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How to check if user account is locked or not in Linux

Posted 14 July 2023
By Iulian gheorghe
-1
208

Check account status in Linux with passwd command

To check if an account is locked in Linux, you can use the passwd command with the -S option. Here’s how you can do it:

Open a terminal or SSH into the Linux system as a user with sufficient privileges (such as the root user or a user with sudo access).
Run the following command, replacing <username> with the username of the account you want to check:

passwd -S <username>

For example, to check if the account “kent” is locked, you would run:

passwd -S kent

The output of the command will provide information about the account status. If the account is locked, you will see an “L” or “LK” in the second field of the output. If the account is unlocked, you will see “P” or “PS” in the second field.

“L” or “LK” indicates that the account is locked.
“P” or “PS” indicates that the account is unlocked.

Here’s an example of the output when an account is locked:

john LK 2021-06-01 0 99999 7 -1 (Password locked.)

And here’s an example of the output when an account is unlocked:

john PS 2021-06-01 0 99999 7 -1 (Password set, SHA512 crypt.)

Check account locked or not in Linux with /etc/shadow file

Apart from the methods mentioned earlier, there is another way to check if an account is locked in Linux by examining the /etc/shadow file. The /etc/shadow file stores the password information for user accounts.

The `/etc/shadow` file in Linux contains the hashed password information for the system’s users, among other things. It is the file where the user’s password (in hashed format), password expiry information, and account status are stored.

To check if a user’s account is locked, you can inspect the password field in the `/etc/shadow` file for that user.

Here is a typical entry in the `/etc/shadow` file:

username:$6$KBzX3L6T$VY5ddba27R4KDAY/:18599:0:99999:7:::

The entry is made up of several fields separated by colons:

1. Username
2. Password (hashed)
3. Last password change (days since UNIX epoch)
4. Minimum password age
5. Maximum password age
6. Password warning period
7. Password inactivity period
8. Account expiration date
9. Reserved field

The password field (2nd field) is where you can see if an account is locked. If the password field contains `!` or `*`, the account is locked.

You can use the `grep` command to quickly check a user’s entry. Replace `username` with the name of the user you want to check:

sudo grep "^username:" /etc/shadow

The `^` symbol ensures that lines starting with the username are matched (to avoid matching usernames that contain the target username as a substring).

Please note that you need to have superuser (root) privileges to read the `/etc/shadow` file. That’s why the `sudo` command is used.

Here’s an example of an entry in the `/etc/shadow` file for a **locked** account (for a user named `lockeduser`):

lockeduser:!$6$KBzX3L6T$VY5ddba27R4KDAY/:18599:0:99999:7:::

In this example, you’ll notice a `!` symbol right at the beginning of the password hash. This indicates that the account is locked, and the user won’t be able to log in using password authentication.

And here’s an example for an **unlocked** account (for a user named `unlockeduser`):

unlockeduser:$6$KBzX3L6T$VY5ddba27R4KDAY/:18599:0:99999:7:::

In this case, the password field begins with the hash algorithm ID (`$6$` stands for SHA-512), followed by the salt and the hashed password. There’s no `!` or `*` symbol at the beginning, indicating that this account is unlocked and the user should be able to log in with their password.

Please note that the actual hash and salt values in your `/etc/shadow` file will be different. The ones used in these examples are for illustrative purposes.

how to unlock account in Linux

If the account is locked, you can unlock it using the passwd command with the -u option. For example:

passwd -u <username>

Replace <username> with the actual username of the locked account.

Note: The specific command and options may vary slightly depending on the Linux distribution you are using.

You can also use usermod command with the -L switch to lock the given user account.

Run the usermod command with the -U switch to unlock the given user account.

# usermod --unlock howtouselinux

# usermod -U howtouselinux

[mai mult...]

