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SFTP Ubuntu 18.04

Filed under: Uncategorized — Mathz @ 20:15


SFTP stands for SSH File Transfer Protocol. As its name suggests, it’s a secure way to transfer files between machines using an encrypted SSH connection. Despite the name, it’s a completely different protocol than FTP (File Transfer Protocol), though it’s widely supported by modern FTP clients.

SFTP is available by default with no additional configuration on all servers that have SSH access enabled. It’s secure and easy to use, but comes with a disadvantage: in a standard configuration, the SSH server grants file transfer access and terminal shell access to all users with an account on the system.

In some cases, you might want only certain users to be allowed file transfers and no SSH access. In this tutorial, we’ll set up the SSH daemon to limit SFTP access to one directory with no SSH access allowed on per-user basis.


To follow this tutorial, you will need access to an Ubuntu 18.04 server. This server should have a non-root user with sudo privileges, as well as a firewall enabled. For help with setting this up, follow our Initial Server Setup Guide for Ubuntu 18.04.

Step 1 — Creating a New User

First, create a new user who will be granted only file transfer access to the server. Here, we’re using the username sammyfiles, but you can use any username you like.

  • sudo adduser sammyfiles

You’ll be prompted to create a password for the account, followed by some information about the user. The user information is optional, so you can press ENTER to leave those fields blank.

You have now created a new user that will be granted access to the restricted directory. In the next step we will create the directory for file transfers and set up the necessary permissions.

Step 2 — Creating a Directory for File Transfers

In order to restrict SFTP access to one directory, we first have to make sure the directory complies with the SSH server’s permissions requirements, which are very particular.

Specifically, the directory itself and all directories above it in the filesystem tree must be owned by root and not writable by anyone else. Consequently, it’s not possible to simply give restricted access to a user’s home directory because home directories are owned by the user, not root.

Note: Some versions of OpenSSH do not have such strict requirements for the directory structure and ownership, but most modern Linux distributions (including Ubuntu 18.04) do.

There are a number of ways to work around this ownership issue. In this tutorial, we’ll create and use /var/sftp/uploads as the target upload directory. /var/sftp will be owned by root and will not be writable by other users; the subdirectory /var/sftp/uploads will be owned by sammyfiles, so that user will be able to upload files to it.

First, create the directories.

  • sudo mkdir -p /var/sftp/uploads

Set the owner of /var/sftp to root.

  • sudo chown root:root /var/sftp

Give root write permissions to the same directory, and give other users only read and execute rights.

  • sudo chmod 755 /var/sftp

Change the ownership on the uploads directory to sammyfiles.

  • sudo chown sammyfiles:sammyfiles /var/sftp/uploads

Now that the directory structure is in place, we can configure the SSH server itself.

Step 3 — Restricting Access to One Directory

In this step, we’ll modify the SSH server configuration to disallow terminal access for sammyfiles but allow file transfer access.

Open the SSH server configuration file using nano or your favorite text editor.

  • sudo nano /etc/ssh/sshd_config

Scroll to the very bottom of the file and append the following configuration snippet:

. . .

Match User sammyfiles
ForceCommand internal-sftp
PasswordAuthentication yes
ChrootDirectory /var/sftp
PermitTunnel no
AllowAgentForwarding no
AllowTcpForwarding no
X11Forwarding no

Then save and close the file.

Here’s what each of those directives do:

  • Match User tells the SSH server to apply the following commands only to the user specified. Here, we specify sammyfiles.
  • ForceCommand internal-sftp forces the SSH server to run the SFTP server upon login, disallowing shell access.
  • PasswordAuthentication yes allows password authentication for this user.
  • ChrootDirectory /var/sftp/ ensures that the user will not be allowed access to anything beyond the /var/sftp directory.
  • AllowAgentForwarding noAllowTcpForwarding no. and X11Forwarding no disables port forwarding, tunneling and X11 forwarding for this user.

This set of commands, starting with Match User, can be copied and repeated for different users too. Make sure to modify the username in the Match User line accordingly.

