Symbolic links provide easy access to frequently used objects in a bucket. After you create a symbolic link, you can use it to access the target object, similar to a shortcut in Windows.
Notes
You can access Standard and Infrequent Access objects using their symbolic links.
To access Archive Storage, Cold Archive, or Deep Cold Archive objects using a symbolic link, you must first restore the object. For more information, see Restore objects.
A symbolic link stores the path of the target object, not its content. Therefore, the storage space that a symbolic link uses depends on the length of the target object's path, not the actual size of the object. For example, a symbolic link that points to a 1 MB object named image.jpg uses about 0.009 KB of storage.
Access permissions for symbolic links follow the principle of least privilege. In scenarios that use a bucket policy or a RAM policy for authorization, a user must have permissions to access both the symbolic link and the target object to access the object using the link. If the user does not have permission to access the symbolic link or the target object, the access request is denied. In scenarios that use access control lists (ACLs), if a symbolic link is private, a user cannot access the target object using the link, even if the target object is public-read. Likewise, if a symbolic link is public-read but the target object is private, the user cannot access the target object.
Symbolic links do not support server-side encryption.
Methods
Use the OSS console
Log on to the OSS console.
In the left-side navigation pane, click Buckets. On the Buckets page, find and click the desired bucket.
In the left navigation pane, choose Object Management
Objects
In the Actions column of the target object, click
> Configure Symbolic Link.In the Configure Symbolic Link panel, set Symbolic Link File or Folder and click OK.
When you specify the symbolic link path, follow the naming conventions that appear on the screen. For example, if the target object is in the `/test/` folder:
If you select Absolute Path and name the link t1-symlink, the path of the symbolic link is
/t1-symlink.If you select Relative Path and name the link t2-symlink, the path of the symbolic link is
/test/t2-symlink.
ImportantIf a symbolic link does not have a file name extension, such as a link named myphoto for the object myphoto.jpg, you can still preview the object by accessing the link from the console or a URL. However, if you download the symbolic link, the downloaded file will be of an unknown type and cannot be opened directly. To open the file, you must add the correct file name extension.
Use the ossbrowser graphical tool
Make sure that you have installed ossbrowser 2.0 and logged on to ossbrowser 2.0.
Click the name of the target bucket and find the target object.
Click
next to the target object, and then click Create Symbolic Link.Enter the full path of the symbolic link, including the file name, and click OK. For example, to create a symbolic link named `symlink` in the `exampledir` folder, enter `exampledir/symlink`.
Use Alibaba Cloud SDKs
The following code provides examples of how to create a symbolic link using common SDKs. For more information about how to create a symbolic link using other SDKs, see Introduction to SDKs.
import com.aliyun.oss.*;
import com.aliyun.oss.common.auth.*;
import com.aliyun.oss.common.comm.SignVersion;
import com.aliyun.oss.model.*;
public class Demo {
public static void main(String[] args) throws Exception {
// In this example, the endpoint of the China (Hangzhou) region is used. Specify your actual endpoint.
String endpoint = "https://oss-cn-hangzhou.aliyuncs.com";
// Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured.
EnvironmentVariableCredentialsProvider credentialsProvider = CredentialsProviderFactory.newEnvironmentVariableCredentialsProvider();
// Specify the name of the bucket. Example: examplebucket.
String bucketName = "examplebucket";
// Specify the name of the symbolic link that you want to create.
String symLink = "yourSymLink";
// Specify the name of the object to which you want the symbolic link to point.
String destinationObjectName = "yourDestinationObjectName";
// Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou.
String region = "cn-hangzhou";
// Create an OSSClient instance.
// Call the shutdown method to release resources when the OSSClient is no longer in use.
ClientBuilderConfiguration clientBuilderConfiguration = new ClientBuilderConfiguration();
clientBuilderConfiguration.setSignatureVersion(SignVersion.V4);
OSS ossClient = OSSClientBuilder.create()
.endpoint(endpoint)
.credentialsProvider(credentialsProvider)
.clientConfiguration(clientBuilderConfiguration)
.region(region)
.build();
try {
// Create metadata for the object that you want to upload.
ObjectMetadata metadata = new ObjectMetadata();
metadata.setContentType("text/plain");
// Set the property parameter for the user metadata to property-value.
metadata.addUserMetadata("property", "property-value");
// Specify whether to overwrite the object that has the same name as the symbolic link.
// metadata.setHeader("x-oss-forbid-overwrite", "true");
// Specify the access control list (ACL) of the object.
// metadata.setHeader(OSSHeaders.OSS_OBJECT_ACL, CannedAccessControlList.Default);
// Specify the storage class of the object.
// metadata.setHeader(OSSHeaders.OSS_STORAGE_CLASS, StorageClass.Standard);
// Create a CreateSymlinkRequest to create the symbolic link.
