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- Announcements
- Updating Some Image Pip Package Management Tools for CentOS 7
- CentOS 8 End of Maintenance
- Discontinuation of Support for SUSE Commercial Images
- Price Reduction in Selected Availability Zones
- OrcaTerm Proxy IP Addresses Updates
- Pay-as-you-go Price Adjustments for Standard S3 CVMs in the Silicon Valley Region
- Vulnerability repairing for Linux images
- Stopping supporting for Ubuntu 10.04 images
- Solution to Tomcat Start Failure on Ubuntu14.04
- Upgrading Virtio network card drive for Windows CVMs
- About Configuration of Security Group Port 53
- Windows Server 2003 System Images End of Support Announcement
- End of Support for Windows Server 2008 R2 Enterprise Edition SP1 64-bit System Images
- Product Introduction
- Purchase Guide
- Getting Started
- Operation Guide
- Operation Guide Overview
- Use Limits
- Convenience Features
- Instances
- Creating Instances
- Managing Instance Launch Template
- Batch Sequential Naming or Pattern String-Based Naming
- Logging In to Linux Instances
- Logging in to Windows instance
- Adjusting Configuration
- View Instance Details
- Renaming Instances
- Resetting Instance Password
- Managing Instance IPs
- Changing Instance Subnet
- Changing Security Group
- Conversion from Pay-As-You-Go to Monthly Subscription
- Searching for Instances
- Exporting Instance List
- Renewing Instances
- Starting Up Instances
- Shutting Down Instances
- Restarting Instances
- Reinstalling System
- Using Tencent Cloud Automation Tools to execute commands
- Terminating/Returning Instances
- Enabling Instance Termination Protection
- Instance Repossession or Recovering
- Spot Instances
- Querying the Repossession Status of a Spot Instance
- No Charges When Shut Down for Pay-as-You-Go Instances
- Managing Roles
- Enabling and Disabling Hyper-Threading
- Reserved Instances
- Images
- Migrating Servers
- Maintenance Tasks
- Cloud Disks
- Networking
- Security
- Security Groups
- Protection of Sensitive Operations
- Managing Login Password
- Managing SSH Keys
- Spread Placement Group
- Unblocking Port 25
- Tags
- Monitoring and Alarms
- Sample Console Configuration
- Best Practice
- Best Practices
- Choosing the CVM Model
- Setting up a Website
- Building an Environment
- Building a Website
- Building an Application
- Building a Visual GUI
- Data Backup
- Uploading Local Files to CVM
- Copying Local Files to CVMs
- Uploading Files from Windows to a Windows CVM via MSTSC
- Uploading Files from MacOS to Windows CVM Using MRD
- Uploading Files from Linux to Windows CVM using RDP
- Uploading files via WinSCP to a Linux CVM from Windows
- Uploading Files from Linux or MacOS to Linux CVM via SCP
- Uploading Files from Linux to a CVM Using FTP
- Uploading Files from Windows to a CVM Using FTP
- Other CVM Operations
- CVM Access to COS via a Private Network
- Best Practices for Boot Mode Legacy BIOS and UEFI
- Recovering Data on Linux CVMs
- Managing Disk Space on Windows CVMs
- Changing Kernel of a Linux Instance Manually
- Setting Up Windows-based AD Domain on a CVM
- Network Performance Test
- High-throughput Network Performance Test
- Using USB/IP to Share USB Devices in Linux
- Using RemoteFx to Redirect USB Devices in Windows
- Using AVX-512 Instructions to Accelerate AI Applications on CVM
- Building Tencent SGX Confidential Computing Environment
- Configuring Persistent Memory in M6p Instances
- Calling Cloud APIs via Python to Share Custom Images in Batches
- Operations Guide
- Initializing Data Disks
- Environment Configurations
- Installing Software
- User Data
- Work with Operating Systems
- System Activation
- System Updates
- System Shutdown
- Configuring High-performance Power Management
- Windows Recovery Mode
- Updating the Virtio ENI Driver
- Modifying SID
- Modifying VNC Resolution
- Ensuring Unique SIDs for CVMs Using Sysprep
- Use of the atop Monitoring Tools by Linux Instances
- Introduction to Linux Kernel Parameters
- Others
- Troubleshooting
- Instance-Related Failures
- CVM Login Failures
- Windows Instance Login Failures
- Windows Instance Login Failures
- An authentication error occurred when you tried to log in to a Windows instance remotely
- Failed to Reset the CVM Password or the CVM Password Is Invalid
- Connection to a Windows CVM through Remote Desktop was denied
- Requires network-level identity verification
- Problems occurred when you tried to log in to a Windows CVM remotely on Mac
- Failed to log in to a Windows CVM due to high CPU and memory usage
- Failed to connect to a remote computer through Remote Desktop
- Credentials Not Work
- Windows instance: no remote Desktop license server can provide license
- Remote Login Failure Due To Port Issues
- Linux Instance Login Failures
- Linux Instance Login Failures
- Unable to Log in to a Linux Instance via SSH Key
- Failing to log in to a Linux CVM due to high CPU and memory usage
- Remote Login Failure due to Port Issues
