In  someone thanked me for an edit, and I could have sworn that I responded. Later, I could not find my own comment, which only said "You're welcome." So I posted it (again?). Then I was wondering if it was removed by a moderator, and if such comments are discouraged, so I thought I would ask here for a straight answer.  The comment looks like this:  @TLP Thanks for the "\@"; that's an important fix. – chepner  You're welcome. – TLP    Personally, I think one should answer "thanks" with "you're welcome", because, well, that's just basic courtesy, and leaving that out makes me feel uncomfortable. And I would think that it also would be noticed by people who give thanks.  Also as a side note, if a comment is removed by moderator, it would be nice to be notified about it somehow, so as to clarify that I did something wrong, and what it was. (And why, preferably)  Update: To clarify, this is not a "long term" question, if someone deletes the comment a day or so later, and the person it was sent to has read it, that is fine.
There have been a number of cases where I would like to thank someone for providing me with a thorough response and give them feedback beyond the vote up. Often I wish people would tell me why they voted me up. Not that the thank you part is necessary but it sets it apart from the other comments related to answering the question itself.  In this type of situation is a "Thank you" acceptable in a comment?     For more information, see  in the .
Busy Device on Umount I often experience a problem to umount a directory:  umount /mnt/dir umount: /mnt/dir: device is busy   There are many reasons why the device is busy. Sometimes there are processes running which have open locks on it, sometimes there are other directories mounted on top of /mnt/dir.  My question:  What are the steps to check why a directory couldn't be unmounted.  I know there are many reasons, but it's ok if you explain a specific solution.  [EDIT]  [X]  running processes on mounted volumes.   [X] another volume is mounted on top of a volume we want to unmount   [_] NFS locks the volume we want to unmount Electrolytic Capacitor Voltage Rating vs capacitance I have always believed that it was ok to replace a capacitor with a slightly higher voltage rated one. eg 16v with 25v.Going higher than this would risk the capacitance value being out at the working voltage. However I just read the following quote from this       Electrolytic capacitors are non-ferroelectric with a very low dielectric constant. Their capacitance is derived from a very high surface area and nanometer thick dielectric layers. Their capacitance is not a function of applied voltage.‐Design Solutions For DC Bias In Multilayer Ceramic Capacitors (August 2010 Electronic Engineering Times)   So does this rule not apply to aluminum electrolytics? Eg will I have no issues replacing an electrolytic 25v 100uf with a 50v 100uf assuming both are low esr, similar footprint and good quailty? Prime spectrums bijection but not homeomorphism Rm can't delete file If $a$ divides $bc$ and $\gcd(a,b) = d$ then $\frac a d$ divides c I'm trying to prove that if $a$ divides $bc$ and $\gcd(a,b) = d$ then $\frac a d$ divides c. I tried using Bezout identity but couldn't get anywhere. Many to Many and Weak Entities I have an entity that cannot exist without being defined by another, and I want this entity to participate in a many-to-many relationship.  Example: An artist has an album (the album cannot exist without an artist), the album also has many tracks, but the same track can exist in many albums.  So we have a many-to-many relationship between the album and the tracks.  If the album is a weak entity, then its primary key is a foreign key referencing the artist, thus it cannot be a foreign key to another table representing a many-to-many relationship.  The question is: is it possible to have this kind of relationship in SQL, and if so, how do I express it? Lets say I'm building a base class which will be extended upon by the children class. So a base class is called Base and children can be Child1, Child2, etc.  In the base class's constructor, how can i get the value of Child1/Child2?  This is all using PHP Which site deals with career development questions for programmers? Is there any site in the network where career development questions about the programming profession can be asked ? I thought Programmer's was the site for it, but that doesn't appear to be the case. Is there a modal command for MakeLowercase? Analog to  question I've been wondering WHAT is to \lowercase as \bfseries is to \textbf? (... and for uppercase, or \MakeLowercase and MakeUppercase, etc., which also seem to be text-block commands as explained .)  Is there a "switch"/"declaration"/"modal command" (what is the correct term here?, is there a difference between them?) that would allow one to turn something into lowercase/uppercase in the same way that one would use \scshape for example, i.e., not as text-block command with the curly braces?  Or how to create such a command?  I couldn't find any clue on the forum. Good text on Clinical Trials? I'm an undergraduate statistics student looking for a good treatment of clinical trials analysis. The text should cover the fundamentals of experimental design, blocking, power analysis, latin squares design, and cluster randomization designs, among other topics.   I have an undergraduate knowledge of mathematical statistics and real analysis, but if there's a fantastic text that requires a bit higher level of statistics or analysis, I can work up to it. How can you combine all lines that end with a backslash character? Using a common command line tool like sed or awk, is it possible to join all lines that end with a given character, like a backslash?  