Every time I check for updates, I get:  W:Failed to fetch http://cz.archive.ubuntu.com/ubuntu/dists/saucy/main/binary-amd64/Packages  404  Not Found [IP: 217.31.202.63 80] , W:Failed to fetch http://cz.archive.ubuntu.com/ubuntu/dists/saucy/universe/binary-amd64/Packages  404  Not Found [IP: 217.31.202.63 80] , W:Failed to fetch http ://cz.archive.ubuntu.com/ubuntu/dists/saucy/main/binary-i386/Packages  404  Not Found [IP: 217.31.202.63 80] , W:Failed to fetch http ://cz.archive.ubuntu.com/ubuntu/dists/saucy/universe/binary-i386/Packages  404  Not Found [IP: 217.31.202.63 80] , E:Some index files failed to download. They have been ignored, or old ones used instead.   Some other suggestions are to look in /etc/apt/sources.list, but there is nothing about cz in that file, nor does it contain "ca.archive.ubuntu.com/ubuntu/..." mentioned is another answer on this forum.  This has been going on for a while and I hoped that some mirror list might be fixed and the problem might go away, but I finally feel it's worth mentioning.  Usually, I just get a warning, and updates still happen, but I had an issue trying to load a package today and I'm wondering if they may be connected.  I've been using ubuntu for several years, so I'm not a complete noob, but this is outside my knowledge area, and I haven't been able to google an answer.  Note: I added a space after two of the link : because my reputation is too low to post more that two links.  uname -a  Linux transition 3.13.0-65-generic #105-Ubuntu SMP Mon Sep 21 18:50:58 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux   This problem is not a duplicate of  because my problem is not with ppa, and none of the solutions there fixed my problem.
PPA seems to be constantly offline. Whenever I use sudo apt-get update, this error is shown:  W: Failed to fetch http://ppa.launchpad.net/ 404  Not Found   How do I fix these errors?
In An Introduction to Statistical Learning (James et al.), in section 3.7 exercise 5, it states that the formula for $\hat{\beta}_1$ assuming linear regression without an intercept is  $$\hat{\beta}_1 = \dfrac{\displaystyle\sum\limits_{i=1}^{n}x_iy_i}{\displaystyle \sum\limits_{i=1}^{n}x_i^2}\text{,}$$ where $\hat{\beta}_0 = \bar{y}-\hat{\beta}_1\bar{x}$ and $\hat{\beta}_1 = \dfrac{\displaystyle S_{xy}}{S_{xx}}$ are the usual estimates under OLS for simple linear regression ($S_{xy} = \displaystyle\sum\limits_{i=1}^{n}(x_i - \bar{x})(y_i - \bar{y})$).  This is not the actual exercise; I am merely wondering how to derive the equation. Without using matrix algebra, how do I derive it?   My attempt: with $\hat{\beta}_0 = 0$, we have $\hat{\beta}_1 = \dfrac{\bar{y}}{\bar{x}} = \dfrac{S_{xy}}{S_{xx}}$.  After some algebra, it can be shown that $\displaystyle S_{xy} = \sum\limits_{i=1}^{n}x_i^2 - n\bar{x}\bar{y}$ and $\displaystyle S_{xx} = \sum\limits_{i=1}^{n}x_i^2 - n\bar{x}^2$. From here, I'm stuck. I need help with STATS homework about normal distribution The distribution of sale price for new MacBook Air’s is approximately normally distributed with a mean of \$800 and a standard deviation of \$70. (a) Mr. Bob plans to spend between $700 \text{ and } $850 on a new Apple MacBook Air. What proportion of the available MacBook Airs can Mr. Bob afford? (b) What is the 90th percentile of computers of this type? (c) Show that a MacBook Air priced at \$1000 would be considered an outlier using the 1.5 × IQR rule. For a, I tried doing 850-700=50 and $\frac{50}{800} = \frac{1}{40}$, for b, I tried $m+(0.5 \times R)/y$ for c, I tried $1.5 \times 700 - 1.5 \times 850$ This is a question that has been addressed several times, not only here, but also in other sites of the stack exchange network (e.g. ). However, I cannot make any of the solutions work for me.  I'm running a command through ssh. Whenever I exit ssh, I want the command to die as well. This command is a daemon called ktserver that runs indefinitely until you press Ctrl-C.  I run it as follows: ssh -t compute-0-1 ktserver and, indeed, when I press Ctrl-C, the process ends gracefully and the ssh session ends.  However, if instead of pressing Ctrl-C, I kill the ssh process using the kill command (for example, sending SIGINT or SIGHUP), the ktserver process stays alive.  How can I make the ktserver always die independent on how ssh is killed?  EDIT: If, instead of ktserver I run something completely different, such as gedit, everything works like a charm (i.e. gedit dies when the connection dies). Therefore, there might be something wrong with the process itself. For example, I thought that it might be ignoring SIGHUP or SIGINT. However, when I run kill -1 ktserver or kill -2 ktserver, the process dies as expected.  EDIT2: As Mark Plotnick points out, the issue is related to the fact that there is no communication circulating on the ssh channel. I've confirmed by running ssh -t &lt;host&gt; read and killing the ssh process afterwards. readwas still alive and kicking. Height/Radius ratio for maximum volume cylinder of given surface area Or, an introductory guide to robust filename handling and other string passing in shell scripts.  