Note: You can omit the PasswordAuthentication yes line and instead set up SSH key access for increased security. Follow the Copying your Public SSH Key section of the SSH Essentials: Working with SSH Servers, Clients, and Keys tutorial to do so. Make sure to do this before you disable shell access for the user.

In the next step, we’ll test the configuration by SSHing locally with password access, but if you set up SSH keys, you’ll instead need access to a computer with the user’s keypair.

To apply the configuration changes, restart the service.

  • sudo systemctl restart sshd

You have now configured the SSH server to restrict access to file transfer only for sammyfiles. The last step is testing the configuration to make sure it works as intended.

Step 4 — Verifying the Configuration

Let’s ensure that our new sammyfiles user can only transfer files.

Logging in to the server as sammyfiles using normal shell access should no longer be possible. Let’s try it:

  • ssh sammyfiles@localhost

You’ll see the following message before being returned to your original prompt:

Error message
This service allows sftp connections only.
Connection to localhost closed.

This means that sammyfiles can no longer can access the server shell using SSH.

Next, let’s verify if the user can successfully access SFTP for file transfer.

  • sftp sammyfiles@localhost

Instead of an error message, this command will show a successful login message with an interactive prompt.

SFTP prompt
Connected to localhost.

You can list the directory contents using ls in the prompt:

  • ls

This will show the uploads directory that was created in the previous step and return you to the sftp> prompt.

SFTP file list output

To verify that the user is indeed restricted to this directory and cannot access any directory above it, you can try changing the directory to the one above it.

  • cd ..

This command will not give an error, but listing the directory contents as before will show no change, proving that the user was not able to switch to the parent directory.

You have now verified that the restricted configuration works as intended. The newly created sammyfiles user can access the server only using the SFTP protocol for file transfer and has no ability to access the full shell.


You’ve restricted a user to SFTP-only access to a single directory on a server without full shell access. While this tutorial uses only one directory and one user for brevity, you can extend this example to multiple users and multiple directories.

The SSH server allows more complex configuration schemes, including limiting access to groups or multiple users at once, or even limited access to certain IP addresses. You can find examples of additional configuration options and explanation of possible directives in the OpenSSH Cookbook. If you run into any issues with SSH, you can debug and fix them with this troubleshooting SSH series.


Flicd on Raspberry PI 3

Filed under: Uncategorized — Mathz @ 19:34

curl -sSL | sh

sudo usermod -aG docker pi

sudo docker run hello-world

sudo apt-get install libffi-dev libssl-dev python python-pip

sudo pip install docker-compose


Automatically owned by www-data

Filed under: Hemsidor,PHP — Mathz @ 09:50

To make sure any file or folder you create in /var/www/html gets automatically owned by www-data you can use inotify, it’s like cron but monitors folders/files for changes in attribuets, file creations, modifications and much more.

First install it with:

$ sudo apt-get install incron

Allow root to use incron by opening /etc/incron.allow with:

$ sudo vim /etc/incron.allow

and add root to the file, then save and exit.

Edit your incrontab with:

$ sudo incrontab -u root -e

and add the following line to it:

/var/www/html IN_CREATE /bin/chown -R www-data:www-data /var/www/html/

save and exit.

Now as soon as a file is created in the /var/www/html direcotry it will automatically set onwership to www-data:www-data.

Explanation of the line in incrontab:

/var/www/html is the directory that will be monitored.

IN_CREATE will watch for created files. It’s the file change mask.

/bin/chown -R www-data:www-data /var/www/html/ is the command/action to execute.


How do I run graphical programs remotely from a Linux server?

Filed under: Server,Ubuntu — Mathz @ 20:19

It is common for users of the Ubuntu Linux systems to want to run graphical applications (such as matlab, mathematica, eclipse, etc) on these Linux servers and display them on their local computers.  This document details the steps required to do this for Mac

Mac OS X

  1. Install XQuartz on your Mac, which is the official X server software for Mac
  2. Run Applications > Utilities >
  3. Right click on the XQuartz icon in the dock and select Applications > Terminal.  This should bring up a new xterm terminal windows.

