Ubuntu: Troubleshooting Read-Only File System Failures


Ubuntu: Troubleshooting Read-Only File System Failures.

Read only file system failure

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Read Only File System Failures

A file system is an integral part of an operating system, responsible for managing how data is stored, organized, and accessed on a disk. When a file system is mounted as read-only, it restricts any write operations, meaning users cannot modify, delete, or create new files, but can still view and read existing data. This read-only status is often enforced as a protective measure to ensure data integrity, particularly when the system detects potential issues that could lead to data corruption or loss. For instance, if there is a hardware failure, disk errors, or file system inconsistencies, the system may switch to read-only mode to prevent further damage and safeguard the existing data. This precaution allows users to back up important information and troubleshoot the underlying issues without risking additional data loss.

Thus, while the read-only mode limits certain functionalities, it plays a crucial role in maintaining the stability and reliability of the file system.

Why File Systems Become Read-Only

  • File System Corruption: One of the most common reasons for Linux read only file system errors is file system corruption. This can happen because of unexpected shutdowns, hardware failures, or bugs in the file system itself.
  • Disk Errors: Your disk can go through physical issues, and these issues can be a common factor that leads to a Ubuntu read only file system. For example, bad sectors can prompt the system to remount the file system as read only to prevent further damage.
  • Full Disk: If the disk runs out of space, the file system may switch to read only. This way, it can avoid data overwrites and loss.
  • Kernel Panics or System Crashes: Severe kernel panics or crashes can put the file system in an inconsistent state. As a result of these crashes, the file system remounts as read only upon reboot.
  • Improper Shutdowns: If your system frequently experiences sudden power loss or improper shutdowns, the file system will be in an unstable state. These improper shutdowns result in read-only file systems.

Identifying the Problem

Let’s see how you can identify the problem before fixing it. To identify the problem, you need to first check the system logs, and error messages. Then you need to use specific commands to diagnose the state of your file system.

Checking System Logs and Error Messages

Looking at system logs can give you a lot of insights for diagnosing file system issues. System logs contain detailed information about errors and events that have occurred. So, you can use them to find some clues about why your file system has become read-only.

1. “dmesg” Command: The dmesg command displays messages from the kernel ring buffer, which often includes file system errors. Run the following command to filter out and display relevant error messages:

sudo dmesg | grep -i “ext4”

Replace “ext4” with your file system type.

2. “/var/log” Directory: Logs in the “/var/log” directory can provide additional insights. Check files like “syslog” or messages for entries related to file system issues.

Commands to Determine if Your File System is Read Only

Now, let’s see how you can confirm if your file system is mounted as read only and gather more information about its status.

  • “mount” Command: The mount command lists all mounted file systems and their mount options. In the results of this command you should look for the “ro” (read only) flag.
  • “findmnt” Command: The findmnt command provides a more detailed view of all mounted file systems, including their options.
  • “df” Command: The df command reports file system disk space usage. While it primarily shows disk usage, it can also show if the file system is mounted read only.

Steps to Fix Read-Only File System

Dealing with a Linux read-only file system can be incredibly frustrating, especially when you need to make changes or write new data. Fortunately, you can take several steps to resolve this issue. This guide will walk you through the process of fixing a read-only file system. By following these steps, you can restore your system to normal functionality.

Step 1: Check for Hardware Issues

Before diving into software solutions, let’s first make sure that there are no underlying hardware problems causing the read only file system issue. Start by checking your physical connections, especially if you are using external drives. Loose or damaged cables can lead to write errors and cause the system to mount the drive as read only.

Step 2: Remount the File System

Sometimes, the file system can be remounted as read only due to a temporary issue. You can attempt to remount it as read/write using the following command:


sudo mount -o remount,rw /mount/point

Replace /mount/point with the actual mount point of your file system. This command forces the system to remount the file system with read/write permissions. If this resolves the issue, you can assume it was likely a temporary glitch.

Step 3: Run a File System Check

A very common cause of this issue is file system corruption. To check and repair the file system, you can use the fsck (file system check) utility. Before running fsck, make sure that the file system is unmounted:

sudo umount /mount/point

Next, run the fsck command:

sudo fsck -y /dev/sdX1

Replace /dev/sdX1 with the appropriate device identifier for your file system.

After the check is complete, remount the file system:

sudo mount /dev/sdX1 /mount/point

Step 4: Review System Logs

If the issue persists, reviewing system logs can provide insights into the root cause. Use the dmesg command to view kernel messages related to the file system:

dmesg | grep -i “read-only”

Look for any relevant error messages that could indicate why the file system is being mounted as read only.

Step 5: Update the File System Table (fstab)

If the file system consistently mounts as read only on reboot, you might need to update your /etc/fstab configuration. Open the /etc/fstab file with a text editor:

sudo nano /etc/fstab

Now, make sure that the file system entry is correctly configured with the defaults option or explicitly set to “rw” (read/write):

/dev/sdX1 /mount/point ext4 defaults 0 2

As the final step, save the changes and reboot your system:

sudo reboot

Following these steps should resolve the read-only file system issue on your Linux system. Whether it’s a temporary glitch, file system corruption, or a misconfiguration in /etc/fstab, these solutions address the most common causes and fixes. If the problem persists after trying these solutions, consider seeking further assistance from Linux support communities or professional help.

Preventive Measures

There are some effective preventive measures that you can take to avoid encountering a Linux read only file system issue in the future. This section reviews several strategies to maintain a healthy file system in your Linux environment.

Regular System Updates and Backups

Make sure your system is always up-to-date with the latest patches and updates. This helps in preventing bugs and vulnerabilities that could cause file system errors.

Proper Shutdown Procedures

Always shut down your system properly to prevent abrupt power-offs which can lead to file system corruption. Also, avoid forced shutdowns by holding the power button unless it’s the only option.

Monitoring Disk Health

If you regularly monitor the health of your disk, you can prevent Linux read only file system errors. You can regularly run file system checks using fsck to identify and fix potential issues before they become serious.

These steps will hopefully help you in reducing the likelihood of experiencing a read-only file system error in Linux.

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