Ubuntu 16.04 read-only flash drive. Linux read-only file system

Although it is superior to Windows in some respects, it is also capable of ruining the user’s mood by producing errors. One of these is the inaccessibility of the file system. Moreover, this applies to both regular flash drives and hard drives in some situations. The problem can be solved. However experienced users they don’t always know how to fix the error when Ubuntu displays: “The file system is read-only.” We tried to give the answer in this article.

So when you want to put everything together, you have to write. Explode. Under no circumstances should you read files this way. The meaning of such a code can be summarized as simple comparison: Package for immediate unpacking only. It serves no purpose and it consumes necessary time.

It is also worth mentioning the discontinuation of the so-called “According to You from Computer Science”. The solution is best illustrated with an example. However, the disadvantage of this solution is that after writing the code, we may end up buried in blocks if we lose the main thread of the program, and we cannot think of all the possible situations that could happen.

There can be several reasons for problems with accessing files in Ubuntu.

First of all, you should check whether this file system is working correctly. In the case of a flash card, this is easy to do. Try opening it from a Windows computer. Another system can quickly find problems with the drive. The same goes for memory cards, Chinese players and other cheap storage media. Often it may be them.

This operation is performed open function. It is essentially a string of bits in which each bit or group of bits has a specific meaning. After using a file, it must be closed using a function. Reading data from an open file is done using a function.

If it is exactly at the end of the file, the function returns zero, and if there is an error, it returns zero. Write and read operations to and from a file are performed at a specific position in the file and are considered the current position. For example, each read operation updates the current position indicator by increasing its number of bytes read.

Data writes look similar to data reads. Miscellaneous is just the destination of the data. It returns the number of bytes in the file, and we can use this to monitor whether the append operation actually succeeded. The function takes two parameters: the file name and the text to write, and "firm" does not mangle the binary data.

Let's ask ourselves what if we need to add additional content. This script will now append data to the file rather than overwrite it. In many cases it is useful to know what we have in our catalogs. We can get it using a family of functions that provide us with a variety of information about files. They all assume the filename.

In the case where the problem is HDD, the check will be much more difficult. If your computer has two systems, check if your HDD is working properly on Windows. These methods will allow you to determine the source of the malfunction.

Formatting

In many cases, simply formatting the file system helps restore functionality. This is especially easy to do on a flash drive. True, we are not always ready to part with the information that is already on it. Transfer all data to your computer under Windows control and format the problematic drive.

In case of error, the function returns. Any use system function is very important for checking the value it returns. Search for file attributes. A pointer indicating the memory location in which the state function returns this information must be specified as the second parameter of the function. The memory area must be reserved in advance to preserve the state structure.

Appendix: Other functions for working with directories and files

Directories are essentially files with a special format. Checking files in a directory looks like this: Each call to these functions returns a pointer to a heavy structure that will find the read directory read information. Directory entries will be transferred one by one until the last record. As shown above, the only information that can be extracted from the direct structure is the name of the directory entry. This is true both for modified user data, that is, for his work and for system data.

When using them, we must keep performance in mind. Reading all the data on disk is slow, so try to compress as much as possible from a single function call. Therefore we must write a mechanism to check if compilation can be run or if it is not needed. Everything seems to be correct - the script communicates all the issues correctly. But it's too slow because we overloaded it big amount hard drive links. If you run it on a high traffic site, it will perform worse than other scripts.

It’s unlikely that anyone would dare to do this with a disc. Formatting can destroy a lot important information. Moreover, if the Ubuntu file system is damaged, the problem must be looked for elsewhere.

This is even recommended, especially if you plan to replace your computer from time to time. Therefore, the data used cannot be changed. This does not mean it is enabled, but the system recognizes and can use persistence if the environment is configured for it. Mode selection is made in the first seconds after startup, you have the choice to launch in constant or non-real mode.

Continuous mode is when you want to disable data saving. By default, this utility works in a simplified way called "assistant". "Expert" mode is described in detail below and is not intended for those users who are less well suited to computers. Assistant mode begins by detecting external and internal drives. If one or more are found external drives, the utility prompts you to activate saving on this drive or you select the required external drive from the list. A negative answer will force the prompt to use that internal drive.