I wrote a shell script which works well most of the time. But it chokes on some inputs (e.g. on some file names).  I encountered a problem such as the following:   I have a file name containing a space hello world, and it was treated as two separate files hello and world. I have an input line with two consecutive spaces and they shrank to one in the input. Leading and trailing whitespace disappears from input lines. Sometimes, when the input contains one of the characters \[*?, they are replaced by some text which is is actually the name of files. There is an apostrophe ' (or a double quote ") in the input and things got weird after that point. There is a backslash in the input (or: I am using Cygwin and some of my file names have Windows-style \ separators).   What is going on and how do I fix it? Is there any hint of of the first Wizarding War being an international event? Is there any hint that the MoM or anywhere else got support in combating voldemort the first time around? Or is everything completely UK-centric?  I can't remember anyone in the second war being specifically sent from europe to help, even though we see international wizards in book 4. But I don't think all the events of the first war are covered in the books.  So are other bodies like the MoM involved in the first war, or was it isolated in the UK? I have got a new installation of windows recently. Now when I do unpin items from taskbar that were there (IE, Edge, Explorer), they do come back after restart. A pinned chrome does not disappear though e.g.  Anything to fix this issue?  P.S. Just created a new user, and he has the same problem  P.P.S. Sign out is enough to get it back, no full restart needed A get() like method for checking for Python attributes If I had a dictionary dict and I wanted to check for dict['key'] I could either do so in a try block (bleh!) or use the get() method, with False as a default value.  I'd like to do the same thing for object.attribute. That is, I already have object to return False if it hasn't been set, but then that gives me errors like     AttributeError: 'bool' object has no attribute 'attribute' Does applying the Collatz conjecture algorithm to negative integers always result in sequences ending with $-1$ and then repeating themselves an infinite number of times? It is so for the first several seed values.  After hours of thinking and research, I don't know how to answer the question. At work we are being asked to create XML files to pass data to another offline application that will then create a second XML file to pass back in order to update some of our data. During the process we have been discussing with the team of the other application about the structure of the XML file.   The sample I came up with is essentially something like:  &lt;INVENTORY&gt;    &lt;ITEM serialNumber="something" location="something" barcode="something"&gt;       &lt;TYPE modelNumber="something" vendor="something"/&gt;     &lt;/ITEM&gt; &lt;/INVENTORY&gt;   The other team said that this was not industry standard and that attributes should only be used for meta data. They suggested:  &lt;INVENTORY&gt;    &lt;ITEM&gt;       &lt;SERIALNUMBER&gt;something&lt;/SERIALNUMBER&gt;       &lt;LOCATION&gt;something&lt;/LOCATION&gt;       &lt;BARCODE&gt;something&lt;/BARCODE&gt;       &lt;TYPE&gt;          &lt;MODELNUMBER&gt;something&lt;/MODELNUMBER&gt;          &lt;VENDOR&gt;something&lt;/VENDOR&gt;       &lt;/TYPE&gt;    &lt;/ITEM&gt; &lt;/INVENTORY&gt;   The reason I suggested the first is that the size of the file created is much smaller. There will be roughly 80000 items that will be in the file during transfer. Their suggestion in reality turns out to be three times larger than the one I suggested. I searched for the mysterious "Industry Standard" that was mentioned, but the closest I could find was that XML attributes should only be used for meta data, but said the debate was about what was actually meta data.  After the long winded explanation (sorry) how do you determine what is meta data, and when designing the structure of an XML document how should you decide when to use an attribute or an element? Changing capitalization of filenames in Git Ubuntu server shows me that I  use allmost all disk:  Usage of /:   95.5% of 118.12GB   And I try to find big folders and files, run ncdu:  ncdu 1.8 ~ Use the arrow keys to navigate, press ? for help                                                                                                                                                  --- / ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------     5.5GiB [##########] /root                                                                                                                                                                                    2.3GiB [####      ] /var   628.6MiB [#         ] /usr   209.9MiB [          ] /lib    28.2MiB [          ] /boot     8.6MiB [          ] /bin     7.7MiB [          ] /sbin     6.6MiB [          ] /etc   208.0KiB [          ] /run   112.0KiB [          ] /tmp    48.0KiB [          ] /opt e  16.0KiB [          ] /lost+found     8.0KiB [          ] /dev     8.0KiB [          ] /media     4.0KiB [          ] /lib64 e   4.0KiB [          ] /srv e   4.0KiB [          ] /selinux e   4.0KiB [          ] /mnt e   4.0KiB [          ] /home     0.0  B [          ] /proc     0.0  B [          ] /sys @   0.0  B [          ]  initrd.img @   0.0  B [          ]  vmlinuz   According to ncdu I use about 10 GiB of 128 GiB - it is about 10 %. Contradiction.  