For example, given the file:  foo bar \ bash \ baz dude \ happy   I would like to get this output:  foo bar bash baz dude happy Given this XML, what XPath returns all elements whose prop attribute contains Foo (the first three nodes):  &lt;bla&gt;  &lt;a prop="Foo1"/&gt;  &lt;a prop="Foo2"/&gt;  &lt;a prop="3Foo"/&gt;  &lt;a prop="Bar"/&gt; &lt;/bla&gt; Examples of involutions on $\mathbb{R}$ Just recently I read up something about involutions (functions $f: A \rightarrow A$ such that $f(f(x))=x$, for all $x$ in the domain of $f$), and was wondering how many (if there is a small set of general functions) such involutions exist for $A = \mathbb{R}$, or maybe $A = \mathbb{R} - S$, where S is some set of points that would make the involution work if they were left out of $A$. In general I'm interested in real functions that are involutions, continuous or otherwise.  There were some examples I found , but any more would be certainly very interesting! Was the blue fire from Crimes of Grindlewald Fiendfyre? In Crimes of Grindlewald, Grindelwald uses a powerful blue flame that takes on the shape of monsters. Was this Fiendfyre? Do I need Intel Smart Response when installing Ubuntu? With lots of guides and setup variations all over the internet, I find it confusing which is which to really follow. Normally, in Windows 8 my setup would be install everything in the HDD and use Intel Smart Response for a speedy setup. However as I am new to Linux I really don't know what to do.  My ideal setup would be something similar to this, but I know for a fact that IRST is not available in Linux so what I intend to do is keep the OS files in the SSD instead and keep my media on the larger HDD. A step by step procedure would be extremely helpful.     Edit: I want a system running solely on Ubuntu, with the SSD to speed things up but setting it in such a way that it does not hasten its lifespan.    # /etc/fstab: static file system information.  # # Use 'blkid' to print the universally unique identifier for a  # device; this may be used with UUID= as a more robust way to name devices  # that works even if disks are added and removed. See fstab(5).  #  # &lt;file system&gt; &lt;mount point&gt; &lt;type&gt; &lt;options&gt; &lt;dump&gt; &lt;pass&gt;  # / was on /dev/sda1 during installation  UUID=80289460-5983-4349-8afc-6f3119938ee9 / ext4 errors=remount-ro 0 1   # /files was on /dev/sdb5 during installation  UUID=c1678c88-5100-41bc-8090-7887f1622c7f /files ext4 defaults 0 2   # swap was on /dev/sdb6 during installation  UUID=608e3ec2-c76e-4657-af6d-80793b5f50f6 none swap sw 0 0 lstlisting: how to set code color and frame color How do I protect random people pointing their domain to my server? How can I respawn the Ender Dragon? I have a server and the Ender dragon has been defeated.  However, returning to The End does not respawn the Ender Dragon.  How can I get the final boss back on a vanilla server without using mods? Custom thumbnailers don’t work on Ubuntu 18.10 and 18.04 Recently I had a bunch of my own scripts for the thumbnails in Nautilus: , , office documents and so on.  Seems like either I’m doing something wrong (thumbnail generation behavior changed), or custom thumbnailes don’t work in latest GNOME at all, even my previous scripts, which worked smoothly on previous versions of Ubuntu.  I’ve done some research, tried to run a simple script (see below) and it didn’t work out.  My test thumbnailer in /usr/share/thumbnailers/z.thumbnailer:  [Thumbnailer Entry] Exec=/home/maximal/thumb.sh %s %i %u %o MimeType=image/webp;image/x-webp   Where /home/maximal/thumb.sh is:  #!/bin/bash echo $0 &gt;&gt; /home/maximal/thumb.log echo $1 &gt;&gt; /home/maximal/thumb.log echo $2 &gt;&gt; /home/maximal/thumb.log echo $3 &gt;&gt; /home/maximal/thumb.log echo $4 &gt;&gt; /home/maximal/thumb.log   Then, when I remove thumbnail cache rm -rf ~/.cache/thumbnails and restart Nautilus nautilus -q, my log file doesn’t contain anything and ~/.cache/thumbnails/fail/gnome-thumbnail-factory contains all the failed thumbs (looks like corrupted/empty PNGs):    So, apparently, Nautilus even didn’t try to execute my thumbnailer script. When I try to run thumb command itself, it works perfectly. For example convert through cwebp|dwebp package:  convert -thumbnail 256x256 file.webp png:file.webp.png   When I wrap this command to a thumbnailer, it looks like it wasn’t even requested to run by Nautilus.  [Thumbnailer Entry] Exec=convert -thumbnail %sx%s %i png:%o MimeType=image/webp;image/x-webp;   Exactly the same situation occurs with other my thumbnailers: audio waveforms, office documents, photoshop files and so on.  Could anyone help? How can I switch a 32-bit installation to a 64-bit one? I've got a 32-bit Ubuntu installation running on 64-bit hardware. Now that , I would like to switch to 64-bit without having to reinstall the OS.  This is one of the :  Shawn installed his system using the 32-bit version of Ubuntu, but his hardware is 64-bit and he wants to switch over. He manually installs the amd64 versions of dpkg and apt, replacing the i386 versions and changing which architecture is used as the default; then he installs the amd64 ubuntu-minimal package; then he installs the amd64 ubuntu-desktop package. Over time the remaining i386 packages are replaced automatically on upgrade.  However, when trying to follow the instructions in there, I cannot find any 64-bit version of dpkg or apt.  Did this user story got implemented in a different way in the final spec, or do I need to do something differently?  In short, how can I switch my 32-bit installation to 64-bit?