Let's try to change it a little. Instead of performing hundreds of new functions every time, we make the most of the data we already have. This is the correct philosophy for working with files. We devoted a very large chapter to files. Significantly more powerful and powerful tool is a database. This issue is discussed in the next section of this book. But should the files be thrown away anyway? Contrary to indications, reading records from a database is generally slower than a file, and for basic application options that don't require complex sorting and extensive relationships, it may be tempting to replace them with files.

Checking for errors

You can check the disk for errors not only on Windows. Ubuntu also has enough arsenal for this. This can be done using commands or using a special application. First, let's look at a method that uses standard tools.

We look through the list of drives:

Checking a specific drive:

Typically, from the user's point of view, file systems have an organization based on the ideas of files and directories. Files are objects that encapsulate certain types of information, as well as directory group files and other directories within them. Any file or directory can be identified by its name, which is specified absolutely as a pathname or relative to the current directory.

For fixed and floppy disks, information is stored using their magnetic properties. A hard disk contains several storage folders inside, while a floppy disk consists of one floppy disk. The face of the disk is divided into tracks, which are concentric circles in which information can be stored. Tracks are divided into sectors, a sector reporting a fixed amount of information. Reading and writing information on a disk is performed at the data block level. A block may consist of one or more sectors.

hdparm -i /dev/sdf | grep Model

The example uses sdf, but your disk name may be different.

If the volume was mounted, then before checking, this action must be canceled:

Now we check the volume for bad blocks - problem areas:

badblocks -s /dev/sdf1 > /root/badblock

Progress will be displayed as a percentage.

The hard drive can be partitioned by the user, with each partition behaving at the user level as a separate drive. The partition stores the file system, which means that on one physical disk multiple file systems can be found. For ordinary personal computers Partition information is stored at the beginning of the disk in what is called a partition table. It contains 4 entries that remember the positions, sizes and types of disk partitions. The stored memory partitions at the beginning of the disk are called primary partitions, which can obviously contain up to four.

Now we mark bad blocks so that the system stops using them:

e2fsck -l /root/badblock /dev/sdf1

This method, in theory, should help fix problems with any type of media. If scanning disks for errors does not help, then it’s time to use a convenient utility - GParted.

GParted

However, it is possible that new table partitions are created inside any primary partition, referencing partitions that are physically inside the current partition and are called extended partitions. The first sector of a partition or disk that contains the system is called the boot sector. It contains the following information.

Directories are stored in special structures, such as tables, in which each entry represents a file. In fact, the directory is saved as regular file, but contains information about other files. There is a root directory stored in the file allocation table, which has a limited size.

First, you need to install this program. This is easy to do using the command:
sudo apt-get install gparted
Open GParted. All media will be displayed in front of us. Among them there should be a problematic one that is inaccessible - if the utility sees errors, it will mark it with an exclamation mark.
Now open our disk and click on the “Partition” button located at the top.
In the drop-down menu, select “Check for errors.” The program will scan the disk and possibly find problems, after which the file system will become read-only.

Access rights

Finally, last reason The reason why we lose access to data management on media is due to violated rights. Experienced users using root mode may also encounter this problem. When do we use various commands without fully understanding their essence, or we launch programs with extended rights, the system may mistakenly block access.

Directory entry structure. File distribution table. It is essentially a picture-like structure that stores within it linked lists that indicate the clusters that make up the files. The number of the first cluster of a file is stored, as already noted, in the directory corresponding to this file.

Example. The index node area is a fixed size when the file system is created and contains an entry for each file that can be created in that support. The swap area is reserved for storing process images when temporarily removed from memory to make room for other processes. However, as a rule, separate partitions are used for the swap area. Structure of Inodes An inode contains important information about the file associated with it. Rights have three types and are grouped into three categories: rights of a user on a group of users - rights of a user in a group of owners of others - rights of all other users.

The last area contains blocks in which files are stored.
The file name number of the index node associated with the file.
Each file has only one inode.
Can see more entries in a directory pointing to the same index node.
Determines the owner of the file group file ID of the file permissions.

Such a link is considered by the user as a file with its own own name, but actually refers to another file on disk.

After which we see a message from Ubuntu: “The file system is read-only.” Special commands will help you fix this problem.

