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COSFS

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Last updated: 2025-11-13 17:20:18

Overview

COSFS allows you to mount COS buckets to local and work with the COS objects as you do with a local file system. COSFS supports the following features:
Most features of the POSIX file system, such as reading/writing files, operations on directories/links, permission management, and uid/gid management.
Multipart upload of large files.
Data verification with MD5.
Data upload to COS using COS Migration or COSCMD.

Limitations

COSFS is built on S3FS. As disks are required for COSFS' read and write operations, COSFS is only suitable for simple management of mounted files and does not support all features of a local POSIX file system. Note the following limitations when using the COSFS tool:
Randomly writing data or appending data to a file may lead to the re-download/re-upload of the entire file. To avoid this, you can use a CVM in the same region as the bucket to accelerate the upload and download.
When a COS bucket is mounted to multiple clients, you need to coordinate the behaviors of these clients, for example, to prevent the clients from simultaneously writing data to the same file.
Rename operation on a file/folder is not atomic.
For metadata operations such as list directory, COSFS performs unsatisfactorily as it requires remote access to the COS server.
COSFS does not support hard links and is inapplicable to high-concurrency reads/writes.
Mounting and unmounting files cannot be performed on the same mount point at the same time. You can use the cd command to switch to another directory and then mount and unmount the files at the mount point.
Regular disk scanning tasks of the server may cause a high CPU utilization of COSFS, which sends a large number of HEAD and LIST requests, incurring a large amount of request fees. For more information, see FAQs.
Not recommended for use in container scenarios.
We recommend you use the following tools rather than COSFS:
WinFsp + GitHub + Rclone: You can use these tools to mount COS as a local drive. For more information, see Mounting COS to Windows Server as Local Drive.

Operating Environments

It supports mainstream Ubuntu, CentOS, SUSE, and macOS systems, and also supports TencentOS 2.4/2.6/3.1.

Installation Methods

You can install COSFS with an installation package or by compiling the source code.

Method 1: Install with an installation package

Note:
This installation method supports only mainstream Ubuntu and CentOS.

1. Installing Dependencies

Ubuntu
sudo apt install libfuse-dev libcurl4-openssl-dev libxml2-dev libssl-dev -y
CentOS
sudo yum install libxml2-devel libcurl-devel fuse-devel openssl-devel fuse -y

2. Obtaining the COSFS Installation Package from the Following Download URLs

CentOS/Tlinux
Use cat /etc/centos-release to view the CentOS version and select an installation package for the corresponding version:
https://downloads.tencentgoosefs.cn/cosfs/cosfs-1.0.22-centos6-x86_64
https://downloads.tencentgoosefs.cn/cosfs/cosfs-1.0.22-centos7-x86_64
https://downloads.tencentgoosefs.cn/cosfs/cosfs-1.0.22-centos8-x86_64
Ubuntu
Use cat /etc/os-release to view the Ubuntu version and select an installation package for the corresponding version:
https://downloads.tencentgoosefs.cn/cosfs/cosfs-1.0.22-ubuntu14.04-x86_64
https://downloads.tencentgoosefs.cn/cosfs/cosfs-1.0.22-ubuntu16.04-x86_64
https://downloads.tencentgoosefs.cn/cosfs/cosfs-1.0.22-ubuntu18.04-x86_64
https://downloads.tencentgoosefs.cn/cosfs/cosfs-1.0.22-ubuntu20.04-x86_64
https://downloads.tencentgoosefs.cn/cosfs/cosfs-1.0.22-ubuntu22.04-x86_64
For other systems, install COSFS by compiling the source code.
Installation Methods
Replace $download_url below with a download URL for the corresponding OS version.
curl -o cosfs $download_url
chmod +x cosfs
mv cosfs /usr/local/bin/cosfs

Method 2: Install by compiling the source code

Note:
This installation method supports mainstream Ubuntu, CentOS, SUSE, and macOS.

1. Install the dependency software

The compilation and installation of COSFS depend on software packages such as automake, git, libcurl-devel, libxml2-devel, fuse-devel, make, and openssl-devel. The following describes how to install dependency software on Ubuntu, CentOS, SUSE, and macOS:
Install dependency software on the Ubuntu system:
sudo apt-get install automake autotools-dev g++ git libcurl4-gnutls-dev libfuse-dev libssl-dev libxml2-dev make pkg-config fuse
Install dependency software on the CentOS system:
sudo yum install automake gcc-c++ git libcurl-devel libxml2-devel fuse-devel make openssl-devel fuse
Install dependency software on the SUSE system:
sudo zypper install gcc-c++ automake make libcurl-devel libxml2-devel openssl-devel pkg-config
Install dependency software on the macOS system:
brew install automake git curl libxml2 make pkg-config openssl 
brew install cask osxfuse

