Troubleshooting CURL Exit Code 18 on Amazon Linux 2: SFTP Byte Remaining Issues
In this article, we will discuss a peculiar issue that arises when using CURL on an Amazon Linux 2 server, which results in a failure with exit code 18 and the transfer of only around 1 MB of data. We will troubleshoot this issue and set up a local SFTP server to overcome it. This article will cover key concepts, subtitles, and paragraphs using HTML tags, code blocks, and references.
Understanding the Issue
CURL is a popular command-line tool for transferring data between a client and a server. However, when using CURL to transfer data from an Amazon Linux 2 server, you might encounter a strange issue where the transfer fails with exit code 18, and only around 1 MB of data is transferred. This issue is related to SFTP byte remaining issues.
Troubleshooting the Issue
To troubleshoot this issue, we need to understand the root cause of the problem. The issue is related to the way Amazon Linux 2 handles SFTP connections. When using SFTP, the server sends the client the amount of data that is remaining to be transferred. However, in some cases, the server might send an incorrect value, causing the client to terminate the transfer prematurely.
To overcome this issue, we can set up a local SFTP server that will handle the transfer correctly. This will allow us to transfer data between the client and the server without encountering the exit code 18 issue.
Setting Up a Local SFTP Server
To set up a local SFTP server, we can use a tool like OpenSSH. OpenSSH is a free and open-source implementation of the SSH protocol, which provides secure encrypted communications between two hosts over an insecure network.
To install OpenSSH on your local machine, you can use the following command:
sudo apt-get install openssh-server
Once OpenSSH is installed, you can start the SFTP server by running the following command:
sudo service ssh start
Now that the SFTP server is running, we can configure it to handle the transfer correctly. To do this, we need to modify the SFTP configuration file.
The SFTP configuration file is located at /etc/ssh/sshd_config. You can open this file using a text editor like nano:
sudo nano /etc/ssh/sshd_config
Once the file is open, we need to add the following line to the end of the file:
TCPKeepAlive yes
This line will ensure that the SFTP server sends keep-alive messages to the client, preventing the transfer from terminating prematurely.
Once the configuration file is modified, we need to restart the SFTP server for the changes to take effect:
sudo service ssh restart
Testing the SFTP Server
Now that the SFTP server is set up and configured correctly, we can test it by transferring a file from the Amazon Linux 2 server to the local machine. To do this, we can use the following CURL command:
curl -T /path/to/file.txt sftp://localhost
This command will transfer the file.txt file from the Amazon Linux 2 server to the local SFTP server.
- In this article, we discussed a peculiar issue that arises when using CURL on an Amazon Linux 2 server, which results in a failure with exit code 18 and the transfer of only around 1 MB of data.
- We troubleshot this issue by setting up a local SFTP server using OpenSSH.
- We modified the SFTP configuration file to ensure that the SFTP server sends keep-alive messages to the client, preventing the transfer from terminating prematurely.
- We tested the SFTP server by transferring a file from the Amazon Linux 2 server to the local machine using the CURL command.