As universal method The command here is suitable:

You must enter your username instead. The chown command is responsible for changing access rights to a folder. The –R attribute means that this section can only be read by the user. Sudo reverts these changes. In the example, the problem was in the home partition; if you have problems with the flash drive, then you should enter its directory.

Any operation performed on a referenced file will have an actual effect on the referenced file. If removal is required, the effect depends on the type of link. There are two types of links. Physical symbolism. . Symbolic links are actually separate files, marked special code, which contains full name specified file. Removing them does not affect the file. They can link to directories, as well as files and folders from another partition or another drive, but have the disadvantage that a separate index node must be created for them and, in addition, occupy disk space through their content.

The Ubuntu file system works on slightly different principles than on Windows. Therefore, any disks under its control behave differently. Because of this, new errors arise that cannot be encountered on Windows.

Creating links to files or folders is done using the B command. Special files that point to drives or partitions are used in an operation called mounting a file system. This means that after installation the entire directory and file structure file system will be located in this directory.

The mechanism is particularly effective because it offers the ability to have a unitary directory structure that groups files across multiple partitions or drives. Data without any parameters displays file systems that are currently installed on the system.

Now we know how to solve the problem regarding disc editing problems. The issue may be either a malfunction of the devices or an incorrect definition of rights. The main thing is to correctly identify the problem and fix it. Fortunately, this is not the most serious of all errors, although it can cause trouble for the user.

Although it is superior to Windows in some respects, it is also capable of ruining the user’s mood by producing errors. One of these is the inaccessibility of the file system. Moreover, this applies to both regular flash drives and hard drives in some situations. The problem can be solved. However, even experienced users do not always know how to fix the error when Ubuntu displays: “The file system is read-only.” We tried to give the answer in this article.

The index area consists of inodes that have the same structure. The size of the field depends on the number of inodes it contains. This number is determined when the file system is created and cannot be changed. Inodes contain information about the file. Each inode can describe at most one file.

Index descriptors contain the following information about a file. Address information - 40 bytes. . The first 10 addresses are the direct addresses of the first 10 data blocks of the file. If the file is larger than 10 blocks, indirect blocks are used. Indirect blocks are located in the data field, but contain block numbers rather than file data. The eleventh address contains the dummy block number, which contains the numbers of the next data blocks of the file. This is called one indirect addressing. The twelfth block contains the indirect block number, which contains the number of indirect blocks that already contain data block blocks.

There can be several reasons for problems with accessing files in Ubuntu.

Automatic installation of partitions

Disables executables executable files in the file system. Another security option. Unconditionally unmounting a file system may result in a system crash or data corruption on the file system. Then run the command to mount the partition in the existing directory.

To unmount the drive, run the command. The file system is a mechanism for organizing various types storage and presentation to the user. Each file system consists of several elements. The launch block contains information necessary for the system to access the file system. The data block is the area for our data. The file system can be mounted or unmounted. Displays the amount of free and used space in the file system.

This is called double indirect addressing. Triple indirect addressing is implemented through the thirteenth block. The list of free blocks is provided via linked list. Directories are represented as files, in which for each file contained in the directory, a two-line structure is written: an inode and a file name.

The boot block occupies one block and contains the program that starts loading the operating system. The remaining blocks are grouped into groups of the same size. Each group contains part of the file system and a copy of the global system systems critical to system integrity—the superblock and group descriptors.

If the problem is the hard drive, it will be much more difficult to check. If your computer has two systems, check if your HDD is working properly on Windows. These methods will allow you to determine the source of the malfunction.

Formatting

In many cases, simply formatting the file system helps restore functionality. This is especially easy to do on a flash drive. True, we are not always ready to part with the information that is already on it. Transfer all the data to a computer running Windows and format the problematic drive.

As a target we can specify the name of the device or its mount point. Mount mount options. In previous chapters, we often had different data reads on the hard drive. It's time to collect information about them and systematize them. The first thing to keep in mind is performance. All links to the file system are quite slow and often even represent bottleneck at the speed of our code. So you should try to do the best you can and cache the results of some of them so that subsequent code can reference them.

Group descriptors are written in each group in a series of numbers one after the other. Each inode contains information about which blocks belong to the file. This is achieved by using pointers that point to blocks in the group data field. Returns - with a success number greater than or equal to zero, representing a file descriptor from the system tables.

