How to find (as grouped) the directory who is taking all the disk spaces?  # df -h Filesystem      Size  Used Avail Use% Mounted on /dev/vda1        60G   54G  6.4G  90% / devtmpfs        1.4G     0  1.4G   0% /dev tmpfs           1.4G     0  1.4G   0% /dev/shm tmpfs           1.4G  161M  1.3G  12% /run tmpfs           1.4G     0  1.4G   0% /sys/fs/cgroup tmpfs           285M     0  285M   0% /run/user/0   It does not help to see /dev/vda1 is 90%, how to check which directories having the largest disk reserve?  example:  /var/log/httpd    20GB /var/log/pluto    10GB /var/log/syslog    5GB /var/log/tcpdump   1GB /...              restGB
What is the command to find out how much disk space is being used/remaining?
MySQL SELECT LAST_INSERT_ID() for compound key. Is it possible? Can I get the LAST INSERT ID() for a compound key in MySQL? Do parts of a hash carry the properties of the entire hash? When I need to generate unique id's based on some information hashing is typical choice. However, sometimes that id needs to be of a particular size.  I've seen a lot of schemes (HMAC-MD5-96 in SSH, CGA in SeND for IPv6) that use a portion of a hash, so I'm thinking it might be alright to use it that way.    Which properties of a hash are preserved and which do not apply anymore?  Obviously, with less bits, the chance of collision goes up, but can I still rely on the partial hash for uniform character distribution?  What about the ?  I'm guessing that if a hash modifies the entire hash upon the smallest change to the input, that would imply that a portion of that hash would be equally well changed.  Am I thinking about this correctly?  Also, would these behaviors be different for different hashing algorithms? Given $f(x) = x + |x|$ for what values of $x$ is $f$ differentiable How do I share a private YouTube video with someone? I have uploaded a YouTube video and marked it as private.  Now I want to share it with someone. I have tried to share it a few times, but they have not received any email notification.  What is the proper way of sharing the video? What's the difference between $\mathbb{R}^2$ and the complex plane? I haven't taken any complex analysis course yet, but now I have this question that relates to it.  Let's have a look at a very simple example. Suppose $x,y$ and $z$ are the Cartesian coordinates and we have a function $z=f(x,y)=\cos(x)+\sin(y)$. However, now I change the $\mathbb{R}^2$ plane $x,y$ to complex plane and make a new function, $z=\cos(t)+i\sin(t)$.  So, can anyone tell me some famous and fundamental differences between complex plane and $\mathbb{R}^2$ by this example, like some features $\mathbb{R}^2 $ has but complex plane doesn't or the other way around. (Actually I am trying to understand why electrical engineers always want to put signal into the complex numbers rather than $\mathbb{R}^2$, if a signal is affected by 2 components)   Thanks for help me out! Calculus book recommendations (for complete beginner) Well I have not started calculus yet but I am really keen to. I would love if you suggest some books.  Points to be noted:   I really don't like the way textbooks are written so please no "textbooks"  I am COMPLETELY beginner in calculus. I know a little bit of trigonometry and what functions are but not really in depth.The book should start from the base, I mean really from the base. I may require a precalculus book too if the books don't cover that. I would really love if the book shows how calculus was developed, why it was developed and things like that.   Well,thanks in advance! What does 'close invalidated' mean Recently I flagged  as a duplicate. A few days later, when I checked it again to see if it was closed, I realized it wasn't.    Searching in Meta brought me to , where a comment suggested checking the timeline. So I checked the  and saw that the close flag was set as invalidated.  Does this mean that it was disputed? When I click on it I see only "This item is no longer reviewable." Do I need more reputation (3000+ ?) to view more detailed information? What are the advantages/disadvantages of the new encryption feature in ubuntu 13.10 I'm in the middle of installing 13.10 and the Ubuntu page I was following on how to install from a USB stick says nothing about these two choices (on the Installation type screen):     1) Encrypt the new Ubuntu installation for security (you will choose a security key in the next step).      2) Use LVM with the new Ubuntu installation (this will set up Logical Volume Management. It allows taking snapshots and easier partition resizing)   I'm a writer using the computer for mostly writing ebooks but I also do all the things most people do: buy stuff online, online banking etc. I want my information to be safe but I don't want to overburden my system with security stuff either. And I've read a lot of the similarly themed questions here on the forum but they've all been about stuff more technical than I'm concerned about.   Can somebody please just tell me in real layman's terms about the implications of these two choices? Thank you. Coordinating conjunction immediately followed by parenthetical — Is a comma needed or not? states:     If a dependent clause, or an introductory phrase requiring to be set off by a comma, precedes the second independent clause, no comma is needed after the conjunction.   Strunk's example illustrates the point:     The situation is perilous, but if we are prepared to act promptly, there is still one chance of escape.   However, I would be tempted to put a comma after the "but," like this:     The situation is perilous, but, if we are prepared to act promptly, there is still one chance of escape.   So, I know you're thinking, "Well, Strunk's Rules of Usage says that you're wrong. No comma."   But is Rules of Usage really the best source? I'd like to see this rule in a more contemporary and authoritative source, like the Chicago Manual of Style.  There are many instances —  — where the comma is included before a parenthetical comment that comes after a coordinating conjunction.  Any authoritative source on the issue? $\lfloor x\rfloor + \lfloor y\rfloor \leq \lfloor x+y\rfloor$ for every pair of numbers of $x$ and $y$ Give a convincing argument that $\lfloor x\rfloor + \lfloor y\rfloor \leq \lfloor x+y\rfloor$ for every pair of numbers $x$ and $y$. Could someone please explain how to prove this? I attempted to say that the largest values that could be added to $x$ and $y$ is $0.99$ and that doing so still made $\lfloor x\rfloor + \lfloor y\rfloor &lt; \lfloor x+y\rfloor$. However, my answer was not accepted. Make an Ubuntu bootable USB drive for a PC using Mac? select all rows with a minimum value I'm new to Linux. I got the "Unix And Linux System Administration Handbook" It speaks of several verisons of linux and unix, and the commands for viewing linux man pages and not specific to ubuntu.   How do I view the manpages? Where did object dimensions go in 2.8? Anyone seen this panel? Essential for precise modeling. How to remove illegal characters from path and filenames? Short brandable domain vs. long keyword domain I need a counsel about my websites' domain.  Let's say I have just bought two domains: xyz.com and xyzphotography.com.  As we can see, the first one is shorter but way less meaningful than the second one. The second one contains a photography keyword but it's longer.  I have only one website which is my photography portfolio. Can you advise me how to set those domains to make it all as SEO-friendly as possible? Which one should be the main one, does the rest should work on their own or have some kind of SEO-friendly redirect to the main domain? How to create and design hoops net and attach ot to a hoop? Is it possible to create an iron door which responds to levers on both sides This is a pretty well known quote from the Star Wars movies. But isn't it a bit paradoxical?   It in itself is an absolute, and it was said by a Jedi (Obi-Wan if I recall correctly?). If this holds true, then is he leaning towards the Sith himself? If it isn't true, then both Jedi and Sith can deal in absolutes and the statement is pointless.  Surely it should be phased along the lines of "Jedi's should avoid dealing in absolutes" or something similar? Variable doesn't get returned from AJAX function