After recently updating from 14.04 to 16.04, I tried to update to 18.04. However, when I try to do this, it keeps on failing presumably because of no disk space. When I click "Properties" on the "Computer" tab in "Files", it says that I have absolutely no free disk space, which I found strange because I transferred 40GB to a hard disk just before trying to update to 18.04 for the first time. I only just realized that memory could be a problem, but till now, I have tried to update to 18.04 multiple times.   When I do dpkg -l linux-headers-\* linux-image-\* | grep ^ii, I get the following, probably because I tried to update to 18.04 a lot of times:  ii  linux-headers-4.4.0-141             4.4.0-141.167        all          Header files related to Linux kernel version 4.4.0 ii  linux-headers-4.4.0-141-generic     4.4.0-141.167        amd64        Linux kernel headers for version 4.4.0 on 64 bit x86 SMP ii  linux-headers-4.4.0-142             4.4.0-142.168        all          Header files related to Linux kernel version 4.4.0 ii  linux-headers-4.4.0-142-generic     4.4.0-142.168        amd64        Linux kernel headers for version 4.4.0 on 64 bit x86 SMP ii  linux-headers-generic               4.4.0.142.148        amd64        Generic Linux kernel headers ii  linux-image-3.16.0-43-generic       3.16.0-43.58~14.04.1 amd64        Linux kernel image for version 3.16.0 on 64 bit x86 SMP ii  linux-image-4.4.0-141-generic       4.4.0-141.167        amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP ii  linux-image-4.4.0-142-generic       4.4.0-142.168        amd64        Linux kernel image for version 4.4.0 on 64 bit x86 SMP ii  linux-image-extra-3.16.0-43-generic 3.16.0-43.58~14.04.1 amd64        Linux kernel extra modules for version 3.16.0 on 64 bit x86 SMP ii  linux-image-extra-4.4.0-141-generic 4.4.0-141.167        amd64        Linux kernel extra modules for version 4.4.0 on 64 bit x86 SMP ii  linux-image-extra-4.4.0-142-generic 4.4.0-142.168        amd64        Linux kernel extra modules for version 4.4.0 on 64 bit x86 SMP ii  linux-image-generic                 4.4.0.142.148        amd64        Generic Linux kernel image   Is the existence of so many images and headers causing the memory full issue? If yes, how do I delete the proper ones?  The cause for the memory full issue is that my /var/log/cups/error_log is 86GB! Can I just delete this or is there a better and safer solution?
I have Lubuntu 16.10 installed on my disk mounted as /.  The problem is that the CUPS log file( /var/log/cups/error.log)  grows all the time until I no have free space left on the disk...   So when I delete that file, the space on disk freed up again  I already tried:    fsck disk usage analyzer every apt-cleaning/autocleaning, and dependencies fixing.    How should I proceed?  du -sxh:  9,0G    .  Model: ATA ST3160815AS (scsi) Disk /dev/sda: 160GB Sector size (logical/physical): 512B/512B Partition Table: msdos Disk Flags:   Number  Start   End     Size    Type      File system     Flags  1      32,3kB  50,3GB  50,3GB  primary   ext4            boot  2      50,3GB  160GB   110GB   extended  5      50,3GB  158GB   108GB   logical   ext4  6      158GB   160GB   2136MB  logical   linux-swap(v1)   parted --list &amp;&amp; sudo df -h:  Model: ATA ST3160815AS (scsi) Disk /dev/sda: 160GB Sector size (logical/physical): 512B/512B Partition Table: msdos Disk Flags:   Number  Start   End     Size    Type     File system  Flags  1      32,3kB  50,3GB  50,3GB  primary  ext4         boot  2      50,3GB  160GB   110GB   primary  ext4   Filesystem      Size  Used Avail Use% Mounted on udev            985M     0  985M   0% /dev tmpfs           201M  6,3M  195M   4% /run /dev/sda1        46G   43G  709M  99% / tmpfs          1003M  188K 1003M   1% /dev/shm tmpfs           5,0M  4,0K  5,0M   1% /run/lock tmpfs          1003M     0 1003M   0% /sys/fs/cgroup tmpfs           201M   36K  201M   1% /run/user/1000 /dev/sda2       101G   60M   96G   1% /media/aram/
Pending suggested edit message bug I just tried to edit a post on Stack Overflow but when I pressed the 'edit' button it showed me this message on a white page.    I know what the message means but I don't think it is supposed to show up in a white page. So, is this a bug or is it something else? Below is an attempt at a proof of the following problem. Any feedback would be greatly appreciated. Thx!  Let $E$ be a set and $O_n = \{x: d(x, E) &lt; \frac{1}{n}\}$. Show  If $E$ is compact then $m(E) = lim_{n \rightarrow \infty} m(O_n)$.  This is false for $E$ closed and unbounded or $E$ open and bounded.   Note that all sets are real and measurable refers to Lebesgue measurable.  