How to fix ssh: connect to host port 22: Connection refused

Posted 14 July 2023
By Iulian gheorghe
-1
187

The syntax for the SSH command is as follows:

ssh [options] [user@]hostname [command]

Here is a brief explanation of each part of the syntax:

ssh – This is the command to initiate the SSH connection.
[options] – This is an optional parameter that allows you to specify additional options to configure the SSH connection. For example, you can use the -p option to specify a non-standard SSH port.
[user@]hostname – This is the remote host that you want to connect to. You can optionally specify a username to use for the SSH connection. If you omit the username, the default username for your current session will be used.
[command] – This is an optional parameter that allows you to specify a command to run on the remote host after the SSH connection is established. If you omit this parameter, you will be dropped into an interactive shell on the remote host.

Here is an example of how to use the SSH command to connect to a remote host:

ssh username@example.com

This will initiate an SSH connection to the host example.com using the username username.

If you have already set up SSH keys, you will be logged in without being prompted for a password. If not, you will be prompted to enter your password.

Verify SSH server status

Ensure that the SSH server is running and accessible on the host you are trying to connect to. Log in to the host using an alternative method like remote desktop or console access, and check the SSH server’s status with the following command:

systemctl status ssh

If the SSH server is not running, start it using the appropriate command for your system. For example:

systemctl start ssh

Confirm SSH server port

By default, SSH servers listen on port 22. However, it’s possible that the SSH server on the host you’re trying to connect to is configured to use a different port.

To check which port the SSH server is using, you can follow these steps:
Log in to the server where the SSH server is running. You can use an alternative method like remote desktop or console access if you cannot establish an SSH connection.
Once you’re logged in to the server, open a terminal or command prompt.
Run the following command to view the SSH server’s configuration file:

sudo nano /etc/ssh/sshd_config

This command opens the SSH server configuration file in the Nano text editor. Look for the line that specifies the port number. It typically looks like this:

Port 22

If the port number is set to the default value of 22, it means the SSH server is using the default port. If a different port number is specified, take note of that number.
After noting the port number, press Ctrl+X to exit the Nano editor. You will be prompted to save the changes made to the file. If you did not make any changes, simply press N to exit without saving.
Remember, if the SSH server is using a non-standard port, you will need to specify that port when connecting to the server using SSH. For example:

ssh -p <port_number> <username>@<host>

If you do not have access to the server’s configuration file, you can also try checking the SSH server’s status and listening ports by running the following command:

sudo netstat -tuln | grep ssh

This command will display the active TCP/UDP connections and listening ports on the server. Look for the line that includes “ssh” to find the port number being used by the SSH server.

Verify network connectivity

Verifying network connectivity is an important step when troubleshooting the “ssh: connect to host <host> port 22: Connection refused” error. It helps determine if there are any network-related issues that might be preventing your SSH client from reaching the SSH server.

The ping command is a common tool used to test network connectivity between two devices. When you execute the ping <host> command, your computer sends a small network packet to the specified host, and if the host is reachable and responsive, it sends a reply back.

If the ping command returns a response from the host, it indicates that the network connection is working fine. In this case, the “ssh: connect to host <host> port 22: Connection refused” error is likely due to a different issue, such as the SSH server not running or a firewall blocking the SSH connection.

However, if the ping command fails to receive a response or shows that the host is unreachable, it suggests a network connectivity problem.

This could be caused by various factors, such as network configuration issues, routing problems, network outages, or firewall restrictions. To resolve the issue, you may need to troubleshoot the network components, check network settings, contact your network administrator, or consult with an IT professional.

Firewall blocking the connection

When encountering the “ssh: connect to host <host> port 22: Connection refused” error, one possible cause is a firewall blocking the SSH connection.
Firewalls are security measures that monitor and control network traffic, and they can be set up at different points within a network, including the SSH server or any intermediate network devices.
Firewalls often enforce rules that determine which network connections are allowed or blocked.
Determine if the firewall is on the SSH server itself or if it is located on an intermediate network device, such as a router or a dedicated firewall appliance.
If the firewall is located on an intermediate network device, such as a router, you need to configure it to permit SSH traffic to reach the SSH server. Again, consult the documentation or seek assistance from the network administrator to adjust the firewall rules accordingly.