- VNC Login Error (Module is Unknown)
- VNC Login Error (Account Locked due to XXX Failed Logins)
- VNC Login Error (Login Failed with Correct Password)
- VNC or SSH Login Error (Permission Denied)
- Login Failure Due to /etc/fstab Configuration Errors
- sshd Configuration File Permissions
- Infinite Loop Call in /etc/profile
- Login Failure Due to Server Isolation
- Login Failure Due to High Bandwidth Occupation
- Remote Connect Failure Due to Security Group Settings
- Troubleshooting Linux Instance Issues via VNC and Rescue Mode
- Failed to shut down or restart a CVM
- Network Namespace Creation Failure
- Kernel and IO Issues
- Missing System bin or lib Soft Link
- Suspected Infection with Virus
- "no space left on device" Error During File Creation
- Linux CVM Memory Issues
- Network Related Failures
- Instance-Related Failures
- API Documentation
- History
- Introduction
- API Category
- Making API Requests
- Region APIs
- Instance APIs
- DescribeInstances
- DescribeInstanceFamilyConfigs
- DescribeZoneInstanceConfigInfos
- DescribeInstanceTypeConfigs
- DescribeInstancesOperationLimit
- DescribeInstanceVncUrl
- InquiryPriceRunInstances
- InquiryPriceResetInstance
- InquiryPriceResetInstancesType
- InquiryPriceResizeInstanceDisks
- RunInstances
- StartInstances
- RebootInstances
- StopInstances
- ResetInstance
- TerminateInstances
- ResetInstancesType
- ResizeInstanceDisks
- ResetInstancesPassword
- ModifyInstancesAttribute
- ModifyInstancesProject
- InquirePricePurchaseReservedInstancesOffering
- DescribeReservedInstancesConfigInfos
- DescribeInstancesStatus
- PurchaseReservedInstancesOffering
- Cloud Hosting Cluster APIs
- Placement Group APIs
- Image APIs
- Key APIs
- Security Group APIs
- Network APIs
- Instance Launch Template APIs
- Data Types
- Error Codes
- FAQs
- Related Agreement
- Glossary
Changing Kernel of a Linux Instance Manually
Last updated: 2024-01-06 17:43:10
Overview
Bottleneck Bandwidth and Round-trip propagation time (BBR) is a TCP congestion control algorithm developed by Google in 2016. It helps significantly improve the throughput and the TCP connection latency of Linux servers. However, enabling BBR requires a Linux kernel version of 4.10 or later. If you use an earlier version, you need to upgrade your kernel.
This document describes how to manually change the kernel and enable BBR in a Linux CVM instance on CentOS 7.5 as an example.
Directions
Updating the kernel package
1. Run the following command to check the current kernel version.
uname -r
2. Run the following command to update the software package.
yum update -y
3. Run the following command to import the public key of ELRepo.
rpm --import https://www.elrepo.org/RPM-GPG-KEY-elrepo.org
4. Run the following command to install the yum repository of ELRepo.
yum install https://www.elrepo.org/elrepo-release-7.0-4.el7.elrepo.noarch.rpm
Installing a new kernel
1. Run the following command to check the supported kernel package in the ELRepo repository.
yum --disablerepo="*" --enablerepo="elrepo-kernel" list available
2. Run the following command to install the latest mainline stable kernel.
yum --enablerepo=elrepo-kernel install kernel-ml
Modifying the grub configuration
1. Run the following command to open the
/etc/default/grub file.vim /etc/default/grub
2. Press i to switch to the edit mode and change 
GRUB_DEFAULT=saved to GRUB_DEFAULT=0.
3. Click Esc and enter :wq to save and close the file.
4. Run the following command to generate the kernel configuration again.
grub2-mkconfig -o /boot/grub2/grub.cfg
5. Run the following command to restart the server.
reboot
6. Run the following command to check whether the modification is successful.
uname -r
Deleting unnecessary kernels
1. Run the following command to view all kernels.
rpm -qa | grep kernel
2. Run the following command to delete the older kernel.
yum remove kernel-old_kernel_version
For example:
yum remove kernel-3.10.0-957.el7.x86_64
Enabling BBR
1. Run the following command to edit the
/etc/sysctl.conf file.vim /etc/sysctl.conf
2. Press i to switch to the edit mode and enter the following:
net.core.default_qdisc=fqnet.ipv4.tcp_congestion_control=bbr
3. Click Esc and enter :wq to save and close the file.
4. Run the following command to load the kernel parameter settings to the
/etc/sysctl.conf configuration file.sysctl -p
5. Run the following commands to verify whether BBR has been successfully enabled.
sysctl net.ipv4.tcp_congestion_control# The following appears if the configuration succeeds:# net.ipv4.tcp_congestion_control = bbr
sysctl net.ipv4.tcp_available_congestion_control# The following appears if the configuration succeeds:# net.ipv4.tcp_available_congestion_control = reno cubic bbr
6. Run the following commend to check whether the kernel module is loaded.
lsmod | grep bbr
If the following information is returned, BBR has been successfully enabled.
Yes
No
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