Symbolic links are a convenient way to access frequently used objects in a bucket. After creation, you can use a symbolic link like a Windows shortcut to access the target object.
Usage notes
-
You can directly access Standard or Infrequent Access objects through their symbolic links.
-
To access an Archive, Cold Archive, or Deep Cold Archive object through a symbolic link, you must first restore the object. For more information, see Restore objects.
-
A symbolic link stores the path of a target object, not its content. Therefore, a symbolic link's storage usage depends on the length of the target object's path, not the actual size of the target object. For example, for a symbolic link that points to a 1 MB object named image.jpg, the symbolic link itself uses only about 0.009 KB of storage.
-
Access to a symbolic link follows the principle of least privilege. In scenarios that involve a bucket policy or a RAM policy, a user must have permissions to access both the symbolic link and its target object. Access is denied if either permission is missing. For scenarios that involve an access control list (ACL), if a symbolic link is private, a user cannot use it to access the target object even if the target object is public-read. Likewise, if a symbolic link is public-read but the target object is private, access is also denied.
-
Symbolic links do not support server-side encryption.
Procedure
OSS console
-
Log on to the OSS console.
-
In the left-side navigation pane, click Buckets. On the page that appears, click the name of the target bucket.
-
In the left navigation bar, select Object Management
Objects.
-
In the Actions column for the target object, choose
> Configure Symbolic Link. -
In the Configure Symbolic Link panel, set Symbolic Link File or Folder, and then click OK.
The name that you specify for the symbolic link must follow the naming conventions displayed in the console. Assume that the current object is in the /test/ directory:
-
If you select Absolute Path and name the symbolic link t1-symlink, the path of the symbolic link is
/t1-symlink. -
If you select Relative Path and name the symbolic link t2-symlink, the path of the symbolic link is
/test/t2-symlink.
ImportantIf the filename of a symbolic link does not include a file extension (for example, the symbolic link for the object myphoto.jpg is named myphoto), you can still preview the symbolic link by accessing it from the console or a URL. When you download the symbolic link by using a tool or the console, the downloaded file is considered a file of an unknown type and cannot be opened directly because it does not have a file extension. To open the file, add the correct file extension.
-
ossbrowser
Ensure that you have installed ossbrowser 2.0 and logged on to it.
-
Click the name of the target bucket and find the target object.
-
Click the
icon to the right of the target object, and then click Configure Symbolic Link. -
Enter the full path for the symbolic link, including the file name, and then click OK. For example, to create a symbolic link named symlink in the exampledir/ directory for the target object, enter exampledir/symlink.
Alibaba Cloud SDKs
The following code shows how to create a symbolic link by using Alibaba Cloud SDKs for popular programming languages. For information about using SDKs for other languages, see SDK overview.
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;
}ossutil
You can use ossutil to create symbolic links. For more information about how 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 targetobject
For more information about this command, see put-symlink.
API reference
For advanced customization, you can make direct REST API requests. This requires you to manually calculate a signature in your code. For more information, see PutSymlink.
FAQ
Can I create a symbolic link for a private object?
Creating a symbolic link is independent of the target object's read and write permissions. You can create symbolic links for objects with any access control list (ACL) setting, including bucket-owner-full-control, private, public-read, and public-read-write.
How do I determine whether an object is a symbolic link?
You can call the HeadObject or GetObject operation and check 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 headers in the response are the metadata of the target object.
If I delete a symbolic link, is the target object also deleted?
No. Deleting a symbolic link removes only the link itself and does not affect the target object.