How to clean my ubutntu server without rebooting?  I thought that ncdu lies and used another apps to find big files and folders. All of them shows the same result as ncdu.  And df -h command shows that disk is full.  # df -h Filesystem      Size  Used Avail Use% Mounted on /dev/xvda       119G  113G     0 100% / udev            2.0G  8.0K  2.0G   1% /dev tmpfs           788M  212K  788M   1% /run none            5.0M     0  5.0M   0% /run/lock none            2.0G     0  2.0G   0% /run/shm   Update  sudo du -sch /* result:  /# sudo du -sch /* 8.7M    /bin 29M /boot 8.0K    /dev 6.6M    /etc 4.0K    /home 0   /initrd.img 210M    /lib 4.0K    /lib64 16K /lost+found 8.0K    /media 4.0K    /mnt 48K /opt du: cannot access `/proc/4470/task/4470/fd/4': No such file or directory du: cannot access `/proc/4470/task/4470/fdinfo/4': No such file or directory du: cannot access `/proc/4470/fd/4': No such file or directory du: cannot access `/proc/4470/fdinfo/4': No such file or directory 0   /proc 5.0G    /root 212K    /run 7.8M    /sbin 4.0K    /selinux 4.0K    /srv 0   /sys 112K    /tmp 629M    /usr 2.3G    /var 0   /vmlinuz 8.1G    total   8.1G  total as usual. But I see cannot access rows, maybe problem because of them.  Then I checked the biggest folder in /. It is /root :  /# sudo du -sch /root/* 96K /root/Downloads 2.5G    /root/Dropbox 36K /root/nohup.out 4.0K    /root/npm-debug.log 4.0K    /root/readonly 980K    /root/redis-2.6.16.tar.gz 228M    /root/tmp 2.7G    total I've installed phpmyadmin sudo apt-get install phpmyadmin. Of course, I have also mysql and a web server running properly.  Now how can I reach it? I'm trying to write a shell script that, when run, will set some environment variables that will stay set in the caller's shell.  setenv FOO foo   in csh/tcsh, or  export FOO=foo   in sh/bash only set it during the script's execution.  I already know that   source myscript   will run the commands of the script rather than launching a new shell, and that can result in setting the "caller's" environment.  But here's the rub:  I want this script to be callable from either bash or csh.  In other words, I want users of either shell to be able to run my script and have their shell's environment changed.  So 'source' won't work for me, since a user running csh can't source a bash script, and a user running bash can't source a csh script.  Is there any reasonable solution that doesn't involve having to write and maintain TWO versions on the script? I have a complex embedded Linux software running on a gentoo derivative, on which a certain piece of code gets executed regularly every ~84 minutes. Sweeping through the main code to find places where this code might get executed was unsuccessful, and crontab also seems no possible explanation.   My question: Is it possible, by modifying the code in question, to find out which other process/code/file/service started it in the first place? Are there some information in the /proc directory I can use? Or is it impossible to find out the process that executed the given code? I think it would be very useful.  I have a question that I have an open bounty on. Putting up said bounty brought my reputation below the point where I am allowed to comment on other peoples' posts. It's so frustrating not to be able to comment and give feedback on the answers given!  Especially since it would be helpful, for them, me, and the readers, to know particularly what is good and isn't good about their answer, and therefore give some better guidelines to future answerers on how they can win the bounty. Word for a person who knows two or three languages A polyglot is a person who is fluent in many languages, but what do we call a person who is fluent in only two or three languages?  Is bi-glot a proper term for this?  I don't think the words bilingual / trilingual fit the bill, because I am looking for a -glot word. Word for "someone who talks too much" In the book Thomas's Calculus (11th edition) it is mentioned (Section 3.8 pg 225) that the derivative $dy/dx$ is not a ratio. Couldn't it be interpreted as a ratio, because according to the formula $dy = f'(x)dx$ we are able to plug in values for $dx$ and calculate a $dy$ (differential). Then if we rearrange we get $dy/dx$ which could be seen as a ratio.   I wonder if the author says this because $dx$ is an independent variable, and $dy$ is a dependent variable, for $dy/dx$ to be a ratio both variables need to be independent.. maybe? How to export and import mysql database with its data using php script?