CreateSymlinkRequest createSymlinkRequest = new CreateSymlinkRequest(bucketName, symLink, destinationObjectName);
// Configure the metadata.
createSymlinkRequest.setMetadata(metadata);
// Create the symbolic link.
ossClient.createSymlink(createSymlinkRequest);
} catch (OSSException oe) {
System.out.println("Caught an OSSException, which means your request made it to OSS, "
+ "but was rejected with an error response for some reason.");
System.out.println("Error Message:" + oe.getErrorMessage());
System.out.println("Error Code:" + oe.getErrorCode());
System.out.println("Request ID:" + oe.getRequestId());
System.out.println("Host ID:" + oe.getHostId());
} catch (ClientException ce) {
System.out.println("Caught an ClientException, which means the client encountered "
+ "a serious internal problem while trying to communicate with OSS, "
+ "such as not being able to access the network.");
System.out.println("Error Message:" + ce.getMessage());
} finally {
if (ossClient != null) {
ossClient.shutdown();
}
}
}
} const OSS = require('ali-oss')
const client = new OSS({
// Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to oss-cn-hangzhou.
region: 'yourRegion',
// Obtain access credentials from environment variables. Before you run the sample code, make sure that you have configured environment variables OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET.
accessKeyId: process.env.OSS_ACCESS_KEY_ID,
accessKeySecret: process.env.OSS_ACCESS_KEY_SECRET,
authorizationV4: true,
// Specify the name of the bucket.
bucket: 'examplebucket',
});
const headers = {
// Specify the storage class of the object.
'x-oss-storage-class':'Standard',
// Specify the access control list (ACL) of the object.
'x-oss-object-acl':'private',
// Specify whether to overwrite the object that has the same name as the symbolic link. In this example, this parameter is set to true, which indicates that the object with the same name cannot be overwritten.
'x-oss-forbid-overwrite': 'true '
};
async function put () {
try {
// Specify symlinkobject.txt as the name of the symbolic link and exampleobject.txt as the name of the object to which you want the symbolic link to point.
const result = await client.putSymlink('symlinkobject.txt', 'exampleobject.txt'
// ,{ headers }
);
console.log(result);
} catch (e) {
console.log(e);
}
}
put();<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>Document</title>
</head>
<body>
<button id='upload'>Upload</button>
<button id='symlink'>Create Symbolic Link</button>
<!-- Import the SDK file -->
<script type="text/javascript" src="https://gosspublic.alicdn.com/aliyun-oss-sdk-6.18.0.min.js"></script>
<script type="text/javascript">
const client = new OSS({
// Specify the region in which the bucket is located. For example, if your bucket is located in the China (Hangzhou) region, set the region to oss-cn-hangzhou.
region: 'yourRegion',
authorizationV4: true,
// Specify the temporary AccessKey pair obtained from STS. The AccessKey pair consists of an AccessKey ID and an AccessKey secret.
accessKeyId: 'yourAccessKeyId',
accessKeySecret: 'yourAccessKeySecret',
// Specify the security token obtained from STS.
stsToken: 'yourSecurityToken',
// Specify the name of the bucket. Example: examplebucket.
bucket: "examplebucket",
});
const upload = document.getElementById('upload')
const symlink = document.getElementById('symlink')
const getSymlink = document.getElementById("getSymlink")
// Specify the content of the object to upload.
const file = new Blob(['examplecontent'])
// Specify the name of the object to upload to the bucket.
const fileName = 'exampleobject.txt'
// Upload the object.
upload.addEventListener('click', () => {
client.put(fileName, file).then(r => console.log(r))
})
// Create a symbolic link named symlink.txt.
symlink.addEventListener('click', () => {
client.putSymlink('symlink.txt', fileName).then(r => console.log(r))
})
</script>
</body>
</html>using Aliyun.OSS;
using System.Text;
using Aliyun.OSS.Common;
// Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com.
var endpoint = "yourEndpoint";
// Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured.
var accessKeyId = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_ID");
var accessKeySecret = Environment.GetEnvironmentVariable("OSS_ACCESS_KEY_SECRET");
// Specify the name of the bucket. Example: examplebucket.
var bucketName = "examplebucket";
var targetObjectName = "yourTargetObjectName";
var symlinkObjectName = "yourSymlinkObjectName";
var objectContent = "More than just cloud.";
// Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou.
const string region = "cn-hangzhou";
// Create a ClientConfiguration instance and modify the default parameters based on your requirements.
var conf = new ClientConfiguration();
// Use the signature algorithm V4.
conf.SignatureVersion = SignatureVersion.V4;
// Create an OSSClient instance.
var client = new OssClient(endpoint, accessKeyId, accessKeySecret, conf);
client.SetRegion(region);
try
{
// Upload the object to which the symbolic link points.
byte[] binaryData = Encoding.ASCII.GetBytes(objectContent);
MemoryStream requestContent = new MemoryStream(binaryData);
client.PutObject(bucketName, targetObjectName, requestContent);
// Create the symbolic link.
client.CreateSymlink(bucketName, symlinkObjectName, targetObjectName);
// Query the name of the object to which the symbolic link points.
var ossSymlink = client.GetSymlink(bucketName, symlinkObjectName);
Console.WriteLine("Target object is {0}", ossSymlink.Target);
}
catch (Exception ex)
{
Console.WriteLine("Failed with error info: {0}", ex.Message);
}// Create a request.
