I'm new to dual boot and don't know much about it. I installed Ubuntu 18.04.2 on a USB key and booted from it (I chose the UEFI option). My computer has 3 hard drives (one 250 Gb SSD with Windows, one 2Tb HDD with games and one 1Tb SSD with nothing on it. This one was completely "unalocated"). When installing Ubuntu, it only showed the option to erase disk. I picked that and selected the 1TB empty SSD. I completed the installation.   Now, I have several problems.  1) My computer boots directly to Ubuntu. To boot on Windows, I need to press F12 and choose to boot from the 250 Gb SSD. I tried to install grub, then did a reboot but it didn't change anything. I tried to install boot-repair, but I get the error  "GPT detected. Please create a BIOS-Boot partition (>1MB, unformatted filesystem, bios_grub flag). This can be performed via tools such as Gparted. Then try again.". I don't know what to do now and I'm afraid to srew things up beyond repair.  2) I have a GTX 2080 and a i9-9900k. Ubuntu doesn't recognize the graphics card so I get very weird graphical issues (also my 2nd monitor isn't recognized). I tried to install nvidia drivers but it didn't work. Apparently this has something to do with removing "secure boot" ?
Since I updated Windows to 8.1 my Grub menu disappeared. I ran Ubuntu using Live USB, I used Boot-Repair but something went wrong. If I click on Reccomended repair I get this error:     GPT detected. Please create a BIOS-Boot partition (>1MB, unformatted filesystem, bios_grub flag). This can be performed via tools such as Gparted. Then try again. Alternatively, you can retry after activating the [Separate /boot/efi partition:] option.   So I tried to set my sda9 (I think that it's the Ubuntu system partition, since it's ext4) with the bios_grub flag and then to run Boot-Repair again. It didn't work.  I don't know what to do. My Grub was working fine (using UEFI) before I updated Windows.  I removed the bios_grub flag. Then I used fsck and it didn't find any error. So I tried again with Boot-Repair but it always gives me the "GPT detected" error. My boot is on UEFI mode, Secure Boot is "off".  When I boot my PC with SecureBoot OFF, I can reach the GRUB menu. But it's empty (the only voice is "System Setup").  I mounted my Ubuntu system disk:  sudo mount /dev/sda9 /mnt   and the other things:  sudo mount --bind /dev /mnt/dev sudo mount --bind /proc /mnt/proc sudo mount --bind /sys /mnt/sys   I logged on the system with chroot:  sudo chroot /mnt   I re-installed grub:  grub-install /dev/sda update-grub2   But it still doesn't work.
Postfix Connection Timed out I used the  tutorial below to setup postfix and dovecot on a Digital Ocean server. But I'm getting "Connection Timed out" when postfix/smtp tries to deliver an email to a remote host like gmail or yahoo..      RECEIVING A NEW MESSAGE /var/log/mail.log    Feb 2 22:33:38 localhost dovecot: auth-worker: Debug: Loading modules from directory: /usr/lib/dovecot/modules/auth  Feb 2 22:33:38 localhost dovecot: auth-worker: Debug: pam(app,189.63.49.XXX): lookup service=dovecot  Feb 2 22:33:38 localhost dovecot: auth-worker: Debug: pam(app,189.63.49.XXX): #1/1 style=1 msg=Password:   Feb 2 22:33:38 localhost dovecot: auth: Debug: client out: OK#0111#011user=app  Feb 2 22:33:40 localhost postfix/submission/smtpd[1045]: E9AA724264: client=unknown[189.63.49.XXX], sasl_method=PLAIN, sasl_username=app  Feb 2 22:33:43 localhost postfix/cleanup[1052]: E9AA724264: message-id=  Feb 2 22:33:43 localhost postfix/qmgr[32661]: E9AA724264: from=, size=485, nrcpt=1 (queue active)  Feb 2 22:33:45 localhost postfix/submission/smtpd[1045]: disconnect from unknown[189.63.49.XXX]  Feb 2 22:34:14 localhost postfix/smtp[1053]: connect to mta5.am0.yahoodns.net[98.136.216.25]:25: Connection timed out    Feb 2 22:24:21 localhost postfix/smtp[1013]: connect to mta6.am0.yahoodns.net[98.136.217.202]:25: Connection timed out  Feb 2 22:24:21 localhost postfix/smtp[1014]: connect to gmail-smtp-in.l.google.com[173.194.76.27]:25: Connection timed out  Feb 2 22:24:21 localhost postfix/smtp[1015]: connect to gmail-smtp-in.l.google.com[173.194.76.27]:25: Connection timed out  Feb 2 22:24:21 localhost postfix/smtp[1012]: connect to aspmx.l.google.com[173.194.68.27]:25: Connection timed out    Here is /etc/postfix/main.cf   /etc/postfix/master.cf   Result from #> netstat -nlptu What is the "canary thread" and why is it starving? I've got a simple Leaflet map with a basemap and one map-layer coming from my own hosted GeoServer.  