2. Obtain the source code

Download the COSFS Source Code from GitHub to a specified directory. The following uses /usr/cosfs as an example. You can use another directory as needed.
sudo git clone https://github.com/tencentyun/cosfs /usr/cosfs

3. Compile and install COSFS

Open the installation directory, and execute the following command to compile and install COSFS:
cd /usr/cosfs
sudo ./autogen.sh
sudo ./configure
sudo make
sudo make install
cosfs --version  #View the COSFS version number

4. Troubleshoot configure issues

Messages displayed during the configure operation vary depending on the OS. If your FUSE version is earlier than 2.8.4, the following error message will be displayed:
checking for common_lib_checking... configure: error: Package requirements (fuse >= 2.8.4 libcurl >= 7.0 libxml-2.0 >= 2.6) were not met:
  Requested 'fuse >= 2.8.4' but version of fuse is 2.8.3
In this case, you need to manually install fuse 2.8.4 or later as shown below:
sudo yum -y remove fuse-devel
yum -y remove fuse-devel84%97sudo wget https://github.com/libfuse/libfuse/releases/download/fuse_2_9_4/fuse-2.9.4.tar.gz
tar -zxvf fuse-2.9.4.tar.gz
cd fuse-2.9.4
sudo ./configure
sudo make
sudo make install
export PKG_CONFIG_PATH=/usr/lib/pkgconfig:/usr/lib64/pkgconfig/:/usr/local/lib/pkgconfig
modprobe fuse   # Mount FUSE's kernel module.
echo "/usr/local/lib" >> /etc/ld.so.conf
ldconfig   #Update the dynamic link library
pkg-config --modversion fuse  #View the fuse version number. If "2.9.4" is displayed, fuse 2.9.4 is installed successfully.
Install fuse 2.8.4 or later on the SUSE system manually, as shown below:
Note:
During installation, you need to comment out the content of line 222 in example/fusexmp.c by using /*content*/. Otherwise, an error will be reported when you use Make.
zypper remove fuse libfuse2
yum -y remove fuse-devel84%97sudo wget https://github.com/libfuse/libfuse/releases/download/fuse_2_9_4/fuse-2.9.4.tar.gz
tar -zxvf fuse-2.9.4.tar.gz
cd fuse-2.9.4
sudo ./configure
sudo make 
sudo make install
export PKG_CONFIG_PATH=/usr/lib/pkgconfig:/usr/lib64/pkgconfig/:/usr/local/lib/pkgconfig
modprobe fuse   # Mount FUSE's kernel module.
echo "/usr/local/lib" >> /etc/ld.so.conf
ldconfig   # Update the dynamic-link library.
pkg-config --modversion fuse   #View the fuse version number. If "2.9.4" is displayed, fuse 2.9.4 is installed successfully.
When the "configure" operation is performed on macOS, the following may be displayed:
configure: error: Package requirements (fuse >= 2.7.3 libcurl >= 7.0 libxml-2.0 >2.6 libcrypto >= 0.9) were not met
No package 'libcrypto' found
In this case, you need to set the variable PKG_CONFIG_PATH, so that the pkg-config tool can find openssl. The command is as follows:
brew info openssl 
export PKG_CONFIG_PATH=/usr/local/opt/openssl/lib/pkgconfig #You may need to modify this command based on the message displayed for the previous command.

How to Use

1. Configure the key file

Write the bucket information in the /etc/passwd-cosfs file, including the bucket name (in BucketName-APPID format), <SecretId>, as well as <SecretKey>, and use colons (:) to separate them. To avoid compromising your key, set permissions for the key file to 640. Run the following command to configure the /etc/passwd-cosfs key file:
sudo su  # Switch to the root account to modify the /etc/passwd-cosfs file. Skip this step if you have already logged in with the root account
echo <BucketName-APPID>:<SecretId>:<SecretKey> > /etc/passwd-cosfs
chmod 640 /etc/passwd-cosfs
Note:
You need to replace the content enclosed in <> with the actual information.
<BucketName-APPID> indicates the name of the bucket. For more information, see Bucket Naming Conventions.
<SecretId> and <SecretKey> are key information. We recommend you use a sub-account key and authorize a sub-account by following the Notes on Principle of Least Privilege to reduce risks. For details on how to obtain a sub-account key, see Access Key.
You can configure the key in $HOME/.passwd-cosfs. Alternatively, you can run -opasswd_file=[path] to specify the directory of the key file and then set permissions of the key file to 600.
Example:
echo examplebucket-1250000000:AKIDHTVVaVR6e3****:PdkhT9e2rZCfy6**** > /etc/passwd-cosfs
chmod 640 /etc/passwd-cosfs
Note:
If your COSFS version is v1.0.5 or earlier, the configuration file format is <BucketName>:<SecretId>:<SecretKey>.

