Tag: ubuntu

Fix: Unable to Use Package Manager Due to Exclusive Lock Error

Learn how to resolve the ‘exclusive lock’ error when using a package manager like apt on Linux systems. Step-by-step fixes for Ubuntu and Debian-based distros.

After start, Synaptic Manager in Ubuntu sometimes gives error

Unable to get exclusive lock. This usually means that another package management application(like apt-get or aptitude) is already running. Please close that application first.

In this post, we will learn about the causes and solutions for this error.

There are multiple causes for this error. As the message says, it means that package manager is already running.

After Boot

Cause

By default, Ubuntu runs a check after reboot automatically — not immediately, but some time within. So, during this time if you try to run the update command, you will get this error.

Solution

For Ubuntu automatic system checks, you have to wait for it to complete and then run your update command.

You can check, if any system check is running or not using the following command,

ps aux | grep dpkg | grep -v grep

If it shows any text then it means system is still updating, just wait for it to completed.

Software Updater is Running

Cause

Sometimes after boot, system software updater popup comes with many system updates. You can cancel this update and it will close. But, if you accept the updates, it will start updating the system.

If this updater is running and you try to run the update command, you will get same error as above.

Solution

Generally, it is not advised to pause the updater. Once an update has started, allow it to run its course. So, wait for some time till it completes and then run your update command.

Otherwise, you can pause the updater to run update command from terminal and restart the updater later after your update command completes.

Fix: phpMyAdmin Gives 404 Error in Localhost

Troubleshooting guide to fix the 404 error when accessing phpMyAdmin on localhost. Learn common causes and step-by-step solutions for Apache and Nginx servers.

To run phpmyadmin without getting 404 error, configure apache.conf for phpmyadmin.

gksu gedit /etc/apache2/apache2.conf

Then add the following line to the end of the file.

Include /etc/phpmyadmin/apache.conf

And restart apache

/etc/init.d/apache2 restart

Please read this section in Ubuntu wiki describes the 404 error problem for phpmyadmin.

How to Execute a JAR File from the Terminal on Ubuntu?

Learn how to run JAR files directly from the terminal on ubuntu. Includes syntax examples, troubleshooting tips, and Java runtime requirements.

To execute .jar file, java command should be used as below:

java -jar {path_of_the_file}/{file_name}.jar

And to execute above command, Java package must be installed on Ubuntu PC. To check if java package is already installed, execute below command in a terminal:

java -version

It should display current version of Java package installed.

If it displays “The program java can be found in the following packages”, It means Java hasn’t been installed yet. Execute below command in a terminal to install java package,

sudo apt-get install default-jre

This will install the Java Runtime Environment (JRE) only not Java Development Kit (JDK). If Java Development Kit (JDK) is needed, which is usually needed to compile Java applications, execute the following command in terminal:

sudo apt-get install default-jdk

That is everything to install Java. Now run first command to execute .jar file.

How to Reset a Forgotten phpMyAdmin Password

Forgot your phpMyAdmin password? Follow this simple guide to reset your MySQL root or user password and regain access to phpMyAdmin on localhost or server.

Forgetting your phpMyAdmin password can be frustrating, especially when you’re in the middle of working on a critical project. Fortunately, resetting the password is a straightforward process. This guide walks you through the steps needed to reset your phpMyAdmin (MySQL/MariaDB) root password on a local or remote server.

Step-by-Step Guide to Reset phpMyAdmin Root Password

Step 1: Stop the MySQL Service

Before making any changes, stop the MySQL or MariaDB service.

sudo systemctl stop mysql

Step 2: Start MySQL in Safe Mode

Run MySQL in safe mode without password authentication.

sudo mysqld_safe --skip-grant-tables &

This allows you to log in without needing a password.

Step 3: Log in to MySQL

Now log into MySQL as the root user:

mysql -u root

You’ll be taken directly to the MySQL shell.

Step 4: Change the Root Password

Run the following commands to change the root password.

For MySQL 5.7+ or MariaDB 10.1+:

FLUSH PRIVILEGES;
ALTER USER 'root'@'localhost' IDENTIFIED BY 'your_new_password';

For older versions:

USE mysql;
UPDATE user SET password=PASSWORD('your_new_password') WHERE User='root';
FLUSH PRIVILEGES;

Replace 'your_new_password' with your desired password.

Step 5: Stop MySQL Safe Mode and Restart Normally

Press Ctrl+C to stop the MySQL safe mode process (if it’s running in foreground), or kill it using:

sudo killall -9 mysqld_safe
sudo killall -9 mysqld

Then start the service again:

sudo systemctl start mysql

Step 6: Test Login to phpMyAdmin

Go to http://localhost/phpmyadmin or your server’s phpMyAdmin URL and log in using:

  • Username: root
  • Password: the new password you just set

If successful, you’re good to go!

