I'm a beginner to Ubuntu. Can anyone tell me how to edit a configuration file?
This is on Ubuntu 18.04 LTS. Thanks in advance.
Configuration files are usually owned by
root. For example:
$ ll /etc/default/grub -rw-r--r-- 1 root root 6801 Jul 18 13:26 /etc/default/grub ^^ ^ ^ || | +-- Users can only read || +----- Members of the group can only read |+------- The owner can write +-------- The owner can read
In order for a user (yourself) to edit
/etc/grub/default you need to use
sudo powers. So instead of using:
You must use:
sudo -H gedit /etc/default/grub
At which point you will be prompted for your password.
Note: Related question today: Grub file can't be saved after modification
System-wide configuration files, which are often in
/etc, are owned by root and you need to elevate your privileges to edit them. It's common to run a text editor as root with
sudo, and other answers here show how. But just because only root can make changes the files does not mean you have to run your text editor as root. You can instead use
sudoedit, which is documented in the same manpage as
For example, to edit
The way this works is that
sudofrom the terminal you're in (like
sudodoes), an prompts you for your password if you haven't.
sudo. If so, it gives you an error message and quits. (In this situation, you should just edit the file normally as DK Bose says, assuming it makes sense to do so.)
sudoedit works with your choice of text editor. To edit with
VISUAL=nano sudoedit /etc/hosts
It even works with GUI editors like Gedit:
VISUAL=gedit sudoedit /etc/hosts
Furthermore, because the editor is run as you, it uses your configuration, so if you've customized the behavior of your editor, those customizations are used. Other ways of attempting this tend not to work very well.
You can set the
VISUAL environment variable persistently for your user to make
sudoedit, and various other commands that need to pick an editor, use your preferred editor. If you want to set an editor just for
visudo) but not other programs, set
SUDO_EDITOR instead of
Because the logic of checking if two files are the same and copying one onto another is simpler than the full logic of a text editor--and especially simpler than the full operation of a graphical program like Gedit--running
sudoedit might be considered more secure in the specific sense that it is associated with a smaller attack surface. Running less stuff as root is good. But the main reason to use
sudoedit is convenience.
sudoedit is so useful and versatile, its benefits are sometimes overstated. It's a good tool, but you don't have to use it, and using it instead of other methods doesn't affect security in any decisive way. If you change system-wide configuration files in a way that breaks things, they will still break! That seems obvious when stated that way, but sometimes people try to give users the right to edit files owned by root with
sudoedit while still trying to restrain those users in some way through technical measures. This is not usually practical.
There are also configuration files in your home folder and its subfolders such as the .config folder. The preceding "." signifies the folder (or file) is hidden normally. Some config files may also be directly in your home folder. If you're using a file manager, Control+H will hide/reveal such files/folders.
Such files can be edited by a plain text editor with convenient GUIs (graphical user interfaces) similar to notepad in Windows. Editing such files should not require the use of sudo since you are the owner of these files. Indeed using sudo on files in your home folder is rarely, if ever, needed.
Some examples of plain text editors, most of them offering syntax highlighting, bracket matching, etc:
You could also use LibreOffice Writer but make sure you save your file as plain text and not in LibreOffice Writer's default Open Document Format.
Mostly though, you needn't edit config files directly. (That's why these files are mostly in hidden folders.) The preferred way is to use the GUI of whichever application your using. That way, you'll avoid making any "syntax" errors.
As mentioned by WinEunuuchs2Unix, most of the configuration files are owned by root so typing "sudo" before the editor of your choice is necessary. I use "vim" to edit files so from the command line I type
sudo vim (filename).
or if you use nano which comes with Ubuntu by default
sudo nano (filename)
There are many editors you can choose from; vim, emacs, gedit, nano, and many more.
Also, as I mentioned in my comment above it is recommended to run
sudo visudo by itself if editing the sudoers file and also
crontab -e when adding cron entries. Both of these commands will essentially open up the vim editor for editing files by default so I recommend getting familiar with vim but also exploring the other editors out there. It is very important to read the comments or notes at the top of configuration files to see if the system recommends against editing the files directly.