Opens a file; if the file does not exist, it first creates it using the third argument. Positioning the primitive in the file. On success, a new file handle is returned. Creating a hierarchical file system organization - creating and destroying a directory, creating and destroying links, changing the current directory. Destruction of the directory; the directory must not contain any files.

It’s unlikely that anyone would dare to do this with a disc. Formatting can destroy a lot of important information. Moreover, if the Ubuntu file system is damaged, the problem must be looked for elsewhere.

Each file access must begin with opening it. Then in a loop we download a one kilobyte file. In this way, data can be processed "in parallel" with reading. Once complete, your connection to the file should be closed. From the above code we can throw a loop and load everything in one go.

Pay attention to the quality of the examples given. Rename the files we link to some that don't exist. The first one will send us a wave of alerts within 30 seconds, the second one will make “only” a few of them. Therefore, we must prepare everything so that we can control the messages ourselves. Time to create primitive error handling. It should provide us with a link to the file, that is, the value of the resource.

Changes current directory processes; The old current directory of the process is returned and the inode of the new directory is loaded. All directories on the road must exist, and the process has execution rights to them. When rigid connection the file is also guaranteed and the original name is destroyed, but the symlink is not. In fact, it doesn't even check for presence source file when creating a symbolic link. A symbolic link is interpreted when an attempt is made to access a file through it. Additionally, a symbolic link can be created across file system boundaries to a regular file, special file and catalogue.

Checking for errors

You can check the disk for errors not only on Windows. Ubuntu also has enough arsenal for this. This can be done using commands and using special application. First, let's look at a method that uses standard tools.

We look through the list of drives:

Checking a specific drive:

The specified file name is excluded from the file system; the number of hard link fields in the file inode is reduced by 1; if this number becomes 0, the file is destroyed. To change file permissions, the process executing this primitive must be an administrator or owner of the file.

This guide is intended for advanced users. You must have administrator rights to connect other devices. Let's list all available disks and partitions. The result will look like this. This can be any empty directory, even in your home directory.

hdparm -i /dev/sdf | grep Model

The example uses sdf, but your disk name may be different.

If the volume was mounted, then before checking, this action must be canceled:

Now we check the volume for bad blocks - problem areas:

badblocks -s /dev/sdf1 > /root/badblock

Progress will be displayed as a percentage.

Is this only an active ringtone?

you can find full list on the man page using.

Is only the file downloaded?

Did you save this time, money? Did it help solve the problem? Are you ready to provide a symbolic reward for further development? There are over 000 lines, tips and tricks, including many different patterns.

Hard drives and other storage spaces are attached under the letters, for example, this is not something special, although it is a fact that separate disks don't have a common top point for me, strange. In fact, the desktop is nothing more than a folder located on system disk somewhere in the user's folder. Elsewhere there are several hidden system files to add to the confusion. You have a "shortcut" is the file type of a symlink, you have a directory is the file type of a directory, a process is the file type of a process.

Now we mark bad blocks so that the system stops using them:

e2fsck -l /root/badblock /dev/sdf1

This method, in theory, should help fix problems with any type of media. If scanning disks for errors does not help, then it’s time to use a convenient utility - GParted.

GParted

On this system, in order to read a 3.5-inch floppy disk, it must be installed first. Before you start editing, he will give you necessary knowledge. You don't need to list all the devices you have. Lines starting with # are comments.

Comments usually include information about the file, or thus signify lines that are temporarily excluded from the file operation. In the third, we have headers that define what the following information is. File System - Identifies the device or file system to be installed and the location in which it is located.

First, you need to install this program. This is easy to do using the command:
sudo apt-get install gparted
Open GParted. All media will be displayed in front of us. Among them there should be a problematic one that is inaccessible - if the utility sees errors, it will mark it with an exclamation mark.
Now open our disk and click on the “Partition” button located at the top.
In the drop-down menu, select “Check for errors.” The program will scan the disk and possibly find problems, after which the file system will become read-only.

Access rights

Finally, the last reason why we lose access to data management on media is because of infringed rights. Experienced users using root mode may also encounter this problem. When we use various commands without fully understanding their essence, or run programs with extended privileges, the system may mistakenly block access.

Mount point is the location where the device should be installed. We will refer to this location when using the device. Each operating system has its own file system that it prefers and runs on. Dump - The specified value indicates that the file system should be offline. The default value is 0, which means you do not need to unmount the filesystem.