Suppose $E$ is compact. Then $m(E) &lt; \infty$. Also, since each $O_n$ is an open set of $\mathbb{R}^d$, $m(O_n) &lt; \infty$. If either of the following is true, we have that $lim_{n \rightarrow \infty}m(O_n)=m(E)$: $O_n \nearrow E$ $O_n \searrow E$ Now  $\bigcap_{n=1}^{\infty} O_n = \{ x:d(x,E) = 0\}$. That is, $x \in \bigcap_{n=1}^{\infty}O_n \iff \exists n&gt; \frac{1}{\epsilon},\ n \in \mathbb{N} \iff x\in \{x \mid d(x,E) =0\}$. Then we have that $\bigcap_{n=1}^{\infty}O_n = E$ and $O_n \searrow E$. Thus $ \ m(E) = lim_{n \rightarrow \infty} m(O_n)$. Suppose $E$ is closed and unbounded. Let $E = \{(x,y): y = 2 \}$ and $O_n = \{(x,y): d(x,E) &lt; \frac{1}{n}\}$. Since $E$ is a line in $\mathbb{R}^2$, $m(E) = 0$. Also, since the measure of a rectangle in $\mathbb{R}^d$ is its volume, $m(O_n) = \left| O_n \right| = \infty$, since the rectangle $O_n$ is unbounded. It is therefore apparent that $m(E) \not = lim_{n \rightarrow \infty} m(O_n)$. Suppose $E$ is open and bounded. Let $E=(0,1)$ and $O_n = \{x \mid d(x,E) &lt; \frac{1}{n}\}$. $\mathbb{R}-E$ is closed and $O_n \in \mathbb{R}-E$. Since $\mathbb{R}-E$ contains all its limit points $lim_{n \rightarrow \infty}O_n = O \in \mathbb{R}-E$. Thus $lim_{n \rightarrow \infty} m(O_n) \neq m(E)$. At the end of a letter, is it correct to omit "I am" in this sentence?     I am looking forward to hearing from you   Then it will become:     Looking forward to hearing from you Can I charge my laptop with a charger that has different specifications? Basically on my site I have a bunch of song lyrics and in a static page I want to show them listed by album  and album position of the song and I have two custom fields with that data, sd_album_title and `sd_album_track_n. Plus some of the songs don't have an album yet, so both values are void, and I wish to list those ones at the foot of the others, sorted by alphabetical order.  The latest thing I tried at least to sort everything by the two field is this one:  $key = 'sd_album_title'; $themeta = get_post_meta($post-&gt;ID, $key, TRUE);  add_filter( 'pre_get_posts', 'my_get_posts' ); function my_get_posts( $query ) {     if ($themeta != '') {         $query-&gt;set( 'post_type', 'lyric' );         $query-&gt;set( 'meta_key', 'sd_album_title' );         $query-&gt;set( 'orderby', 'meta_value' );         $query-&gt;set( 'order', 'ASC' );         $query-&gt;set( 'meta_query', array(               array(                     'key' =&gt; 'sd_album_title'               ),               array(                     'key' =&gt; 'sd_album_track_n',                     'value' =&gt; 'target_value',                     'compare' =&gt; '&gt;=',                     'type' =&gt; 'numeric'               )         ));     }     return $query; }  $getlist= 'my_get_posts'; $posts = get_posts( $getlist );   And my intention was to put an else at the end of it with an array ordered by title for the other songs, but it returns nothing as it is. Could something like this work with some corrections or am I on a totally wrong path? How widely-accepted is "What do you got?" to Americans? Watching , I noticed that Melanie Griffith twice asked    I recognise this as an American construction which sounds strange to me — Brits invariably say either "What have you got?" or "What do you have?". But I'd be interested to know if it's considered "normal" by most/all Americans, or if it's regionally or otherwise restricted. Where does the energy required to stop a moving body come from and go? For a long time, I have been thinking about this: In order to stop a moving body, I have to apply impulse to change the existing momentum to $0$. For the impulse I have to impart force on the moving body . That means I have to eliminate all the kinetic energy associated with the moving object in order to bring it to a halt. Thus, work is done on the object, right? If work is done, energy must be given by me...  Here is where my confusion arises:   If I eliminate the associated kinetic energy of the body, where does this energy go? The work(?) done by me on the moving object to stop it obviously uses energy from me. Again, where does this energy go? How to get access to USB-storage from an application installed as Snap? I have Ubuntu 18.04 LTS installed. I inserted USB-flash to my laptop. It was automounted to /media/username/DISKLABEL and opened in Nautilus. I can read and write objects to it. How can I access it from the application, which is installed as Snap? I tried snaps of the following applications such as gedit, arduino-mhall119, organize-my-files. All them show me errors if I navigate to /media folder:    Could not read the contents of Media Error opening the directory of '/media': permission denied  Output of active Snap  is below: $ snap interfaces  | grep -v &quot;.*-$&quot; Slot                             Plug :browser-support                 organize-my-files :core-support                    core:core-support-plug :cups-control                    gedit :desktop                         gedit,organize-my-files :desktop-legacy                  gedit,organize-my-files :gsettings                       gedit,organize-my-files :home                            arduino-mhall119,gedit,organize-my-files :network                         arduino-mhall119,gedit,organize-my-files,pulsemixer :opengl                          organize-my-files :pulseaudio                      organize-my-files,pulsemixer :unity7                          arduino-mhall119,gedit,organize-my-files :wayland                         gedit :x11                             