PutSymlinkRequest putSymlink = new PutSymlinkRequest();
// Specify the name of the bucket.
putSymlink.setBucketName("yourBucketName");
// Specify the name of the symbolic link.
putSymlink.setObjectKey("yourSymLink");
// Specify the name of the object to which you want the symbolic link to point.
putSymlink.setTargetObjectName("yourTargetObjectName");
ObjectMetadata metadata = new ObjectMetadata();
// Specify whether to overwrite the object that has the same name. In this example, this parameter is set to true, which indicates that the object that has the same name cannot be overwritten.
//metadata.setHeader("x-oss-forbid-overwrite", "true");
// Specify the access control list (ACL) of the object. In this example, the ACL is set to private.
//metadata.setHeader("x-oss-object-acl", "private");
// Specify the storage class of the object. In this example, the storage class is set to Standard.
//metadata.setHeader("x-oss-storage-class", "Standard");
putSymlink.setMetadata(metadata);
OSSAsyncTask task = oss.asyncPutSymlink(putSymlink, new OSSCompletedCallback<PutSymlinkRequest, PutSymlinkResult>() {
@Override
public void onSuccess(PutSymlinkRequest request, PutSymlinkResult result) {
Log.d("PutSymlink", "PutSymlink success");
}
@Override
public void onFailure(PutSymlinkRequest request, ClientException clientException,
ServiceException serviceException) {
// Handle request exceptions.
if (clientException != null) {
// Handle client exceptions, such as network exceptions.
clientException.printStackTrace();
}
if (serviceException != null) {
// Handle server-side exceptions.
Log.e("ErrorCode", serviceException.getErrorCode());
Log.e("RequestId", serviceException.getRequestId());
Log.e("HostId", serviceException.getHostId());
Log.e("RawMessage", serviceException.getRawMessage());
}
}
});
task.waitUntilFinished();OSSPutSymlinkRequest *request = [OSSPutSymlinkRequest new];
// Specify the name of the bucket. Example: examplebucket.
request.bucketName = @"examplebucket";
// Specify the name of the symbolic link.
request.objectKey = @"examplesymlink";
// Specify the full path of the object to which you want the symbolic link to point. Do not include the bucket name in the full path.
request.targetObjectName = @"exampleobject.txt";
OSSTask *putSymlinkTask = [client putSymlink:request];
[putSymlinkTask continueWithBlock:^id _Nullable(OSSTask * _Nonnull task) {
if (!task.error) {
NSLog(@"put symlink success");
} else {
NSLog(@"put symlink failed, error: %@", task.error);
}
return nil;
}];
// Implement synchronous blocking to wait for the task to complete.
// [putSymlinkTask waitUntilFinished];#include <alibabacloud/oss/OssClient.h>
using namespace AlibabaCloud::OSS;
int main(void)
{
/* Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
std::string Endpoint = "yourEndpoint";
/* Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou. */
std::string Region = "yourRegion";
/* Specify the name of the bucket. Example: examplebucket. */
std::string BucketName = "examplebucket";
/* Specify the full path of the object. Example: exampledir/exampleobject.txt. Do not include the bucket name in the full path. */
std::string ObjectName = "exampledir/exampleobject.txt";
/* Specify the full path of the symbolic link. Example: shortcut/myobject.txt. */
std::string LinkName = "shortcut/myobject.txt";
/* Initialize resources, such as network resources. */
InitializeSdk();
ClientConfiguration conf;
conf.signatureVersion = SignatureVersionType::V4;
/* Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. */
auto credentialsProvider = std::make_shared<EnvironmentVariableCredentialsProvider>();
OssClient client(Endpoint, credentialsProvider, conf);
client.SetRegion(Region);
/* Configure the HTTP headers. */
auto meta = ObjectMetaData();
meta.setContentType("text/plain");
/* Configure the user metadata of the object. */
meta.UserMetaData()["meta"] = "meta-value";
/* Create the symbolic link. */
CreateSymlinkRequest request(BucketName, ObjectName, meta);
request.SetSymlinkTarget(LinkName);
auto outcome = client.CreateSymlink(request);
if (!outcome.isSuccess()) {
/* Handle exceptions. */
std::cout << "CreateSymlink fail" <<
",code:" << outcome.error().Code() <<
",message:" << outcome.error().Message() <<
",requestId:" << outcome.error().RequestId() << std::endl;
return -1;
}
/* Release resources, such as network resources. */
ShutdownSdk();
return 0;
}#include "oss_api.h"
#include "aos_http_io.h"
/* Specify the endpoint of the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the endpoint to https://oss-cn-hangzhou.aliyuncs.com. */
const char *endpoint = "yourEndpoint";
/* Specify the name of the bucket. Example: examplebucket. */
const char *bucket_name = "examplebucket";
