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Solving Permission Problems on External Media in Ubuntu

Ubuntu 17

In this article, we will delve into the common issue of permission problems when trying to access external media in Ubuntu. We will explore possible solutions, including enabling ACL (Access Control List) permissions, mounting Windows drives with access permission, and deleting and recreating the problematic directory.

Quick Answer

To solve permission problems on external media in Ubuntu, you can try enabling ACL permissions, mounting Windows drives with access permission, or deleting and recreating the problematic directory.

Understanding the Problem

When dealing with external media in Ubuntu, you might encounter a situation where you are unable to access files in the /media/user folder. Despite the /media/casper/externaldrive directory having the correct permissions, access remains blocked. This issue often arises because the /media/user folders are managed by root and have ACL permissions. However, your system may not display the ACL permissions.

Solution 1: Enable ACL permissions

ACL permissions provide an additional layer of access control for files and directories. If your filesystem is not showing ACL permissions, you might need to enable them.

Checking ACL Package

First, check if the acl package is installed on your system by running the following command:

apt-cache policy acl

This command will display the installed version of the ACL package, if any.

Checking Filesystem Mount Options

Next, verify if your filesystem is mounted with the acl option. Replace sdxY with your filesystem identifier in the following command:

sudo tune2fs -l /dev/sdxY | grep "Default mount options:"

If the output does not include acl, your filesystem is not mounted with the ACL option.

Enabling ACL Permissions

To enable ACL permissions, add acl to the default mount options using the following command:

sudo tune2fs -o acl /dev/sdxY

Alternatively, you can add acl to the options for the root partition line in the /etc/fstab file.

With ACL permissions enabled, you can use the setfacl command to add permissions for yourself. Replace username with your actual username in the following command:

sudo setfacl -m u:username:rx /media/casper

This command sets read and execute permissions for the user on the /media/casper directory.

Solution 2: Mount Windows Drive with Access Permission

If the external media is a Windows NTFS drive, you cannot use the chmod command to change permissions. Instead, you can mount the drive with access permission.

Finding the Drive Name

Open the /etc/mtab file and find the drive name.

Mounting the Drive

Mount the drive using the following command:

sudo ntfs-3g /dev/sda4 /media/"$USER"

This command mounts the NTFS filesystem at /dev/sda4 to the /media/user directory.

Solution 3: Delete and Recreate Directory

If the above solutions do not work, you can try deleting and recreating the problematic directory.

Deleting the Directory

First, unmount and unplug any mounted disks in /media/casper. Then, delete the directory using the following command:

sudo rmdir /media/casper

Recreating the Directory

The next time you attach a USB drive or insert a CD/DVD, Ubuntu will recreate the directory with the correct permissions.

Conclusion

Permission problems on external media in Ubuntu can be a nuisance, but with the right approach, they can be solved. By enabling ACL permissions, mounting Windows drives with access permission, or deleting and recreating the problematic directory, you can regain access to your files. Remember to replace placeholder values in the commands with your actual values.

How do I check if the `acl` package is installed on my Ubuntu system?

You can check if the acl package is installed on your Ubuntu system by running the command apt-cache policy acl. This command will display the installed version of the ACL package, if any.

How can I verify if my filesystem is mounted with the `acl` option?

To verify if your filesystem is mounted with the acl option, you can run the command sudo tune2fs -l /dev/sdxY | grep "Default mount options:", replacing sdxY with your filesystem identifier. If the output does not include acl, your filesystem is not mounted with the ACL option.

How can I enable ACL permissions on my Ubuntu system?

To enable ACL permissions, you can add acl to the default mount options of your filesystem using the command sudo tune2fs -o acl /dev/sdxY, replacing sdxY with your filesystem identifier. Alternatively, you can add acl to the options for the root partition line in the /etc/fstab file.

How can I add ACL permissions for myself on a specific directory?

Once ACL permissions are enabled, you can use the setfacl command to add permissions for yourself. For example, to set read and execute permissions for the user on the /media/casper directory, you can run the command sudo setfacl -m u:username:rx /media/casper, replacing username with your actual username.

Can I change permissions on a Windows NTFS drive using the `chmod` command?

No, you cannot change permissions on a Windows NTFS drive using the chmod command. Instead, you can mount the drive with access permission using the ntfs-3g command.

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