Tips for Better Security

  • Avoid using the root account for daily tasks. Create a separate user with limited privileges.
  • Use strong, unique passwords and store them securely using a password manager.
  • Regularly update MySQL/MariaDB and phpMyAdmin for security patches.

Common Issues & Fixes

Issue: Access denied for user 'root'@'localhost'
Fix: Ensure you flushed privileges and restarted the MySQL server after changing the password.

Issue: phpMyAdmin login loop
Fix: Check config.inc.php in your phpMyAdmin directory. Ensure $cfg['Servers'][$i]['auth_type'] is set to 'cookie'.

Conclusion

Resetting a forgotten phpMyAdmin password isn’t difficult when you follow the correct steps. Always remember to restart the MySQL service after resetting the password and ensure your configuration files are properly set. Keeping your credentials secure and using non-root accounts for regular usage can further enhance your database security.

Fix “Can’t Upgrade Due to Low Disk Space on /boot” in Linux

Learn how to resolve the ‘low disk space on /boot’ error during Linux upgrades. Follow step-by-step solutions to free up /boot and complete your system updates.

Your /boot partition is filled with old kernels. It does that sometimes, not sure why it is never fixed. You can easily remove the old kernels if you know which packages they came in.

First check uname -a to check your current version.

Then run the following command:

dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d;s/^[^ ]* [^ ]* \([^ ]*\).*/\1/;/[0-9]/!d'

This command will list all packages that you no longer need. I don’t like removing them automatically, I like to be in control when it comes to removing kernels. So for every package listed do the following:

sudo apt-get -y purge some-kernel-package

Intermezzo

This intermezzo describes in more detail how the commands work and tries to fix an issue with linux-libc-dev:amd64. Most users can skip this paragraph.

  • dpkg -l 'linux-*' list all packages that have a name starting with ‘linux-‘
  • sed '/^ii/!d; remove all lines that do *not* start withii`
  • uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/" find the current running kernel version
  • /'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d Remove all lines, except the ones containing the current running kernel version number
  • s/^[^ ]* [^ ]* \([^ ]*\).*/\1/ For each line list only the package name
  • /[0-9]/!d Remove lines that do not contain numbers.

To fix Frederick Nord’s issue I think the command can be amended as follows:

dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d;s/^[^ ]* [^ ]* \([^ ]*\).*/\1/;/[0-9]/!d;/^linux-\(headers\|image\)/!d'

It basically adds an extra filter:

  • /^linux-(headers\|image)/!d Delete all lines that do not start with linux-headers or linux-image

/Intermezzo

Where some-kernel-package can be replaced with one of the packages listed. Just beware that you don’t remove the kernel packages that are in current use (as listed by the uname -a) eg. sudo apt-get purge -y linux-headers-3.0.0-12 etc.

It can be automated further using the xargs command, but I don’t like that. It is a personal thing. However, here’s the command to do so:

dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d;s/^[^ ]* [^ ]* \([^ ]*\).*/\1/;/[0-9]/!d' | xargs sudo apt-get -y purge

This is what my /boot looks like, one spare kernel (2.6.38-11) just in case and 3.2.0-24 being current:

$ ls -l /boot
total 59388
-rw-r--r-- 1 root root   730545 Sep 13  2011 abi-2.6.38-11-generic
-rw-r--r-- 1 root root   791023 Apr 25 13:51 abi-3.2.0-24-generic
-rw-r--r-- 1 root root   130326 Sep 13  2011 config-2.6.38-11-generic
-rw-r--r-- 1 root root   140341 Apr 25 13:51 config-3.2.0-24-generic
drwxr-xr-x 3 root root     5120 May 27 17:46 grub
-rw-r--r-- 1 root root 20883146 Oct  1  2011 initrd.img-2.6.38-11-generic
-rw-r--r-- 1 root root 22474219 May  5 09:04 initrd.img-3.2.0-24-generic
drwxr-xr-x 2 root root    12288 Apr 16  2009 lost+found
-rw-r--r-- 1 root root   176764 Nov 27 11:00 memtest86+.bin
-rw-r--r-- 1 root root   178944 Nov 27 11:00 memtest86+_multiboot.bin
-rw------- 1 root root  2656297 Sep 13  2011 System.map-2.6.38-11-generic
-rw------- 1 root root  2884358 Apr 25 13:51 System.map-3.2.0-24-generic
-rw------- 1 root root     1369 Sep 13  2011 vmcoreinfo-2.6.38-11-generic
-rw------- 1 root root  4526784 Sep 13  2011 vmlinuz-2.6.38-11-generic
-rw------- 1 root root  4965776 Apr 25 13:51 vmlinuz-3.2.0-24-generic

And file system usage:

$ df -h /boot
Filesystem Size Used Avail Use% Mounted
/dev/sda5  228M  63M  154M  29% /boot