Object Storage Service:FAQ about ossfs

Introduction

An ossfs error includes a message that can help you identify and resolve issues. For example, you can enable the debug logging feature to resolve socket connection failures or errors with HTTP status codes 4xx or 5xx.

• Errors with HTTP status code 403 occur when access is denied due to a lack of the required access permissions.

• Errors with HTTP status code 400 occur due to incorrect requests.

• Errors with HTTP status code 5xx occur due to network jitters and server errors.

ossfs provides the following features:

• ossfs mounts remote Object Storage Service (OSS) buckets to local disks. We recommend that you do not use ossfs to manage business applications that require high read and write performance.

• ossfs operations are not atomic, which means that an operation may succeed locally but fail remotely on OSS.

If ossfs cannot meet your business requirements, you can use ossutil.

What do I do if the "conflicts with file from package fuse-devel" error is reported when I use yum/apt-get to install ossfs?

Analysis: This error occurs because an earlier version of fuse exists in the system and conflicts with the dependency version of ossfs.

Solution: Use a package manager to uninstall fuse and reinstall ossfs.

What do I do if the "fuse: warning: library too old, some operations may not work" error is reported when I install ossfs?

Analysis: This error usually occurs because you manually installed libfuse, and the libfuse version used for ossfs compiling is later than the version that is linked to ossfs during runtime. The ossfs installation package provided by Alibaba Cloud contains libfuse 2.8.4. When you install ossfs in CentOS 5.x or CentOS 6.x, this error occurs if libfuse 2.8.3 already exists in the system and is linked to ossfs.

You can run the ldd $(which ossfs) | grep fuse command to check the fuse version that is linked to ossfs during runtime. If /lib64/libfuse.so.2 is returned in the command output, you can run the ls -l /lib64/libfuse* command to check the fuse version.

What do I do if the error shown in the following figure is reported when I install fuse?

Analysis: This error occurs because the version of fuse does not meet the requirements of ossfs.

Solution: Download and install the latest version of fuse. Do not use yum to install fuse. For more information, visit libfuse.

What do I do if the "ossfs: unable to access MOUNTPOINT /tmp/ossfs: Transport endpoint is not connected" error is reported when I use ossfs to mount a bucket?

Analysis: This error occurs because the destination directory of the OSS bucket is not created.

Solution: Create the destination directory and then mount the bucket.

What do I do if the "fusermount: failed to open current directory: Permission denied" error is reported when I use ossfs to mount a bucket?

Analysis: This error occurs due to a bug in fuse that requires you to have the read permissions on the current directory instead of the destination directory of the OSS bucket.

Solution: Run the cd command to switch to a directory on which you have the read permissions, and use ossfs to mount the bucket.

What do I do if the "ossfs: Mountpoint directory /tmp/ossfs is not empty. if you are sure this is safe, can use the 'nonempty' mount option" error is reported when I use ossfs to mount a bucket?

Analysis: By default, ossfs can mount an OSS bucket only to an empty directory. This error occurs when ossfs attempts to mount a bucket to a directory that is not empty.

Solution: Switch to an empty directory and re-mount the bucket. If you still want the bucket to be mounted to the current directory, use the -ononempty option.

What do I do if the "ops-nginx-12-32 s3fs[163588]: [tid-75593]curl.cpp:CurlProgress(532): timeout now: 1656407871, curl_times[curl]: 1656407810, readwrite_timeout: 60" error is reported when I mount a bucket?

Analysis: The mount operation timed out.

Solution: ossfs uses the readwrite_timeout option to specify the timeout period for read or write requests. Unit: seconds. Default value: 60. You must increase the value of this option based on your business scenarios.

What do I do if the "ossfs: credentials file /etc/passwd-ossfs should not have others permissions" error is reported when I mount a bucket?

Analysis: The permissions on the /etc/passwd-ossfs file are incorrectly configured.

Solution: The /etc/passwd-ossfs file contains access credentials. You need to prevent other users from accessing the file. To resolve this issue, modify the permissions on the file by running the chmod 640 /etc/passwd-ossfs command.

What do I do if the "operation not permitted" error is reported when I run the ls command to list objects in a directory after I mount a bucket?

Analysis: The file system has strict limits on object and directory names. This error occurs when the names of objects in the bucket contain invisible characters.

Solution: Rename the objects appropriately and then run the ls command. The objects in the directory are displayed.

What do I do if the "Operation not permitted" error is reported when I run the rm command to delete an object?

Analysis: When you use the rm command to delete an object, the DeleteObject operation is called to delete the object. If you mount a bucket by using a RAM user, check whether the RAM user has the permissions to delete the object.

Solution: Grant the RAM user the required permissions to delete objects. For more information, see RAM policies and Common examples of RAM policies.

