Problem
If by accident you make a mistake in your sudoers file then you won’t be able to run sudo command after saving the file.
Solution
Following the answer here, you can simply run the command pkexec visudo, supply your password and provided you already had sudo permissions, fix the sudoers file, make sure that you save it using the Q when prompted, and you should be able to use sudo commands again.
Problem
You want to run a service/script on a server that you have logged in with ssh, but you want to leave it running even after you have terminated the ssh session.
Solution
Use the nohup command so do the following in your ssh session:
nohup /service/i_want_to_run &
Problem
You want to search in a directory or some files for a specific string and you also want to know the number in the file that the text is found.
Solution
Use grep with the -n for the line number and the -r for directory search as in the following:
grep -n -r 'search_item' /path/to/folder/
Problem
When trying to use the new Capistrano 3.x to set up your rails project in a dreamhost account, you get the following error complaining that the git-ssh.sh script copied to your account by capistrano cannot be executed as the permission is denied:
fatal: cannot exec '/tmp/example.com/git-ssh.sh': Permission denied
Solution
It seems that Dreamhost, and quite possibly other hosting providers are not allowing executables from the /tmp directory, which is where Capistrano places the git-ssh.sh script. So in order to be able to execute the script you can change the directory where the script is copied in the first place and put it in your home directory. You can do that by adding the following to the config/deploy.rb file:
set :tmp_dir, "/home/dh_user_name/tmp"
Problem
In your rails project very often, after creating a new migration, you have to run the migration in the development database and then in the test database.
Solution
A neat way to combine both these steps as one, taken from the book Rails 4 in Action, is to create an alias in your ~/.bashrc configuration file with the following, so that you only have to run migrate after each migration that would apply the migration in both development and test databases:
alias migrate='bin/rake db:migrate && bin/rake db:test:prepare'
Problem
You have forgotten your web-gui credentials to login into your dd-wrt router but you have still telnet access to it.
Solution
Login with telnet to your router and then run the following two commands to reset the web interface:
nvram set http_passwd= nvram commit
and then go to your Web interface to set a new one.
* Based on this post
Problem
After a new rvm installation in an (k)ubuntu system you get the following error from rvm when trying to switch between rubies:
You need to change your terminal emulator preferences to allow login shell. Sometimes it is required to use `/bin/bash --login` as the command. Please visit https://rvm.io/integration/gnome-terminal/ for a example.
Solution
As the message suggests you can change the setting in your terminal which is fine if you are using the gnome-terminal by going to the link provided:
Please visit https://rvm.io/integration/gnome-terminal/ for a example.
but if you are using Konsole in KDE you need to go to a different link that explains the change in the settings:
Please visit http://rvm.io/integration/konsole/ for a example.
Problem
You would like to integrate your BitBucket git repository with your Pivotal Tracker issue tracker.
Solution
After creating your bitbucket git repository and pivotal tracker project, do the following.
You can now use commits that have a square bracker [#111111] with the pivotal issue ticket and update pivotal when making a commit
Problem
You would like to automatically delete old releases from your rails app server using a puppet crontab resource.
Solution
Add the following to your modules/crontab/manifests/init.pp file and modify some of the values to what you need:
# use // to suppress warning: Warning: Unrecognised escape sequence '\;'
cron { remove_old_releases:
command => "test $(find /var/www/your/path/to/ror/app/ -maxdepth 1 -type d | wc -l) -gt 10 && find /var/www/your/path/to/ror/app/ -maxdepth 1 -type d -mtime +14 -exec rm -rf '{}' \\;",
user => ubuntu,
hour => 0,
minute => 15
}
You should need to change the following:
/var/www/your/path/to/ror/app/ to your application’s release path
-gt 10 this is the number of minimum old releases you want to keep
-mtime +14 releases older than 14 days are deleted
UPDATE
There is chance that when you do not calculate the frequency of the releases right the above script can potentially delete all of your releases, so you end up with no releases 🙁
A better solution to keep the -n number of releases (based on the solution from here:
find /var/www/your/path/to/ror/app/* -type d -printf '%T@ %p\n' | sort -nr | tail -n+6 | cut -f 2- -d " " | xargs -i rm -rf {}
and the explanation of each step:
So the puppet script should be as follows (including the escape characters \ for the % and the additional \):
# use // to suppress warning: Warning: Unrecognised escape sequence '\;'
cron { remove_old_releases:
command => "find /var/www/your/path/to/ror/app/* -maxdepth 0 -type d -printf '\\%T@ \\%p\\n' | sort -nr | tail -n+6 | cut -f 2- -d ' ' | xargs -i rm -rf '{}' \\;",
user => ubuntu,
hour => 0,
minute => 15
}
Problem
You would like to set up your vim editor to use 2 spaces for the tab character.
Solution
Add the following to your ~/.vimrc file:
set ts=2