A value of 1 means that the partition must be checked first. In contrast, a value of 2 means that the disk or partition should be checked further. Examples of headings were mentioned. They may have different names, but the order of the values must be the same!

After which we see a message from Ubuntu: “The file system is read-only.” Special commands will help you fix this problem.

The following command is suitable as a universal method:

Before installing any device, you need to know how it is identified in the system. Knowing where a specific hard drive is located, we can find its partitions. Also note that basic and advanced sections can be up to four. The program will display about the partitions on this disk.

After reading the above text, you can now mount partitions and devices. To mount the device you can use the command. You can expand on this. This mount makes sense for media other than hard drives. If the system does not detect the device after installation, it must be installed by the device. Programmers had to write “again,” and the driver in early versions caused errors that could lead to data loss.

This command will mount the file system in read-only mode. Then, preferably at the end, add a ruler. You should write this on one line. These parameters are no longer described - you read them at the beginning of this article. Also keep in mind that the mount locations must exist!

There are several reasons why it is useful to keep some directories on separate file systems. The directory where the file system should be installed. IN simplest form it is used as follows. # Mount point mount device.

How to allow writing to read-only folders in a program Total Commander on Android. We wrote about a wonderful program, file manager for Android Total Commander, which can easily replace all other Android programs of this kind (ASTRO, Root Explorer, ES Explorer).

Total Commander is Russified, has root support, the ability to connect plugins, two-panel mode, and is absolutely free for life. That is, completely, there is also no advertising.

However, upon closer acquaintance with the program, it turned out that mounting system partitions for recording in Total Commander it just won’t work. IN Root program Explorer, for example, this can be done by clicking on the " Mount RW"There is no such button or similar menu item in Total Commander.

However, as it turned out, there is a way out of this situation thanks to wide possibilities program settings. And today we will tell you how to add the button we need to the program button panel within one minute.

Instructions:

1. Launch Total Commander and, if necessary, open the button panel by clicking on:

2. You can add a button to the panel by clicking on:

3. In the window that opens, select “Function type:”

4. Select Internal Team

5. In the "Command" field, select "119 Remount"

6. Click on OK / Apply

Although superior in some ways Windows settings, but is also capable of spoiling the user’s mood by producing errors. One of these is the inaccessibility of the file system. Moreover, this applies to both regular flash drives and hard drives in some situations. The problem can be solved. However, even experienced users do not always know how to fix the error when Ubuntu displays: “The file system is read-only.” We tried to give the answer in this article.

There can be several reasons for problems with accessing files in Ubuntu.

First of all, you should check whether this file system is working properly. In the case of a flash card, this is easy to do. Try opening it from a Windows computer. Another system can quickly find problems with the drive. The same goes for memory cards, Chinese players and other cheap storage media. Often it may be them.

Formatting

In many cases, simply formatting the file system helps restore functionality. This is especially easy to do on a flash drive. True, we are not always ready to part with the information that is already on it. Transfer all the data to a computer running Windows and format the problematic drive.

Checking for errors

We look through the list of drives:

Checking a specific drive:

hdparm -i /dev/sdf | grep Model

The example uses sdf, but your disk name may be different.

If the volume was mounted, then before checking, this action must be canceled:

Now we check the volume for bad blocks - problem areas:

badblocks -s /dev/sdf1 > /root/badblock

Progress will be displayed as a percentage.

Now we mark bad blocks so that the system stops using them:

e2fsck -l /root/badblock /dev/sdf1

This method, in theory, should help fix problems with any type of media. If scanning disks for errors does not help, then it’s time to use a convenient utility - GParted.

GParted

First, you need to install this program. This is easy to do using the command:
sudo apt-get install gparted
Open GParted. All media will be displayed in front of us. Among them there should be a problematic one that is inaccessible - if the utility sees errors, it will mark it with an exclamation mark.
Now open our disk and click on the “Partition” button located at the top.
In the drop-down menu, select “Check for errors.” The program will scan the disk and possibly find problems, after which the file system will become read-only.

Access rights

After which we see a message from Ubuntu: “The file system is read-only.” Special commands will help you fix this problem.

The following command is suitable as a universal method:

sudo chown -R : /home/