/* Specify the full path of the object. Do not include the bucket name in the full path. Example: exampledir/exampleobject.txt. */
const char *object_name = "exampledir/exampleobject.txt";
/* Specify the full path of the symbolic link that you want to create. */
const char *link_object_name = "yourLinkObjectName";
/* Specify the region in which the bucket is located. For example, if the bucket is located in the China (Hangzhou) region, set the region to cn-hangzhou. */
const char *region = "yourRegion";
void init_options(oss_request_options_t *options)
{
options->config = oss_config_create(options->pool);
/* Use a char* string to initialize data of the aos_string_t type. */
aos_str_set(&options->config->endpoint, endpoint);
/* Obtain access credentials from environment variables. Before you run the sample code, make sure that the OSS_ACCESS_KEY_ID and OSS_ACCESS_KEY_SECRET environment variables are configured. */
aos_str_set(&options->config->access_key_id, getenv("OSS_ACCESS_KEY_ID"));
aos_str_set(&options->config->access_key_secret, getenv("OSS_ACCESS_KEY_SECRET"));
// Specify two additional parameters.
aos_str_set(&options->config->region, region);
options->config->signature_version = 4;
/* Specify whether to use CNAME. The value 0 indicates that CNAME is not used. */
options->config->is_cname = 0;
/* Specify network parameters, such as the timeout period. */
options->ctl = aos_http_controller_create(options->pool, 0);
}
int main(int argc, char *argv[])
{
/* Call the aos_http_io_initialize method in main() to initialize global resources, such as network resources and memory resources. */
if (aos_http_io_initialize(NULL, 0) != AOSE_OK) {
exit(1);
}
/* Create a memory pool to manage memory. aos_pool_t is equivalent to apr_pool_t. The code used to create a memory pool is included in the APR library. */
aos_pool_t *pool;
/* Create a memory pool. The value of the second parameter is NULL. This value indicates that the pool does not inherit other memory pools. */
aos_pool_create(&pool, NULL);
/* Create and initialize options. This parameter includes global configuration information, such as endpoint, access_key_id, access_key_secret, is_cname, and curl. */
oss_request_options_t *oss_client_options;
/* Allocate the memory resources in the memory pool to the options. */
oss_client_options = oss_request_options_create(pool);
/* Initialize oss_client_options. */
init_options(oss_client_options);
/* Initialize the parameters. */
aos_string_t bucket;
aos_string_t object;
aos_string_t sym_object;
aos_table_t *resp_headers = NULL;
aos_status_t *resp_status = NULL;
aos_str_set(&bucket, bucket_name);
aos_str_set(&object, object_name);
aos_str_set(&sym_object, link_object_name);
resp_status = oss_put_symlink(oss_client_options, &bucket, &sym_object, &object, &resp_headers);
if (aos_status_is_ok(resp_status)) {
printf("put symlink succeeded\n");
} else {
printf("put symlink failed\n");
}
/* Release the memory pool. This operation releases the memory resources allocated for the request. */
aos_pool_destroy(pool);
/* Release the allocated global resources. */
aos_http_io_deinitialize();
return 0;
}Use the ossutil command-line tool
You can use the ossutil command-line tool to create symbolic links. To install ossutil, see Install ossutil.
The following command creates a symbolic link named examplelink that points to the target object targetobject.
ossutil api put-symlink --bucket examplebucket --key examplelink --symlink-target targetobjectFor more information about this command, see put-symlink.
Related API operations
The preceding methods are based on API operations. If your program requires a high degree of customization, you can directly call API operations by sending REST API requests. If you choose to do this, you must manually write code to calculate the required signatures. For more information, see PutSymlink.
FAQ
Can I create a symbolic link for a private object?
Yes, you can. The ability to create a symbolic link is independent of the object's ACL. You can create symbolic links for objects with ACLs set to Inherit from Bucket, Private, public-read, or Public Read/Write.
How do I determine whether an object is a symbolic link?
You can determine whether an object is a symbolic link by calling the HeadObject or GetObject operation and inspecting the response.
If the object is a symbolic link, the response contains the content of the target object. The Content-Length, ETag, and Content-Md5 response headers contain the metadata of the target object.
Does deleting a symbolic link in OSS also delete the source object?
No, it does not. Deleting a symbolic link affects only the link itself and does not delete the target object.