How do I resolve occasional disconnections from ossfs?

What do I do if the "The bucket you are attempting to access must be addressed using the specified endpoint" error is reported when I access a bucket?

Solution: Check whether the configurations are correct and modify the configurations if necessary.

What do I do if the "input/output error" error is reported when I run the cp command to copy data?

Analysis: This error occurs when system disk errors are captured. You can check whether heavy read and write loads exist on the disk.

Solution: Specify multipart parameters to manage the read and write operations on objects. You can run the ossfs -h command to view the multipart parameters.

What do I do if the "input/output error" error is reported when I use rsync for data synchronization?

Analysis: This error occurs when ossfs is used with rsync. In this example, the cp command is run to copy a large object that is 141 GB in size. This causes heavy read and write loads on the disk.

Solution: Use ossutil to download OSS objects to a local Elastic Compute Service (ECS) instance or upload objects from a local device to an ECS instance by performing multipart upload.

What do I do if the "There is no enough disk space for used as cache(or temporary)" error is reported when I use ossfs to upload a large object to OSS?

• Cause:

  The available disk space is less than the size that is specified by multiplying the values of multipart_size and parallel_count.

  multipart_size indicates the part size (default unit: MB). parallel_count indicates the number of parts that you want to upload in parallel (default value: 5).

• Analysis:

  By default, ossfs uploads large objects by performing multipart upload. During the upload, ossfs writes the temporary cache file to the /tmp directory. Before ossfs writes the temporary cache file, it checks whether the available space of the disk where the /tmp directory is located is less than the size specified by multiplying the values of multipart_size and parallel_count. If the available space of the disk is greater than the size specified by multiplying the values of multipart_size and parallel_count, the temporary cache file is written as expected. If the available disk space is less than the size specified by multiplying the values of multipart_size and parallel_count, the system reports that the available disk space is insufficient.

  For example, the available space of the disk is 300 GB and the size of the object that you want to upload is 200 GB, but multipart_size is set to 100000 MB (100 GB) and the number of parts that you want to upload in parallel is set to 5 (default value). In this case, ossfs determines that the size of the object that you want to upload is 500 GB (100 GB × 5). The size is greater than the available space of the disk.

• Solution:

  If the number of parts that you want to upload in parallel remains at the default value of 5, specify a valid value for multipart_size:

  • For example, if the available space of the disk is 300 GB and the size of the object that you want to upload is 200 GB, set multipart_size to 20.

  • For example, if the available space of the disk is 300 GB and the size of the object that you want to upload is 500 GB, set multipart_size to 50.

What do I do if the HTTP status code 403 is returned when I run the touch command on an object in a mounted bucket?

What do I do if the value of the Content-Type parameter of the objects that are uploaded to OSS by using ossfs is application/octet-stream?

Analysis: When you upload an object, ossfs queries the /etc/mime.types file to specify the Content-Type parameter for the object. If the /etc/mime.types file does not exist, the Content-Type parameter is set to application/octet-stream.

Why does the ls command run very slowly when the directory contains a large number of objects?

Analysis: If a directory contains N objects, OSS HTTP requests must be initiated N times for running the ls command to list the N objects in the directory. This can cause serious performance issues when the number of objects is large.

Solution: Increase the stat cache size by specifying the -omax_stat_cache_size parameter. This way, the first run of the ls command is slow, but subsequent runs of the command are fast because metadata is stored in the local cache. For versions earlier than ossfs 1.91.1, the default value of this parameter is 1000. For ossfs 1.91.1 and later, the default value of this parameter is 10000. The metadata of 10,000 objects consumes approximately dozens of MB of memory. You can change the value based on the memory size of your machine.

Why is the object information such as the size of an object displayed by using ossfs different from that displayed by using other tools?

Analysis: By default, ossfs caches object metadata, such as the size and access control list (ACL). Metadata caching accelerates object access by eliminating the need to send requests to OSS every time the Is command is run. However, if the user modifies the object metadata by using tools such as OSS SDKs, the OSS console, or ossutil, the changes are not synchronized to ossfs due to metadata caching. As a result, the metadata that is displayed by using ossfs is different from the metadata that is displayed by using other tools.

Solution: Set the -omax_stat_cache_size parameter to 0 to disable the metadata caching feature. In this case, when the ls command is run, a request is sent to OSS to obtain the latest object metadata each time.

Why does ossfs recognize a directory as a regular object?

• Scenario 1:

  Analysis: If you set content-type to text/plain when you create a directory, which is an object whose name ends with /, ossfs recognizes the object as a regular object.

  Solution: Specify the -ocomplement_stat parameter when you perform the mount operation. If the size of the object is zero bytes or one byte, ossfs recognizes it as a directory.