  4. In this xterm windows, ssh into the linux system of your choice using the -X argument (secure X11 forwarding).  For example, to log into you would run something like:

         ssh -Y

  5. Once you are logged into the linux system, you can just run the GUI program of your choice (ie. matlab, mathematics, etc) and it will display on your Mac.


Ubuntu 18.04 root DNS update

Filed under: Server,Ubuntu — Mathz @ 00:09
Såg detta i min log fil  
checkhints: ( missing from hints 

Jag åtgärda det genom följande kommando

sudo wget --user=ftp --password=ftp -O /etc/bind/db.root


Disable SELinux Centos 7

Filed under: Centos,Server — Mathz @ 16:19

Temporery disable SELinux
sudo setenforce 0

/etc/selinux/config file and set the SELINUX mod to disabled

# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
# enforcing – SELinux security policy is enforced.
# permissive – SELinux prints warnings instead of enforcing.
# disabled – No SELinux policy is loaded.
# SELINUXTYPE= can take one of these two values:
# targeted – Targeted processes are protected,
# mls – Multi Level Security protection.


How to move docker’s default /var/lib/docker to another directory on Ubuntu/Debian Linux

Filed under: Docker,Server — Mathz @ 11:00

The following config will guide you through a process of changing the docker’s default /var/lib/docker storage disk space to another directory. There are various reasons why you may want to change docker’s default directory from which the most obvious could be that ran out of disk space. The following guide should work for both Ubuntu and Debian Linux or any other systemd system. Make sure to follow this guide in the exact order of execution.

Let’s get started by modifying systemd’s docker start up script. Open file /lib/systemd/system/docker.service with your favorite text editor and replace the following line where /new/path/docker is a location of your new chosen docker directory:

ExecStart=/usr/bin/docker daemon -H fd://
ExecStart=/usr/bin/docker daemon -g /new/path/docker -H fd://

When ready stop docker service:

# systemctl stop docker

It is important here that you have completely stopped docker daemon. The following linux commandwill yield no output only if docker service is stopped:

# ps aux | grep -i docker | grep -v grep

If no output has been produced by the above command, reload systemd daemon:

# systemctl daemon-reload

Once this is done create a new directory you specified above and optionally rsync current docker data to a new directory:

# mkdir /new/path/docker
# rsync -aqxP /var/lib/docker/ /new/path/docker

At this stage we can safely start docker daemon:

# systemctl start docker

Confirm that docker runs within a new data directory:

#  ps aux | grep -i docker | grep -v grep
root      2095  0.2  0.4 664472 36176 ?        Ssl  18:14   0:00 /usr/bin/docker daemon -g  /new/path/docker -H fd://
root      2100  0.0  0.1 360300 10444 ?        Ssl  18:14   0:00 docker-containerd -l /var/run/docker/libcontainerd/docker-containerd.sock --runtime docker-runc

All done.


Firewall Centos

Filed under: Uncategorized — Mathz @ 16:54
sudo firewall-cmd --zone=public --add-port=80/tcp --permanent sudo firewall-cmd --reload


Ubuntu Server

Filed under: Uncategorized — Mathz @ 10:46

To configure a static IP address on your Ubuntu 18.04 server you need to modify a relevant netplan network configuration file within /etc/netplan/ directory. 

For example you might find there a default netplan configuration file called 01-netcfg.yaml or 50-cloud-init.yaml with a following content instructing the networkd deamon to configure your network interface via DHCP:

# This file describes the network interfaces available on your system
# For more information, see netplan(5).
  version: 2
  renderer: networkd
      dhcp4: yes

To set your network interface ens160 to static IP address with gateway and DNS server as replace the above configuration with the one below.

# This file describes the network interfaces available on your system
# For more information, see netplan(5).
  version: 2
  renderer: networkd
     dhcp4: no
     addresses: []
       addresses: []

Once ready apply changes with:

$ sudo netplan apply

In case you run into some issues execute:

$ sudo netplan --debug apply


Catalina.out is emtpy

Filed under: Uncategorized — Mathz @ 19:28

journalctl -u tomcat

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