I made the layers show up nicely in a map.  Now I want to add popups on the point layer showing information stored in MapService.  I couldn't find too much information about that topic.   There's one link to a working example but the link seems to be broken. I found another example which I addopted. You can see it on . I'd like to display the content of the name field in the attribute table but nothing happens when the user clicks the map.  Any idea? When and why will a compiler initialise memory to 0xCD, 0xDD, etc. on malloc/free/new/delete? I know that the compiler will sometimes initialize memory with certain patterns such as 0xCD and 0xDD.  What I want to know is when and why this happens.  When  Is this specific to the compiler used?  Do malloc/new and free/delete work in the same way with regard to this?  Is it platform specific?  Will it occur on other operating systems, such as Linux or VxWorks?  Why  My understanding is this only occurs in Win32 debug configuration, and it is used to detect memory overruns and to help the compiler catch exceptions.  Can you give any practical examples as to how this initialization is useful?  I remember reading something (maybe in Code Complete 2) saying that it is good to initialize memory to a known pattern when allocating it, and certain patterns will trigger interrupts in Win32 which will result in exceptions showing in the debugger.  How portable is this? Why is it called Area 51? According to : "We like the little aliens."  This seems well targeted to appeal to the Stack Overflow / Server Fault / Super User audience, but way off the mark if the goal is to "make the Internet a better place to get expert answers to your questions."    There are experts who aren't interested in or focused on technology oriented topics.  Little aliens are unlikely to be something that someone interested in organizing a site on gardening would gravitate too.  No, I'm not suggesting that no one interested in gardening would be bother to look at a site with little aliens, but won't it be likely that the sort of mass appeal to to a very broad cross section of the internet will be lacking? How make f[{x,y}] evaluate as f[x,y]? I ran dolphin like this:  dolphin . &amp;   I see messages in the console like these:  QPixmap::scaled: Pixmap is a null pixmap   How can I keep the console clean or silent? on proving bac-cab rule, $\vec{A} \times ( \vec{B} \times \vec{C})= \vec{B} (\vec{A} \cdot\vec{C})- \vec{C}(\vec{A}\cdot\vec{B})$ I noticed something when I was doing a proof of the BAC-CAB rule, and wanted to check if my intuition was correct.   First, when I actually multiplied out $\vec{B} (\vec{A} \cdot\vec{C})-\vec{C}(\vec{A}\cdot\vec{B}) $ I noticed that I got the same thing. That is, the two quantities are equal. This makes sense since they are dot products. But that further implies that the expression goes to zero.  Well, that means that $\vec{A} \times (\vec{B} \times \vec{C})$ would have to be zero too. And when I thought about it it occurred to me that $\vec{B} \times \vec{C}$ describes a vector perpendicular to both B and C; it's orthogonal. But $\vec{A} \times$ (any vector) will describe a vector perpendicular to (any vector) and in this case, that's $\vec{B} \times \vec{C}$. That is going to be parallel with the vector described by $\vec{B} \times \vec{C}$ itself and that further implies that the cross product of the two is equal to zero. Which is equal to the BAC-CAB quantity above.   So, what is the big honking flaw in my reasoning here? :-) The extension of smooth function Compact topological space with closed graph implies continuity Let $X,Y$ be topological spaces and $f:X \rightarrow Y$  If $Y$ is compact and $G(f)$ (graph of $f$) is closed, show that $f$ is continuous.   I consider an open set in $X$, and as $G(f)$ is closed, $(X \times Y)-G(f)$ is open. And I guess I need to do something here. Then I can get some open sets. Also, I notice that compact is something relate to "finite". I guess I can use the compactness to do finite intersection or union and get the result finally.  But what should I do in the middle or I am not even on a right track. Searching through ODT documents without opening them? Let's say I have 2000 .ODT files. Their names are random numbers. How do I go about searching for, let's say, "pricing list"? How do I find the document I need without opening all of them one by one and checking to see if it's the right one?  