If you are using CentOS 7 and Gnome, you can change the password with xwindoes Applications- System Tools - Settings - Users user who you want to change the password, and then input the new password Regards, Sam. Sep 04, 2013 The same algorithm is run on the password that is given during authentication and this value is compared to the value in this file. Note that this file, unlike the '/etc/passwd' file, is not readable by unprivileged users. The root user has read and write permissions, and the 'shadow' group. Sep 05, 2019 However, if you had set up lock period for 24 hours you might need to unlock the user’s account manually. This tutorial will help you to manually lock and unlock users account in Linux. This can be done using the following two Linux Commands in three ways. Passwd: This is used to update user’s authentication tokens. This is achieved by calling the Linux-PAM and Libuser API.
GRand Unified Bootloader (GRUB) is likely the first thing you see when you boot a virtual machine (VM). Because it's displayed before the operating system has started, GRUB isn't accessible via SSH. In GRUB, you can modify your boot configuration to boot into single-user mode, among other things.
Single-user mode is a minimal environment with minimal functionality. It can be useful for investigating boot issues, file system issues, or network issues. Fewer services can run in the background and, depending on the runlevel, a file system might not even be automatically mounted.
Single-user mode is also useful in situations where your VM might be configured to accept only SSH keys for sign-in. In this case, you might be able to use single-user mode to create an account with password authentication.
Note
The Serial Console service allows only users with contributor level or higher permissions to access the serial console of a VM.
To enter single-user mode, enter GRUB when your VM is booting, and modify the boot configuration in GRUB. See detailed instructions for entering GRUB in the next section. In general, if your VM has been configured to display GRUB, you can use the restart button within your VM's serial console to restart the VM and display GRUB.
General GRUB access
To access GRUB, reboot your VM while the Serial Console pane is open. Some distributions require keyboard input to show GRUB, and others automatically show GRUB for a few seconds to allow user keyboard input to cancel the timeout.
To be able to access single-user mode, you want to ensure that GRUB is enabled on your VM. Depending on your distribution, some setup work might be necessary to ensure that GRUB is enabled. For distribution-specific information, see the next section and our Support for Linux on Azure page.
Restart your VM to access GRUB in Serial Console
You can restart your VM within Serial Console by hovering over the Restart button and then selecting Restart VM. A notification about the restart is displayed at the bottom of the pane.
You can also restart your VM by running a SysRq 'b' command if SysRq is enabled. To learn what to expect from GRUB when you reboot, see the distribution-specific instructions in the next sections.
General single-user mode access
You might need manual access to single-user mode when you haven't configured an account with password authentication. Modify the GRUB configuration to manually enter single-user mode. After you've done this, see the 'Use single-user mode to reset or add a password' section for further instructions.
If the VM is unable to boot, distributions often automatically drop you into single-user mode or emergency mode. Other distributions, however, require additional setup, such as setting up a root password, before they can drop you into single-user or emergency mode automatically.
Use single-user mode to reset or add a password
After you're in single-user mode, add a new user with sudo privileges by doing the following:
Access for Red Hat Enterprise Linux (RHEL)
If RHEL can't boot normally, it drops you into single-user mode automatically. However, if you haven't set up root access for single-user mode, you don't have a root password and can't sign in. There is a workaround (see the 'Manually enter single-user mode in RHEL' section), but we suggest that you set up root access initially.
GRUB access in RHEL
RHEL comes with GRUB enabled out of the box. To enter GRUB, reboot your VM by running
sudo reboot , and then press any key. The GRUB pane should be displayed. If it isn't, ensure that the following lines are present in your GRUB file (/etc/default/grub ):
For RHEL 8
For RHEL 7
Note
Red Hat also provides documentation for booting into Rescue Mode, Emergency Mode, or Debug Mode, and for resetting the root password. For instructions, see Terminal menu editing during boot.
Set up root access for single-user mode in RHEL
The root user is disabled by default. Single-user mode in RHEL requires the root user to be enabled. If you need to enable single-user mode, use the following instructions:
Now, if the system boots into single-user mode, you can sign in with the root password.
Alternatively, for RHEL 7.4+ or 6.9+, to enable single-user mode in the GRUB prompts, see Booting into single-user mode.
Manually enter single-user mode in RHEL
If you've set up GRUB and root access by using the preceding instructions, you can enter single-user mode by doing the following:
Enter single-user mode without root account enabled in RHEL
If you didn't enable the root user by following the earlier instructions, you can still reset your root password by doing the following:
Note
If you're using SELinux, when you reset the root password, be sure to follow the additional steps that are described in the Red Hat documentation.
Note
Running through the preceding instructions drops you into the emergency shell so that you can also perform tasks such as editing
fstab . However, we ordinarily suggest that you reset your root password and use it to enter single-user mode.
Access for CentOS
Much like Red Hat Enterprise Linux, single-user mode in CentOS requires GRUB and the root user to be enabled.
GRUB access in CentOS
CentOS comes with GRUB enabled out of the box. To enter GRUB, reboot your VM by entering
sudo reboot , and then press any key. This action displays the GRUB pane.
Single-user mode in CentOS
To enable single-user mode in CentOS, follow the earlier instructions for RHEL.
Access for Ubuntu
Ubuntu images don't require a root password. If the system boots into single-user mode, you can use it without additional credentials.
GRUB access in Ubuntu
To access GRUB, press and hold Esc while the VM is booting.
