After upgrading your Ubuntu operating system from 21.04 to 21.10, you may encounter an error message saying “cannot attach cgroup program: Operation not permitted”. This error can prevent certain applications, such as Chromium and Firefox, from starting. This article will guide you through the steps to fix this issue.
Understanding the Error
The error “cannot attach cgroup program” is typically related to the cgroup hierarchy. Cgroup, or control groups, is a Linux kernel feature to limit, police and account the resource usage for process groups. In the case of this error, the cgroup program is unable to attach, possibly due to an outdated kernel being loaded by GRUB or issues with apparmor.
Checking Your Kernel Version
The first step in resolving this issue is to ensure that your GRUB is loading the correct, updated kernel. You can check your current kernel version by using the following command in the terminal:
This command will return the version of the kernel that your system is currently using. If the kernel version returned is not the most recent one, you will need to update it.
Updating Your Kernel
To update your kernel, you can use the following command:
sudo apt-get update && sudo apt-get upgrade
This command will update the list of available packages and their versions, and then upgrade the outdated packages. After running this command, restart your system and check your kernel version again. If the kernel version is now updated, try starting the applications that were causing the error.
If updating the kernel doesn’t resolve the issue, the next step is to reconfigure Apparmor. Apparmor is a Linux kernel security module that allows the system administrator to restrict programs’ capabilities with per-program profiles. You can reconfigure it using the following command:
sudo dpkg-reconfigure apparmor
When prompted, select “ok”. After reconfiguring Apparmor, restart your system and try starting the applications again.
Enabling cgroup v1
If the above solutions do not work, you can try adding the kernel parameter “systemd.unified_cgroup_hierarchy=0” at boot time to enable cgroup v1. This can be done by editing the GRUB configuration file:
sudo nano /etc/default/grub
Find the line that starts with
GRUB_CMDLINE_LINUX_DEFAULT and add
systemd.unified_cgroup_hierarchy=0 to the end of the quoted text. Save and exit the file, then update GRUB with the following command:
After updating GRUB, restart your system. This solution forces the system to use cgroup v1, which may resolve the issue. However, this is a temporary solution and it is recommended to investigate further.
The “cannot attach cgroup program” error can be a frustrating issue, but the steps outlined in this article should help you resolve it. If you continue to experience problems, it may be necessary to report the bug to the Ubuntu community for further assistance. Remember, it’s always important to keep your system updated and to regularly check for any potential issues that might arise after an upgrade.
To check your kernel version in Ubuntu, open the terminal and run the command
uname -r. This will display the kernel version currently being used by your system.
To update your kernel in Ubuntu, open the terminal and run the command
sudo apt-get update && sudo apt-get upgrade. This will update the list of available packages and their versions, and then upgrade the outdated packages, including the kernel. After the update is complete, restart your system to apply the changes.
To reconfigure Apparmor in Ubuntu, open the terminal and run the command
sudo dpkg-reconfigure apparmor. When prompted, select "ok". This will reconfigure Apparmor with the default settings. After the reconfiguration is complete, restart your system.
To edit the GRUB configuration file in Ubuntu, open the terminal and run the command
sudo nano /etc/default/grub. This will open the GRUB configuration file in the nano text editor. Make the necessary edits, save the file, and exit the editor. Remember to run
sudo update-grub after making any changes to the GRUB configuration file for the changes to take effect.
Enabling cgroup v1 in Ubuntu forces the system to use the cgroup v1 hierarchy, which can help resolve the "cannot attach cgroup program" error. This is a temporary solution and should be used if other methods do not work. However, it is recommended to investigate further and report the issue to the Ubuntu community for assistance.