• Scenario 2:

  Analysis: If you run the ossutil stat directory name (ending with '/') command, such as ossutil stat folder/), you can view the Content-Length field of the object, which is the size of the object. If the size of the object is not zero bytes, ossfs recognizes it as an object.

  Solution: If you no longer need the directory, you can use ossutil to delete it (the objects in the directory are not deleted), or use ossutil to upload an object that has the same name and whose size is zero bytes to overwrite the directory.

What do I do to prevent unnecessary charges due to object scanning by background programs?

Analysis: When background programs scan a directory to which ossfs mounted a bucket, a request is sent to OSS. If a large number of requests are sent, you are charged for the requests.

What do I do if ossfs fails to perform the mv operation on an object?

Cause: The source object may be in one of the following storage classes: Archive, Cold Archive, and Deep Cold Archive.

Solution: Before you perform the mv operation on an Archive, Cold Archive, or Deep Cold Archive object, restore the object first. For more information, see Restore objects.

Why does ossfs require a long period of time to mount a versioning-enabled bucket?

Cause: By default, ossfs lists objects by calling the ListObjects (GetBucket) operation. If versioning is enabled for a bucket, and the bucket contains one or more previous versions of objects and a large number of expired delete markers, the response speed decreases when you call the ListObjects (GetBucket) operation to list current object versions. In this case, ossfs requires a long period of time to mount a versioning-enabled bucket.

Solution: Use the -olistobjectsV2 option to allow ossfs to call the ListObjectsV2(GetBucketV2) operation which has better object listing performance.

How do I mount a bucket over HTTPS by using ossfs?

You can use ossfs to mount a bucket over HTTPS. In this example, the China (Hangzhou) region is used. You can run the following command to mount a bucket over HTTPS:

ossfs examplebucket /tmp/ossfs -o url=https://oss-cn-hangzhou.aliyuncs.com

Why does ossfs occupy the entire storage capacity of a disk?

Cause: To improve performance, ossfs uses the disk to save temporary data that is uploaded or downloaded by default. In this case, the storage capacity of the disk may be exhausted.

Solution: Use the -oensure_diskfree option to specify a reserved storage capacity for the disk. For example, if you want to specify a reserved storage capacity of 20 GB, run the following command:

ossfs examplebucket /tmp/ossfs -o url=http://oss-cn-hangzhou.aliyuncs.com -oensure_diskfree=20480

Why does the storage capacity of a disk change to 256 TB when the df command is run after ossfs mounts a bucket?

The storage capacity of a disk that is displayed when the df command is run does not indicate the actual storage capacity of the OSS bucket. Size (the total storage capacity of a disk) and Avail (the available storage capacity of a disk) are fixed at 256 TB, and Used (the used storage capacity of a disk) is fixed at 0 TB.

The storage capacity of an OSS bucket is unlimited. The used storage capacity varies based on your actual storage usage. For more information about bucket usage, see View the resource usage of a bucket.

Can I mount a bucket on Windows by using ossfs?

No, you cannot mount a bucket on Windows by using ossfs. You can use Rclone to mount a bucket on Windows. For more information, see Mount OSS buckets to local file systems by using Amazon S3 protocols.

What do I do if the "fusermount: failed to unmount /mnt/ossfs-bucket: Device or resource busy" error is reported?

Analysis: A process is accessing objects in the /mnt/ossfs-bucket directory. As a result, the bucket cannot be unmounted.

Solution:

1. Use lsof /mnt/ossfs-bucket to find the process that is accessing the directory.

2. Run the kill command to stop the process.

3. Use fusermount -u /mnt/ossfs-bucket to unmount the bucket.

What do I do if the "fuse: device not found, try 'modprobe fuse'" error is reported?

Analysis: When you use ossfs to perform a mount operation in Docker, the "fuse: device not found, try 'modprobe fuse'" error occurs commonly because the Docker container does not have required access permissions or the permissions to load the fuse kernel module.

Solution: When you use ossfs in a Docker container, specify the --privileged=true parameter to run the Docker container in privileged mode, so that processes in the container have capabilities that the host has, such as using the FUSE file system. The following sample command provides an example on how to run a Docker container with the --privileged flag:

docker run --privileged=true -d your_image

What do I do if the "input/output error" error is reported when I run the Is command to list objects?

Cause: This error mainly occurs in CentOS, with NSS error -8023 in the error log. A communication problem occurs when ossfs uses libcurl to communicate over HTTPS. The communication problem may be because the version of the Network Security Services (NSS) library set that libcurl relies on does not meet the minimum requirements.

Solution: Run the following command to upgrade the NSS library set:

yum update nss