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178

Ports are a concept of UDP and TCP. Ping messages are technically referred to as ICMP Echo Request and ICMP Echo Reply which are part of ICMP. ICMP, TCP, and UDP are "siblings"; they are not based on each other, but are three separate protocols that run on top of IP. Therefore you can not ping a port. What you can do, is use a port scanner like nmap. nmap ...


60

There's one more thing you need to know of: GNU. GNU stands for "GNU's Not Unix", and it is an attempt to create a free, independent version of Unix, developed by the Free Software Foundation. They got very far, they made a C compiler, a C library, a linker, editors, shells, all the commands you'd expect in a typical Unix shell, lots of stuff. But the ...


45

I use Telnet, since its built into lots of platforms with no additional downloads. Just use the telnet command to connect to the port you want to test. If you get the message below, or a message from the service itself, then the port is alive. Minty16 ~ $ telnet localhost 139 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. If you ...


38

Unix is an Operating System developed starting in 1969. It was originally designed to be a developer station rather than application platform, but, as development progressed and different vendors got involved, Unix was added to. Unix was initially written in assembly, but later developed into C. In relation to the others, the Linux kernel is Unix-like. ...


33

The easiest way to determine if 2 discs are the same is to run a hash of both of them: sudo md5sum /dev/cdrom If the hashes match, the disks are exactly the same. However this will not tell you what is different about them. Even if a single bit is different you would get a totally different hash. You can check the partition table of a disc with fdisk: ...


29

You probably only need a small amount of swap. When you have sufficient RAM for your computer's typical working set, which I'm pretty sure you do, you only need swap for two things: You need swap to get information that will likely never be accessed out of RAM to free up more space for disk cache. Many applications run on system startup and will never be ...


29

Stole this from AskUbuntu, from someone who stole it off of Hacker News. Worked on two old servers for me mkdir src cd src wget http://ftp.gnu.org/gnu/bash/bash-4.3.tar.gz #download all patches for i in $(seq -f "%03g" 1 28); do wget http://ftp.gnu.org/gnu/bash/bash-4.3-patches/bash43-$i; done tar zxvf bash-4.3.tar.gz cd bash-4.3 #apply all patches for i ...


24

RedHat recommends 4 GB on a machine with 64 GB. However, sizing swap is more of an art than a science. It depends on what the machine is being used for, how much disk space and memory you have, and other factors. Remember, you can always add more swap later. Using the 2X physical memory rule is outdated with the amount of memory systems have ...


23

In short: apt-get install does everything that is needed that your system can successfully execute the new installed software application. Longer version: Preliminaries: From the manpage: All packages required by the package(s) specified for installation will also be retrieved and installed. Those packages are stored on a repository in the ...


22

For Unity (shipped by default since the Ubuntu12), Gnome, LXDE, Cinnamon and MATE, the Ctrl+Alt+T keyboard shortcut will work if you are already logged in. If you are using Xfce (Xubuntu), however, it would be Super+T. (Note that Super is the Windows key) And as far as I am aware, in KDE, while it is also Ctrl+Alt+T, for some reason, there are issues with ...


21

Just hit Ctrl+Alt+F1 to switch to another tty. That's probably easiest.


20

You can use netcat to connect to a specific port to see if you get a connection. The -v flag will increase the verbosity to show whether the port is open or closed. The -z flag will cause netcat to quit once it has a connection. You can then use the exit codes through $? to see whether or not the connection was established or not. $ nc -zv localhost 22 ...


15

"Unix" was originally the name of an operating system for the PDP-11, developed at Bell Labs in the 1970s. Its design was immensely influential, and it was copied and reimplemented dozens of times. Nowadays, "Unix" is an umbrella term for an entire family of operating systems, some but not all of which are directly descended from that original OS; anything ...


14

Yes, use HPing to do that: $ sudo hping -S -p 80 google.com HPING google.com (p5p1 77.237.27.37): S set, 40 headers + 0 data bytes len=46 ip=77.237.27.37 ttl=58 id=25706 sport=80 flags=SA seq=0 win=29200 rtt=7.5 ms len=46 ip=77.237.27.37 ttl=58 id=25707 sport=80 flags=SA seq=1 win=29200 rtt=7.4 ms len=46 ip=77.237.27.37 ttl=58 id=25708 sport=80 flags=SA ...