arduino-mhall119,organize-my-files,pulsemixer gnome-3-26-1604:gnome-3-26-1604  gedit gtk-common-themes:gtk3-themes    gedit gtk-common-themes:icon-themes    gedit gtk-common-themes:sound-themes   gedit -                                arduino-mhall119:serial-port -                                gedit:avahi-observe -                                gedit:mount-observe  Updates:  connecting mount-observe to Gedit with snap connect gedit:mount-observe does not help. it seems that we need special Snap with support of  interface. Georeferencing old map in QGIS? I have an old map over a part of Laos and wondering how do I georeference the map with the help of the Grid lines and other Longitude and Latitude information on the scanned map? I have searched for information on the internet and tried many times. My scanned map wont overly correctly on the base map. Any base map would be fine. As long as I can check the result.  Do I add X/East and Y/North values from the grid line crossings as marked and written in some parts of the map? How do I begin georeferencing this map? Do I have to add zeros after the two digits? For example if the Easting is 24 (its in KM right? Do I add like three/four zeros to convert it to meters?  I georeferenced the map with the option "From Map Canvas" in the georeferencer tool and I succeeded but I want to know the coordinate of a point on my old scanned map and write them as X/East and Y/North to georeference the map.   I hope I am not babbling and someone understands what I mean!  We can set the CRS to WGS84, EPSG:4326. From what I know, it is unknown whether $x_n=x_{n-1}^2 + 1$ has a closed form. Is there a recurrence relation which is known to have no closed form with a proof of inexistence?  Assuming a closed form is a non recursive description using the elementary operations of addition multiplication and power, or, assuming any other good definition of "closed form".  Edit  There are similar questions out there, but the answers are a little bit going around the question.   So is there one with proof or is it unknown? And if it depends on the definition of a closed form, then what are the (or some) options? How strong can a closed form definition be to still have a recursive relation that can be proved to not being able to have its form?  Update  Because it is a big question, and I don't want to open a new small one, I think a good representative small question about this subject is:  Is there a recurrence relation with a domain of the natural numbers, described by elementary functions, which has no closed form defined as:  A closed form of a recurrence relation with a domain of natural numbers is a function $f$ that can be described as a composition of a constant number of elementary functions without reccursion. i.e, $f(n) = f_1(f_2( \dots (f_k(n))) \dots) $ where $f_i$ is elementary for all $1 \leq i \leq k$   I think this definition is the most intuitive and basic.  For example, the relation $x_n = x_{n-1}+1$ has a closed form in this sense: $$f(n) = f_1(f_2(f_3(f_4(n))))$$  Where $f_1$ is division, $f_2(n)=(n,2)$, $f_3$ is multiplication and $f_4(n) = (n,n+1)$   Is there a recurrence relation which has no closed form in this sense? Setting up LVM Snapshot as a backup/restore point in ubuntu. Why? Well, as I see it, with all the great usefulness of Linux, its biggest drawback is with its mixed up way of installing apps. All the dlls go to one directory. All the configuration files to another. And the binaries are also put in a bunch. Yes, Windows works the same way more or less, but with the nature of system/server software installed on Linux, being that most of the software installed is only about 95% mature at any given time, messing up your system twice a month is very probable.. Of course, we can backup the system before and after each installation, but that takes a million years. System backups (as oppose to just data/files backup) requires you to turn off you computer and use some form of bootable live CD and a backup media. And, if the drive is more than 15% full, it might take a long time to do the backup, even with modern hardware. So, how can this be done? Best compiler warning level for C/C++ compilers? Should I load an entire html page with AJAX? sum of double precision gives weird results I have a range and need to sum it using SUM function but the result is N/A if there is any N/A value. How can I make the SUM function to treat the N/A value as 0 value?  Please help! Redirect output from all commands to file, not just last Is there a way to "hide" a normal windowed application in Windows?  I'm looking for something that removes it from the taskbar and possibly puts an icon in the system tray instead. I know that the derivative of the inverse function of $f(x)$ is $g'(y) = \frac{1}{f'(x)}$ But how to derive the formula for the second derivative of g(y) knowing that $\left[\frac{1}{f(x)}\right]' = -\frac{f'(x)}{(f(x))^2}$ ?  I just started studying this chapter, so please try to be as simple as possible ;-) Thank you. Open Attachment on Create of Child Record Why don't electromagnetic waves require a medium?