Is there some program to search through the words in the documents without opening them? Using matplotlib in pygame Show that $a^{q-1} \equiv 1 \pmod{pq}$ Assume that $p$ and $q$ are distinct add primes such that $p-1\mid q-1$. If $\gcd(a,pq)=1$ ,show that: $$a^{q-1} \equiv 1 \pmod{pq}$$   I have tried as follows: $$a^{q-1} \equiv 1 \pmod{q} \quad \text{and} \quad a^{p-1} \equiv 1 \pmod{p}$$ $$\implies a^{(q-1)(p-1)} \equiv 1 \pmod{q} \quad \text{and} \quad a^{(q-1)(p-1)} \equiv 1 \pmod{p}$$ $$\implies a^{(q-1)(p-1)} \equiv 1 \pmod{pq}$$ But then I am stuck - please help. What is the most "pythonic" way to iterate over a list in chunks? I have a Python script which takes as input a list of integers, which I need to work with four integers at a time.  Unfortunately, I don't have control of the input, or I'd have it passed in as a list of four-element tuples.  Currently, I'm iterating over it this way: for i in range(0, len(ints), 4):     # dummy op for example code     foo += ints[i] * ints[i + 1] + ints[i + 2] * ints[i + 3]  It looks a lot like &quot;C-think&quot;, though, which makes me suspect there's a more pythonic way of dealing with this situation.  The list is discarded after iterating, so it needn't be preserved.  Perhaps something like this would be better? while ints:     foo += ints[0] * ints[1] + ints[2] * ints[3]     ints[0:4] = []  Still doesn't quite &quot;feel&quot; right, though.  :-/ Related question: What is wrong with "Where should this car be parked?"? I have a MicroSD card in a USB adapter (which plugs into a USB port on my machine, and acts like a USB flash drive). I was using Unetbootin to make this a bootable USB flash drive with Kubuntu. But I needed to cancel while it was working. So I killed the Unetbootin process from the console.  Since then, I can't format the MicroSD or delete the folder that Kubuntu made. I have also tried mkdosfs, with no success. I can't mount the drive anymore either? What can I do to make this drive usable again?  Trying to create a new partition table in GParted, as described in Eliah Kagan's answer, does not work. It fails with the error message "imposible crear tabla de particiones" ("unable to create a partition table"). I have a series of ranges with start dates and end dates. I want to check to see if a date is within that range.  Date.before() and Date.after() seem to be a little awkward to use. What I really need is something like this pseudocode:  boolean isWithinRange(Date testDate) {     return testDate &gt;= startDate &amp;&amp; testDate &lt;= endDate; }   Not sure if it's relevant, but the dates I'm pulling from the database have timestamps. Getting incorrect slope values from an ASTER DEM in QGIS? Set the size of pgf picture? I have a pgf picture which I insert with:  \input{m1.pgf}   But the image is too big. Instead of regenerating a smaller image, I'd rather take advantage of vector graphics, and have XeLaTeX scale it. How do I set the width of pgf picture (keeping its aspect ratio)?  MWE  tex:  \documentclass{article}  \usepackage{fontspec} % enagles loading of OpenType fonts \usepackage{polyglossia} % support for languages  % fonts: \defaultfontfeatures{Scale=MatchLowercase,Mapping=tex-text} % without this XeLaTeX won't turn "--" into dashes \setmainfont{DejaVu Sans} \setsansfont{DejaVu Sans} \setmonofont{DejaVu Sans Mono}  % pgf: \usepackage{pgf}  \begin{document}  \input{m1.pgf}  \end{document}   Sample pgf:  (it's too big to cite it here, and I can't make much smaller). After finishing The Cayo Perico Heist, how long will it be set in hard mode? After I finished The Cayo Perico Heist, I tried setting up another heist in the Kosatka, and got this message :  The setup cost for The Cayo Perico Heist is $25000. Setting up now will set the heist to Hard Mode. Do you wish to proceed?  It seems that there is a cooldown period before the heist reverts to normal mode from hard mode. How long will it take before it reverts to normal mode? Also, does the cooldown timer run even if you're logged out of GTA Online? E.g., if I quit GTA Online just after finishing the heist, the next time I log back in, will I have to wait for the cooldown period to finish before it reverts to normal mode?