2. Run the tool

Run the following command to mount the bucket configured in the key file to a specified directory:
cosfs <BucketName-APPID> <MountPoint> -ourl=http://cos.<Region>.myqcloud.com -odbglevel=info -oallow_other
Parameter description
<MountPoint> is the mount point, for example, /mnt.
<Region>is the abbreviation for the region, such as ap-guangzhou and eu-frankfurt. For more information about region abbreviations, see Regions and Access Endpoints.
-odbglevel specifies the log level. The default value is crit. Available options are crit, error, warn, info, and debug.
-oallow_other allows other users to access the mount folder.
Example:
mkdir -p /mnt/cosfs
cosfs examplebucket-1250000000 /mnt/cosfs -ourl=http://cos.ap-guangzhou.myqcloud.com -odbglevel=info -onoxattr -oallow_other
Note:
To improve performance, COSFS uses the system disk by default for the temporary cache of uploaded and downloaded files and releases space after files are closed. When a large number of concurrent files are opened or large files are read or written, COSFS uses hard disk space as much as possible to improve performance. By default, only 100 MB of free hard disk space is reserved for other applications. You can use the oensure_diskfree=[size] option to set the size of available hard disk space in MB reserved by COSFS. For example, -oensure_diskfree=1024 indicates that COSFS will reserve 1024 MB of free space.
If your COSFS is v1.0.5 or earlier, use the following mount command: cosfs <APPID>:<BucketName> <MountPoint> -ourl=<CosDomainName> -oallow_other.

3. Unmount a bucket

Unmount a bucket using the following commands:
Method 1: Use `fusermount -u /mnt, fusermount` to unmount a FUSE file system 
Method 2: Use `umount -l /mnt`. The unmount operation will be performed when no program is using any file in the file system.
Method 3: Use `umount /mnt`. If any program is using a file in the file system during the unmount, an error will be reported.

Common Mounting Options

-omultipart_size=[size]

Specifies the size (in MB) of each part for the multipart upload. It is 10 MB by default. Up to 10,000 parts are allowed for a file in a multipart upload. If the file is larger than 100 GB (10 MB * 10000), you need to adjust this parameter accordingly.

-oallow_other

Allows other users to access the folder to which the bucket is mounted.

-odel_cache

By default, to ensure optimal performance, the COSFS does not clear local cached data after a bucket is unmounted. To enable the COSFS to automatically clear cached data upon its exit, you can add this option during mounting.

-onoxattr

Disables getattr/setxattr. For the COSFS earlier than 1.0.9, you cannot set or obtain extended attributes. If the use_xattr option is used during mounting, the files may fail to be copied to the bucket.

-opasswd_file=[path]

Specifies the path for the COSFS key file. You need to set the permission for the key file to 600.

-odbglevel=[dbg|info|warn|err|crit]

Sets the log level for COSFS. Valid values: info, dbg, warn, err, crit. You are advised to set it to info in the production environment, and dbg for debugging. If you do not clear system logs regularly, or numerous logs will be generated due to a huge access volume, you can set it to err or crit.

-oumask=[perm]

Removes the permission of a specified type of users to operate files in the mounting destination directory. For example, when -oumask=0222, the permission for the mounting destination directory is changed to 555.
Note:
The umask here should start with 0 to indicate that it is in octal format, ranging from 0 to 0777.

-ouid=[uid]

Allows the user whose ID is [uid] to access all the files in the mounting destination directory without being restricted by the file permission bits. You can obtain the uid of a user using the ID command id -u username. For example, you can run id -u user_00 to obtain the uid of user_00.

-oensure_diskfree=[size]

To improve performance, COSFS uses the system disk by default for the temporary cache of uploaded and downloaded files and releases space after files are closed. When a large number of concurrent files are opened or large files are read or written, COSFS uses hard disk space as much as possible to improve performance. By default, only 100 MB of free hard disk space is reserved for other applications. You can use the oensure_diskfree=[size] option to set the size of available hard disk space in MB reserved by COSFS. For example, -oensure_diskfree=1024 indicates that COSFS will reserve 1024 MB of free space.

FAQs

Some FAQs about COSFS are listed below. If you have more questions, see COSFS FAQs.
What should I do if COSFS has a high CPU utilization, sends a large number of HEAD and LIST requests to COS, and incurs a large amount of request fees during a certain period of time every day?
Why does it take the ls command so long to return when I run it in a COSFS directory?
Next Topic: Release Notes

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