I have just upgraded my system but it boots to Low Graphics mode by default. I have seen questions on how to solve this problem and they all suggest to run a couple of commands from a command-line interface.  But there isn't any command-line console by default in Low Graphics mode and hence, I cannot run those commands. And, the answers I saw to solve the problem doesn't explain this situation either.  How to switch to a command-line console in order to run the commands in Low Graphics mode?
Note: This is an attempt to create a canonical question that covers all instances of &quot;low-graphics mode&quot; error that occurs to a user, including but not limited to installation of wrong drivers, incorrect or invalid lightdm greeters, low disk space, incorrect installation of graphics card like ATI and Nvidia, incorrect configuration of xorg.conf file while setting up multiple monitors among others. If you are experiencing the &quot;low-graphics mode&quot; error when trying to login but none of the following answers work for you, please do ask a new question and then update the answers of this canonical question as and when your new question gets answered.   When I try to boot into my computer, I am getting this error:  The system is running in low-graphics mode Your screen, graphics cards, and input device settings could not be detected correctly. You will need to configure these yourself.   How do I fix the failsafe X mode and login into my computer?  Answer index:
In C the following horror is valid:  myFunc() {   return 42;  // return type defaults to int. }   But, what about in C++? I can't find a reference to it either way...  My compiler (Codegear C++Builder 2007) currently accepts it without warning, but I've had comments that this is an error in C++. When I make an animation, it always starts out slow, then speeds up, then slows down at the end.  I cannot figure out how to fix this. How to prove that a simple graph having 11 or more vertices or its complement is not planar? It is an exercise on a book again. If a simple graph $G$ has 11 or more vertices,then either G or its complement  $\overline { G } $ is not planar.  How to begin with this? Induction?  Thanks for your help! Is it (if at all) possible in Blender 2.6+?   If not, will future versions of Blender support it?  I see some old posts ( and ) saying that it is not possible. However, I found  referring to operators under  that allowed me to add sensors and controllers from python.  bpy.ops.logic.sensor_add(type='ALWAYS', object=my_obj.name) bpy.ops.logic.controller_add(type='LOGIC_AND', object=my_obj.name)   However I am not able to find any way to link them from python. I tried following (but did not work):  new_controller = my_obj.controllers[-1] new_sensor = my_obj.sensors[-1]   It throws AttributeError saying that object has no attribute 'controllers' :-/ I am recording videos on iPhone and uploading them to my Linux server. Users can see these videos on website. If users are seeing videos on mac or iDevices the video is looking fine but when users are seeing that video on windows systems these videos are getting rotated.   I am assuming this is because of some apple's flag in the recorded video which Windows systems are not able to read. Can I record videos in some way so they don't get rotated on Windows systems? Or is there any way I can re-encode videos with proper interface orientation using FFmpeg?  I am open to both FFmpeg or iOS way. XTerm only display part of some unicodes and Urxvt displays nothing In my case, (U)XTerm does display some unicodes, but only partially. For exmaple: for letters are: 𝒫φϕ𝒟. Here is a screenshot of UXTerm and Urxvt respectively   It seems that the problem is related to the letter space or letter length. By the way, everything is fine with gnome-terminal.  My current .Xresources file is: Xft.dpi:       120 Xft.antialias: true Xft.hinting:   true Xft.rgba:      rgb Xft.autohint:  false Xft.hintstyle: hintslight Xft.lcdfilter: lcddefault  XTerm*faceName:          Fixed XTerm*faceSize:          14 XTerm*reverseVideo:      false XTerm*selectToClipboard: true  UXTerm.vt100*faceName:          Fixed UXTerm.vt100*faceSize:          14 UXTerm.vt100*reverseVideo:      false UXTerm*selectToClipboard: true  URxvt.font:            xft:Fixed:pixelsize=18  URxvt.depth:                      32 URxvt.background:                 #222D31 URxvt*scrollBar:                  false URxvt*mouseWheelScrollPage:       false URxvt*cursorBlink:                true URxvt*background:                 black URxvt*foreground:                 grey URxvt*saveLines:                  5000  How to make XTerm and Urxvt to display those characters correctly? Is it possible? Fermat's Last Theorem for Gaussian Integers (excluding the integers or  same pure imaginaries) I am investigating solutions to Fermat's equation $$x^n + y^n = z^n$$ with $x,y,z$ in the Gaussian integers, excluding integers and pure imaginaries.  I have found out that there are only trivial solutions for the $n=3$ and $n=4$ cases, e.g. .   