib/systemd/system/snapbackend.service), although I would imagine that this should have no effect on the timer ticks...  # Documentation available at: # https://www.freedesktop.org/software/systemd/man/systemd.service.html  [Unit] Description=Snap! Websites snapbackend CRON daemon After=snapbase.service snapcommunicator.service snapfirewall.service snaplock.service snapdbproxy.service  [Service] # See also the snapbackend.timer file Type=simple WorkingDirectory=~ ProtectHome=true NoNewPrivileges=true ExecStart=/usr/bin/snapbackend ExecStop=/usr/bin/snapstop --timeout 300 $MAINPID User=snapwebsites Group=snapwebsites # No auto-restart, we use the timer to start once in a while # We also want to make systemd think that exit(1) is fine SuccessExitStatus=1 Nice=5 LimitNPROC=1000 # For developers and administrators to get console output #StandardOutput=tty #StandardError=tty #TTYPath=/dev/console # Enter a size to get a core dump in case of a crash #LimitCORE=10G  [Install] WantedBy=multi-user.target  # vim: syntax=dosini Normalizing constant in Bayes theorem I read that in Bayes rule, the denominator $\Pr(\textrm{data})$ of   $$\Pr(\text{parameters} \mid \text{data}) = \frac{\Pr(\textrm{data} \mid \textrm{parameters}) \Pr(\text{parameters})}{\Pr(\text{data})}$$   is called a normalizing constant. What exactly is it? What is its purpose? Why does it look like $\Pr(data)$? Why doesn't it depend on the parameters? Format numbers in django templates Why does Linux show both more and less memory than I physically have installed? Unmet dependencies unable to fix I'm running ubuntu 14.04. I cannot use software center to install anything, even a local deb package so I have to rely on Terminal.  Recently I was trying to install mysql-server which generated error which I could pin-point was the required version of libstdc++6 . My system had 4.8.x while mysql 5.6 required >=4.9. Trying the usual upgrading process and unsuccessful, I consulted my sys admin, who tried installing the 4.9 package manually(using a local .deb package), which failed as well citing unmet dependencies.   At present, what I have is a system with error saying no new software can be installed.  The sudo apt-get install -f gives following output:  Reading package lists... Done Building dependency tree        Reading state information... Done Correcting dependencies... failed. The following packages have unmet dependencies:  libstdc++6 : Depends: gcc-4.9-base (= 4.9.2-10) but 4.9.1-0ubuntu1 is installed  libstdc++6:i386 : Depends: gcc-4.9-base:i386 (= 4.9.2-10) but 4.9.1-0ubuntu1 is installed E: Error, pkgProblemResolver::Resolve generated breaks, this may be caused by held packages.   I checked for held packages using  dpkg -l | grep ^h dpkg -l | grep hold   Result: nothing.  Also tried to find the broken package, if any but the file  /var/log/dist-upgrade/apt.log doesn't exist.  So, what should/can I do now. Adding Items to the List Using JQuery Mobile in Javascript I'm building a small chat. Now I see but in other chats (whatsapp, facebook mobile chat, sms ...) that the arrangement is always the same:  Left: the chat partner. right: myself      Why is that? I want to implement an addition key layer, so that I can access non-alphanumeric keys without having to move my wrists.  I've been using Autokey for this purpose, but the experience was unsatisfactory: it had occasional lags and let original keystrokes slip into certain apps.  So I need a low-level solution. Using RegEX To Prefix And Append In Notepad++ I have quite a large list of words in a txt file and I'm trying to do a regex find and replace in Notepad++. I need to add a string before each line and after each line.. So that:   wordone wordtwo wordthree   become   able:"wordone" able:"wordtwo" able:"wordthree"   How can I do this? What is the relationship between redshift and conformal time ?   For example in a paper i found:   taking $z_e = 3234 $ at the time of radiaton-matter equality yields the conformal time $\frac{\eta_e}{\eta_0} = 0.007$ and taking $z_E=0.39$ at matter-$\Lambda$ equality yields $\frac{\eta_E}{\eta_0}=0.894$ and setting redshift at decoupling $z_d=1089$ yields $\frac{\eta_d}{\eta_0} = 0.0195$  where $\eta_0$ is the present decoupling time.  Further some cosmological parameters are given as :  $\Omega_r = 8.36 \times 10^{-5}, \Omega_m = \Omega_b + \Omega_{dm} = 0.044 +0.226, \Omega_\Lambda = 0.73,  H_0=0.72$  Now how can i calculate all those $\eta_e, \eta_E, \eta_d, \eta_0$ from given redshift values and/or above parameters ? I searched whole of my text books trying to find an explicit relation for conformal time $\eta$ but all i got was $ \mathrm{d}t=a(t)\mathrm{d}\eta$. Any help would be very helpful. An equivalent condition with $\{0\}$ being the only nilpotent ideal