By default, Ubuntu images might not automatically display the GRUB pane. You can change the setting by doing the following:
Single-user mode in Ubuntu
If Ubuntu can't boot normally, it drops you into single-user mode automatically. To enter single-user mode manually, do the following:
Use GRUB to invoke bash in Ubuntu
After you've tried the preceding instructions, there might be a situation (such as a forgotten root password) where you're still unable to access single-user mode in your Ubuntu VM. You can also tell the kernel to run
/bin/bash as init, rather than the system init. This action gives you a bash shell and allows for system maintenance. Use the following instructions:
Access for CoreOS
Single-user mode in CoreOS requires GRUB to be enabled.
GRUB access in CoreOS
To access GRUB, press any key while your VM is booting.
Manually Add Password For Users In Centos DownloadSingle-user mode in CoreOS
If CoreOS can't boot normally, it drops you into single-user mode automatically. To enter single-user mode manually, do the following:
Access for SUSE SLES
Newer images of SLES 12 SP3+ allow access via the serial console if the system boots into emergency mode.
GRUB access in SUSE SLES
GRUB access in SLES requires a bootloader configuration via YaST. To create the configuration, do the following:
Single-user mode in SUSE SLES
If SLES can't boot normally, you're automatically dropped into the emergency shell. To enter the emergency shell manually, do the following:
Access for Oracle Linux
Much like Red Hat Enterprise Linux, single-user mode in Oracle Linux requires GRUB and the root user to be enabled.
Manually Add Password For Users In Centos VersionGRUB access in Oracle Linux
Oracle Linux comes with GRUB enabled out of the box. To enter GRUB, reboot your VM by running
sudo reboot , and then press Esc. This action displays the GRUB pane. If the GRUB pane isn't displayed, ensure that the value of the GRUB_TERMINAL line contains serial console (that is, GRUB_TERMINAL='serial console' ). Rebuild GRUB with grub2-mkconfig -o /boot/grub/grub.cfg .
Single-user mode in Oracle Linux
To enable single-user mode in Oracle Linux, follow the earlier instructions for RHEL.
Centos Reset User PasswordNext steps
To learn more about Serial Console, see:
Related
How to Add and Delete Users on Ubuntu 18.04 Tutorial
Centos Add User Account
How To Set Filesystem Quotas on Debian 10 Tutorial
Introduction
When you first start using a fresh Linux server, adding and removing users is one of the most basic tasks that you should know how to do. When you create a new server, you are only given the
root account by default. While this gives you a lot of power and flexibility, it is also dangerous to regularly use an account with so much power; for example, a root user is more vulnerable to security exploits, since any commands run under that account can affect the server’s entire filesystem.
It is almost always a better idea to add an additional, unprivileged user to do common tasks. You should also create additional accounts for any other users that need access to your server. Each user should have an additional account so that their activities can be monitored and managed. You can still acquire administrative privileges, when needed, through a mechanism called
sudo . In this guide, we will cover how to create user accounts, assign sudo privileges, and delete users on a CentOS 7 server.
Adding Users
If you are signed in as the
root user, you can create a new user at any time by typing:
If you are signed in as a non-root user who has been given
sudo privileges, as demonstrated in the next section of this tutorial, you can add a new user by typing:
Next, you’ll need to give your user a password so that they can log in. To do so, use the
passwd command:
Note: Remember to add
sudo ahead of the command if you are signed in as a non-root user with sudo privileges.
You will be prompted to type in the password twice to confirm it. Now your new user is set up and ready for use! You can now log in as that user, using the password that you set up.
Granting Sudo Privileges to a User
If your new user should have the ability to execute commands with
root (administrative) privileges, you will need to give the new user access to sudo .
We can do this by adding the user to the
wheel group (which gives sudo access to all of its members by default) through the gpasswd command. This is the safest and easiest way to manage sudo user rights.
If you are currently signed in as the
root user, type:
If you are signed in using a non-root user with
sudo privileges, type this instead:
Now your new user is able to execute commands with administrative privileges. To do so, simply type
sudo ahead of the command that you want to execute as an administrator:
You will be prompted to enter the password of the regular user account that you are signed in as. Once the correct password has been submitted, the command you entered will be executed with
root privileges.
Managing Users with Sudo Privileges
While you can add and remove users from a group (such as
wheel ) with gpasswd , the command doesn’t have a way to show which users are members of a group. In order to see which users are part of the wheel group (and thus have sudo privileges by default), you can use the lid function. lid is normally used to show which groups a user belongs to, but with the -g flag, you can reverse it and show which users belong in a group:
Centos Add Group To User
The output will show you the usernames and UIDs that are associated with the group. This is a good way of confirming that your previous commands were successful, and that the user has the privileges that they need.
Deleting Users
If you have a user account that you no longer need, it’s best to delete the old account. You have a couple of methods to do so, though the choice of which method to use depends on your own situation.
If you want to delete the user without deleting any of their files, type this command as
root :
If you want to delete the user’s home directory along with the user account itself, type this command as
root :
Note: Remember to add
sudo ahead of the command if you are signed in as a non-root user with sudo privileges.
With either command, the user will automatically be removed from any groups that they were added to, including the
wheel group if they were given sudo privileges. If you later add another user with the same name, they will have to be added to the wheel group again to gain sudo access.
Conclusion
You should now have a good grasp on how to add and remove users from your CentOS 7 server. Effective user management will allow you to separate users and give them only the access that is needed for them to do their job. You can now move on to configuring your CentOS 7 server for whatever software you need, such as a LAMP or LEMP web stack.
For more information about how to configure
sudo , check out our guide on how to edit the sudoers file.
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