13

Linux MD RAID info is most often written to the RAID superblock on each device, making it intrinsic to the array. This is the reason, why an array created by one installation can easily be found and started by another installation. There is the possibility of a non-superblock array, that must be assembled by using outside knowledge, but this is rather a ...


13

Yes, you can use visudo to edit those files. All that you have to do is specify the name of the file that you want to edit with the -f option. For example: visudo -f /etc/sudoers.d/somefilename Or, if needed: sudo visudo -f /etc/sudoers.d/somefilename Documentation From man visudo: -f sudoers Specify and alternate sudoers file location. ...


11

On Linux, you need enough swap so that the total virtual memory available (RAM + SWAP) is enough for all the processes you want to run at once and their maximum virtual footprint. If you have less swap than this, or no swap at all, then the following situation happens: the system runs out of memory trying to allocate a page. But, this is still a soft ...


10

When using VirtualBox the default resolutions are limited to just a few common resolutions. In order to enable the native resolution of your monitor you'll need to properly install the Guest Additons. Here's how you do this within Linux: Mount the Guest Additions by selecting Devices --> Insert Guest Additions CD image... run the ...


10

Ubuntu has started if you are able to do commands, it is just the gui you are missing. Now you just need to delete things with the rm command. Please be careful, and make sure you understand what you are doing. Perhaps you can delete some old logs? In the /var/log folder there are lots of logs. Anything ending in a number such as .1, or a number with a ...


10

The other answers here seem to assume the use of VMware Workstation, but since the OP has not yet clarified I will assume VMware Player. VMware Player does not have a snapshot feature, the idea being to entice you to purchase VMware Workstation. You can get around this by making a copy of your virtual machine using copy & paste, or by creating a .zip ...


9

I would personally try to boot from a live CD and try mounting /dev/sda7 that way. Once you can get it mounted, you should then go through and see what large files you can delete to free up space. I hope this helps!


9

pkill python Short and sweet, man pkill for details.


8

There are two ways to do this: Apt-get specific: $man apt-get [...] -y, --yes, --assume-yes Automatic yes to prompts; assume "yes" as answer to all prompts and run non-interactively. If an undesirable situation, such as changing a held package, trying to install a unauthenticated package or removing an essential package occurs ...


8

In Ubuntu 14 work for me Ctrl + Super + Up to maximize. Ctrl + Super + Down to minimize. Super aka Windows Key


8

Commands entered with a leading space are typically not stored in bash's history. This is a feature: if you want bash not to put a command in history, such as a dangerous command like rm -rf ..., place a space in front of it. Also, duplicate commands may be ignored. This behavior is configurable with the HISTCONTROL variable. From man bash: ...


7

Use Control+Shift+C to copy, and use Control+Shift+V to paste. References http://howtoubuntu.org/how-to-cut-copy-and-paste-in-the-terminal-in-ubuntu http://stackoverflow.com/questions/761807/copy-and-paste-from-terminal-with-keyboard-in-linux-ubuntu


7

Changes made to files in /etc/sudoers.d remain in place if you upgrade the system. This can prevent user lockouts when the system is upgraded. Ubuntu tend to like this behavior. Other distributions are using this layout as well. It has been my experience that the rules on files in this directory are looser than for /etc/sudoers. This has included: ...


7

why do we have /etc/sudoers.d? Because it's easier for automated tools (such as Chef or Puppet) to drop individual files into this directory, rather than making changes to /etc/sudoers, which might be fragile. The files in /etc/sudoers.d are (in effect) concatenated. You'll see several other instances of this pattern in /etc, such as /etc/cron.d and ...


7

Enter the following commands in a terminal to enable 1920x1080 resolution: xrandr --newmode "1920x1080" 173.00 1920 2048 2248 2576 1080 1083 1088 1120 -hsync +vsync xrandr --addmode Virtual1 1920x1080 xrandr --output Virtual1 --mode 1920x1080 This will set your display resolution to 1920x1080 and also enable several other 16:9 aspect ratio resolutions ...


7

Just comparing the folders and files misses other things about the disc. If you create an .ISO image file from each disc and byte compare them you'd have a better idea of the discs are really the same or not.



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