I would be grateful if you let me know of the current status or if it is already a theorem. In Illustrator is there a way to precisely scale to a pivot point or "reference point" that is off the screen? I mean when you want to zoom in somewhere far away from where you set that point and then scale precisely to align something.   Here's :     To scale relative to a different reference point , click where you   want the reference point to be in the document window, move the   pointer away from the reference point, and then drag until the object   is the desired size.   Well, I tried using this click-drag scaling method as well, but the level of precision is too low to be usable. It overshoots or undershoots the guide I'm aiming for.  The Scale tool's pop-up dialog isn't useful either. It only offers percentages. And moving/zooming are disabled while the dialog window is up, meaning I cannot navigate to the guide I need to see.  For these reasons, I need to be zoomed in on the guide, tweaking the measurements from the top Control Panel.  Some images to help illustrate what I mean:    ▲ The circle marks where I would like the center of my scale transformation to be.    ▲ Now zoomed in somewhere else, I am trying to get the black border of this bitmap image to align perfectly with the vector guide by scaling it.    ▲ I nudge the numbers in the Control Panel until the image is perfectly aligned.  One would think all would be perfect, but then I look and my reference point has vanished!   It seems the scaling has been executed relative to one of these limited nine reference point choices  instead of the reference point I specified.  There must be a way to scale precisely to a specific reference point in illustrator. Can somebody please enlighten me? How can I select part of a mesh and make it seperate? I want to make the teeth a separate child object from the mouth. I want to know the best way to do this.   I have tried going into edit mode with Tab and trying to select all the vertices but that doesn't move the teeth. Is there an easy way to select just that part and make it a separate child mesh to the rest of the mouth? "physical block size is 2048 bytes, but Linux says it is 512" when formatting USB - How to create a bootable USB without this error I was using:  dd  if=/path/to/my/ubuntuiso/ubuntu.iso  of=/dev/sdb1  bs=4M  &amp;&amp;  sync   In order to create bootable Ubuntu USB drives on older Ubuntu versions. It was working perfectly. Sometimes I used the Startup Disk Creator program, which  worked well.  But when I use the same methods on Ubuntu 16.04 LTS, I get some warnings while formatting it afterwards.   The installation media works as expected, but when I try to format that USB stick after my work is done, I get the following warning :    The partitioning of that Pendrive looks strange :    And it also shows my 16GB pendrive as 64GB.  After struggling a lot with Gparted, I will somehow format it. But Why is it happening like this ?? Is there any better methods of creating bootable Ubuntu in 16.04 ?  EDIT : there is a related question . But my question is not about how to format it properly. My question is "How to create a bootable USB without that errors." &amp; "Wht are the causes of that error" How to create a file system as a non root user? I'd like to create a filesystem image as a non-root user, the problem I'm facing is that the way I'm currently doing it, it needs a mount and as a non-root can't do a mount.  This is what I'm now doing:  #!/bin/sh  IMG="app.ext4" LBL="PIHU_APP" MNT="/mnt/PIHU_APP" APP="/home/buildroot/board/arctura/PIHU_APP/application"  #64MB: dd if=/dev/zero of=$IMG bs=4096 count=16384  mkfs.ext4 $IMG e2label $IMG $LBL  mkdir -p $MNT mount -o loop $IMG $MNT cp -r $APP $MNT sync umount $MNT   I have full root access, so I can setup/prepare anything, but the script will be executed from a non-root account.  However, I have a feeling there may be a better way that might not even need mounting, but I'm not sure.. Django set default form values I have a Model as follows:  class TankJournal(models.Model):     user = models.ForeignKey(User)     tank = models.ForeignKey(TankProfile)     ts = models.IntegerField(max_length=15)     title = models.CharField(max_length=50)     body = models.TextField()   I also have a model form for the above model as follows:  class JournalForm(ModelForm):     tank = forms.IntegerField(widget=forms.HiddenInput())       class Meta:         model = TankJournal         exclude = ('user','ts')   I want to know how to set the default value for that tank hidden field. Here is my function to show/save the form so far:  def addJournal(request, id=0):     if not request.user.is_authenticated():         return HttpResponseRedirect('/')      # checking if they own the tank     from django.contrib.auth.models import User     user = User.objects.get(pk=request.session['id'])      if request.method == 'POST':         form = JournalForm(request.POST)         if form.is_valid():             obj = form.save(commit=False)              # setting the user and ts             from time import time             obj.ts = int(time())             obj.user = user              obj.tank = TankProfile.objects.get(pk=form.cleaned_data['tank_id'])              # saving the test             obj.save()      else:         form = JournalForm()      try:         tank = TankProfile.objects.get(user=user, id=id)     except TankProfile.DoesNotExist:         return HttpResponseRedirect('/error/') From Berkeley Problems in Mathematics, Spring 1999, .  