![]() If the problem exists because the permissions for /etc/sudoers are wrong, enter this: chmod 440 /etc/sudoers If the problem exists because the user account was removed from the admin group, enter the following: adduser username admin If someone has physical access to your computer and knows what he or she is doing, that person can easily and quickly gain full control over the machine and all it contains. This is an example of why security of a physical machine is important. You now have complete root access and read/write privileges on the machine. Enter the following: mount -o rw,remount / You are now at the command line, with full root access to the computer.īecause Ubuntu mounts file systems as read-only by default in recovery mode, you need to remount the root file system, /, as read/write so that you can fix the problem. When the boot process finishes, and have several options, select the menu entry for root: Drop to Root Shell Prompt. When the GRUB menu page appears, use the arrow keys on your keyboard to scroll to the entry that ends with (recovery mode) and press Enter to select it. Hold down the Shift key while the computer is booting. You can do this by booting into recovery mode, using the following steps: This is an obvious problem because if sudo is not working, the account does not have access to root. ![]() Take heed: It is better to spend a bit more time learning than it is to take a shortcut that causes bigger problems.įixing any of these problems requires the use of root powers. These problems generally result from users doing something they should not have done, such as changing the permissions on all files rather than taking the time to figure out a specific file that is causing problems due to permissions issues. When the /etc/sudoers file has been changed in a way that does not allow members of the sudo group to use root powers When the permissions for the /etc/sudoers file have been changed to anything other than 440 When the user is taken out of the sudo group but should not have been If both conditions are met, the user will be permitted to temporarily use root powers for specific commands that are issued at the command line by that user account by prefacing the command with the word sudo.Ī problem can occur for a specific user with sudo in several situations: In order for a user to use sudo, the user account must belong to the sudo group and must also be listed in the /etc/sudoers file. Either way, you can fix the problem by using the following knowledge and procedure. Sometimes, you might not even receive an error message, but the command issued simply does nothing. You usually can tell that a problem has occurred because an error message like this appears when a user tries to issue a command using sudo: sudo shutdown -h now Enter the root password, and you are then editing /etc/fstab, using the nano editor with line wrapping disabled (thanks to the -w). This extra step can also help you think before you leap into the command. For example, if you would like to edit your system’s file system table (a text file that describes local or remote storage devices, their type, and location), you can use sudo like this: sudo nano -w /etc/fstabĪfter you press Enter, you are prompted for a password that gives you access to root. ![]() In Ubuntu, you can use sudo to execute single commands as root and then immediately return to normal user status. Knowing how to run commands as the super user (root) without logging in as root can help avoid serious missteps when configuring your system. Logging in and using Linux as the root operator isn’t a good idea because it defeats the entire concept of file permissions. The only time you should run Linux as the super user is when you are configuring the file system, for example, or to repair or maintain the system. This alone is reason enough to take precautions when using root access. ![]() This command line not only deletes files and directories but also could wipe out file systems on other partitions and even remote computers. When you work in root, you can destroy a running system with a simple invocation of the rm command like this: sudo rm -rf / When logged in as root, you have total control over your system, which can be dangerous. You must have root permission to edit these files or to access or modify certain devices (such as hard drives). Super user permissions are required in part because of the restrictive file permissions assigned to important system configuration files. The root, or super user, account is a special account and user on UNIX and Linux systems. ![]()
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