As a troubleshooting step, you can temporarily disable the firewall(s) to determine if they are indeed the cause of the connection issue. This should only be done for testing purposes and should not be a permanent solution. Always exercise caution when making changes to firewall configurations.

[mai mult...]

How to extend your Samsung Galaxy battery life

Posted 09 March 2023
By Iulian gheorghe
-1
486

1. Reduce display brightness level

High display brightness and long screen time-out setting will increase battery drain. One of the simplest way to prolong your device battery life is to reduce the screen brightness, and here’s how you can do it:

1) From the home screen > swipe down from the top to view the notification panel

2) Drag the brightness slider towards the left

3) At the same time, adjust the screen time-out setting > Tap the gear icon at the top > Select My Device tab > Select Display

4) Tap Screen timeout > Set your time-out preferences

Special Tip: Try setting your screen timeout to 30 seconds and display brightness to Auto.

2. Close, disable or uninstall unused Apps

Some apps may run background processes that deplete your battery. Once you’re ready to uninstall your unused apps, there are a few ways to go about it.

Fastest way to uninstall apps:

1) On your home screen > long-press on the app
2) Tap the Uninstall icon > Followed by OK

For more control over your apps:

1) Go to Settings > Apps.
2) Tap the overflow icon on the top right to sort apps by size or required permissions.
3) To uninstall, simply tap on the app name followed by the Uninstall icon.

Disable apps to increase battery life:

Unfortunately, some apps cannot be uninstalled on the certain Galaxy devices like Samsung Galaxy S9/S9+. However, you can disable the apps to increase battery life. To disable apps, simply follow either of the paths above and select Disable.

3. Turn off Always On Display (AOD) or set schedule

Always On Display or AOD uses AMOLED displays to show you certain information when your screen is “off”. It allows you to easily check basic information such as date and time without activating the display. Naturally, any activity that makes your screen turn on all the time will consume some power from your battery. You can choose to turn off AOD or set a time schedule for AOD to turn on/off.

To turn off AOD:

1) Go to Settings > Lock screen and security > Lock screen and Always On Display
2) Turn off AOD by tapping on the AOD slider (circle will move to the left)

4. Toggle off WiFi, Bluetooth and GPS when not in use

Switch off Wi-Fi, Bluetooth and GPS if you don’t need them, as each regular checks for a signal uses power. You can switch each of these off by pulling down the notification panel (drop down menu) and tapping the relevant icon.

5. Turn on Power saving mode

Power saving mode conserves battery power by limiting mobile device CPU performance, reducing screen brightness, turning off the touch key light and vibration feedback. This mode differs slightly between devices but generally it will close all unnecessary apps and screens so that you can substantially increase your battery time. You can turn on Power saving mode manually, or you can set your device to go into Power saving mode automatically.

Go to Settings > Device maintenance > Battery.

6. Download the latest device software

Check your latest device software by going to Settings > About phone.
Upgrade your software using either FOTA (‘Firmware Over The Air’, i.e. wirelessly) or via Samsung Kies.

7. Check your device Signal bars

Check the number of bars that you normally see on your handset while at home or work. Using the handset in areas with very low signal uses a lot of power and should be avoided where possible.

8. Check how often your device synchronises data

If like most people, you have a number of apps on your device such as email or social media, these apps will frequently sync, or check for new emails or updates. Frequently syncing can reduce your battery life. Check the sync settings on your apps or email, and ensure they only sync as often as you need them to.

9. Avoid fully discharging your battery

On much older types of batteries, the advice used to be to discharge them completely. However, completely discharging the battery on modern smartphones devices may reduce its life. It’s best not to let your battery go under 20%.