Let $f(x)\in \mathbb{Q}[x]$ be an irreducible polynomial of degree $n\ge 3$. Let $L$ be the splitting field of $f$, and let $\alpha\in L$ be a zero of $f$. Give that $[L:\mathbb{Q}]=n!$, prove that $\mathbb{Q}(\alpha^{4})=\mathbb{Q}(\alpha)$.   (BELOW IS NONSENSE, SHOULD BE IGNORED)  Following Gerry Myerson's advice, since $L$ is the splitting field of $f$, $L$ must be Galois over $\mathbb{Q}$. Thus the Galois group for $[L:\mathbb{Q}]=S_{n}$. Gerry now asserts that either $\mathbb{Q}(\alpha^{4})$ is of degree 2 over rationals or it must be $\mathbb{Q}$. But assuming this one can rule out the case $\mathbb{Q}$, since this would imply $\alpha$ is the root of a 4th or 2nd degree polynomial over $\mathbb{Q}$. But we know $n\ge 3$. So $\alpha$ must be the root of a 4th degree polynomial. We know $S_{n}$ has normal subgroups $A_{n}$ when $n\not=4$ and $V,A_{4}$ when $n=4$. I do not know how to proceed any further.   Now assuming $\mathbb{Q}(\alpha^{4})$ is a degree 2 abelian extension over $\mathbb{Q}$. We should have a chain of normal extensions $\mathbb{Q}(\alpha)\supset \mathbb{Q}(\alpha^{2})\supset \mathbb{Q}$. This would imply $S_{n}$ has a normal subgroup which has a normal subgroup. But we know $A_{n}$ for $n\ge 5$ are simple. So the only possibility is $\mathbb{Q}(\alpha)$ has a Galois group isomorphic to $V$. In this case $n=4$ as well. I can only proceed to here. Why don't Stack Exchange sites use a rich text editor? Why does the Stack Exchange network of sites use Markdown instead of some other rich text editor like FCKEditor or TinyMCE? Does it make sense to say, "The speed of light varies?"  Some may say right off the bat "Yes, it changes as a wave passes through a different medium."  However, I'd like to say no, because when I hear someone say the speed of light, I always think of the constant $c$ (unless the medium is specified to not be a vacuum, but then it isn't $c$ anymore), not the speed of a particular wave.  To me, it makes more sense to say something like, "The speed of a particular wave varies." What is the correct way to state this in the professional world? And in general, when professional physicists say "the speed of light," are they referring to the constant or the actual speed of the wave? MacBook Air: What taking up all my hard drive space Since I can't find any alternative to Linux'  elevation command, I have the following question:  How to define a PowerShell function which requires elevation? I mean UAC prompt.  Say, such function follows:  function system-check {     SFC /ScanNow }   System:  Windows 8.1 Pro 64-bit  PowerShell:   Major  Minor  Build  Revision -----  -----  -----  -------- 5      0      10586  117    EDIT1:  To be 100% understandable let me rephrase:   I run PowerShell as user I run the aforementioned function system-check I want the function to elevate in order to be able to execute the command; note, that I want the UAC prompt to appear Wrong kernel version returned by uname Ubuntu 16.04.1 LT uname -a returns:    Linux decebal-mobile 4.2.0-35-generic #40-Ubuntu SMP Tue Mar 15 22:15:45 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux   but E: Package 'linux-headers-4.2.0-35-generic' has no installation candidate  and my machine says linux headers version is at linux-headers-4.4.0-21-generic.   I have seen a similar problem described in a .  How can I update that? I am working on an Office 365 SharePoint online 2013. Now when I wanted to create a new private site collection, inside the online SharePoint admin center, I did not find the option to create new managed path, as I use to get when creating a site collection inside SharePoint on-premise. So how do I create a new managed paths inside SharePoint online? How to put an acute on an i using Biber: issues with "\'{\i}" I use some packages with require utf8. Here is the main file:  \documentclass[a4paper,titlepage]{report}  \usepackage[utf8]{inputenc} \usepackage[T1]{fontenc} \usepackage[american]{babel} \usepackage{csquotes} \usepackage[backend=biber,style=alphabetic]{biblatex} \addbibresource{refs.bib}  \begin{document} \nocite{*} \printbibliography[heading=bibintoc] \end{document}   And here is the reference file:  @MISC{Example,     author = {Author with spec\'{\i}al character},     title = {Title} }   I have no issues with composing special characters like \H{o} (ő) or \k{a} (ą). However, when I try to compose \'{\i} (í), I get the following inputenc error: "not set up for use with LaTeX". It seems like double compositions are not allowed. A solution is to use \'{i} instead, but not removing the dot is ugly. Surely there must be a better way?  Note: I have tried to add \DeclareUnicodeCharacter{00ED}{\'{\i}} to the preamble, but it doesn't help either.