If you are inside a Vagrant box and want to SSH to the host machine, you will need to get the default gateway. Or, maybe you just need the default gateway for a completely different reason. Either way, the following command should do it.
netstat -rn | grep "^0.0.0.0 " | cut -d " " -f10
This is really useful if you don’t have ifconfig installed.
These days cPanel comes with Git. However, it is not available as a command by default but is instead hidden away in cPanel’s usual obscure location.
However, you can make it accessible using a symlink.
ln -s /usr/local/cpanel/3rdparty/bin/git /usr/local/bin/git
That will allow you to use the git command as normal. The version you get is likely to behind the current version of Git though.
If you’re trying to create an SSH tunnel, you may find that running the command just logs you into the remote server.
ssh -L 27017:somehost:27017 user@examplehost.net
To solve this, you need to use the -N flag.
ssh -L 27017:somehost:27017 -N user@examplehost.net
This will then just set up the forwarding, and not run the command.
Lets say you are trying to create an SSH tunnel.
ssh -L 27017:somehost:27017 you@examplehost.net
You may get the following error message.
ssh: Error resolving hostname \342\200\223L: nodename nor servname provided, or not known
This is caused by using the wrong kind of minus symbol. If you have copied and pasted the command from somewhere, this is probably the case. This is easy to fix – simply paste the command into your terminal, then go through it, remove the existing minus symbol and put a new – in.
Sometimes, you might find that when you try and SSH into another server, it seems to hang, but then after around 30 seconds or so, will suddenly start working again. You can diagnose where it is stopping by using verbose mode.
ssh -vv user@example-server
If you find it is to do with GSS API, you can disable this in your SSH configuration.
cd ~/.ssh/ vim config
Add the following to it.
GSSAPIAuthentication no
This should then speed the login up.
If you find your screen resolution suddenly drops too 800×600 on Ubuntu 12.04, the following set of commands may help you resolve it. First, stop the graphical environment.
sudo service lightdm stop
Now remove all the Nvidia packages and reboot the system.
sudo apt-get purge nvidia* sudo reboot
This will reset you to the default video driver. You now need to reinstall the Nvidia driver, which you can do by going to System settings > Additional Drivers and selecting the top option with the following name.
NVIDIA binary Xorg driver, kernal module and VPDAU library
Select this and click activate. Now reboot your system again and the Nvidia drivers will be re-installed and hopefully working again.
If you’ve tried to switch to a different Nvidia graphics driver on Ubuntu and suddenly found that X / Gnome will no longer load and all you have is a command line, you can fix it by switching back to the original driver.
jockey-text -l jockey-text -e xorg:nvidia_current
These commands will show you a list of drivers available, and then activate the standard Nvidia driver.
To install Imagick, you would normally do this via PECL.
sudo pecl install imagick
However, when trying this on Ubuntu 12.04 LTS, you may get an error similar to the following.
checking ImageMagick MagickWand API configuration program... configure: error: not found. Please provide a path to MagickWand-config or Wand-config program
You can resolve this by installing a few extra packages.
sudo apt-get install libmagickwand-dev libmagickcore-dev
Now try re-running the original command and it should be successful.
If you want a service to start automatically when Gentoo boots up, you need to tell Gentoo to start it. Gentoo looks at /etc/runlevels/boot to see what it needs to run, so all you need to do is add a symlink in here to your init.d script. In this example, I’ll use exim.
cd /etc/runlevels/boot ln -s /etc/init.d/exim exim
Next time Gentoo boots, it will see exim in the boot directory and run the script. This isn’t just limited to boot either – /etc/runlevels also has directories for shutdown and system initialisation.
If you’re trying to install ThoughtWorks’ Go Server on CentOS (or indeed any Linux variety), you might run into a problem where it says you need JDK installed. Indeed, even if you have OpenJDK installed it may continue to complain.
This is because they have not officially approved OpenJDK yet, so your two options are to a) installed the actual JDK or b) to install OpenJDK to at least the version required (1.6 at time of writing) and then force the installer to ignore dependences. This can be done using the following command.
rpm -i --nodeps go-server.rpm
Providing you already have OpenJDK installed, this should work fine.