/boot Keeps Filling Up On Kernel Update

This is an issue I encountered in one of my friend's ubuntu 16.04 box. He tried to do kernel update, but the /boot keeps filling up with old initramfs image files, making the update process failed. Then I found a post here, that says that if /var/lib/initramfs-tools is not being cleaned up from old kernel files, /boot will keep on being filled up with old initramfs images. So to clean it up:

# uname -r 

4.15.0-46-generic

# cd /var/lib/initramfs-tools

# rm `ls | grep -v 4.15.0-46`

Once cleaned up, update your current initramfs, using:

# update-initramfs -u -k all

where -u is to generate initramfs for current kernel, and '-k all' to generate initramfs for kernel version newer than current kernel.

Once that done, you can safely reboot your machine. It will be rebooted using the latest kernel.

Rename and Remount LVM Logical Volume

A usual scenario where rename and remount of LVM logical volume are needed, is when you install a box with a CentOS, and use the default LVM based partitioning scheme. This scheme will take 50G for your / partition, and the rest will be allocated to your /home, which is not practical. In this example, we will be remounting logical volume originally mounted to /home, to /var/lib/elasticsearch, renaming it along the way.

The original partition scheme 

# df -Th

Filesystem                   Type      Size  Used Avail Use% Mounted on

/dev/mapper/cl-root          xfs        50G  3.0G   48G   6% /

/dev/sda1                    xfs      1014M  179M  836M  18% /boot

/dev/mapper/cl-home xfs       965G   42G  924G   5% /home

Stop the service that might be using the partition that we are going to change

# systemctl stop elasticsearch

Rename the original directory to other name

# mv /var/lib/elasticsearch /var/lib/elasticsearch-old

Create a new directory to replace the one we already renamed above

# mkdir /var/lib/elasticsearch

Unmount /home

# umount /home

Check the name of volume group and logical volume

# lvs

Rename the logical volume to the one we desired. This is totally optional. You can use -t flag to test out the renaming process before proceeding

# lvrename -t cl home elasticsearch

# lvrename cl home elasticsearch

Change /etc/fstab to reflect on the new logical volume name and mount point. Test it out without the  -i option, before permanently make the change using the -i option

# sed 's/cl-home/cl-elasticsearch/g;s/\/home/\/var\/lib\/elasticsearch/g' /etc/fstab

# sed -i 's/cl-home/cl-elasticsearch/g;s/\/home/\/var\/lib\/elasticsearch/g' /etc/fstab

Mount it

# mount -a

Check to see if your new directory and logical volume mounted properly

# df -Th

Filesystem                   Type      Size  Used Avail Use% Mounted on

/dev/mapper/cl-root          xfs        50G  3.0G   48G   6% /

/dev/sda1                    xfs      1014M  179M  836M  18% /boot

/dev/mapper/cl-elasticsearch xfs       965G   42G  924G   5% /var/lib/elasticsearch

Move the content of /var/lib/elasticsearch to /home

# mv /var/lib/elasticsearch/* /home

Move the content of /var/lib/elasticsearch-old to /var/lib/elasticsearch

# mv /var/lib/elasticsearch-old/* /var/lib/elasticsearch

Remove /var/lib/elasticsearch-old

# rmdir /var/lib/elasticsearch-old

Set proper permission for /var/lib/elasticsearch

# chmod 750 -R /var/lib/elasticsearch

# chown -R elasticsearch.elasticsearch /var/lib/elasticsearch

Start your service

# systemctl start elasticsearch

Done.

Run an Application with GUI with Docker

There are a few ways to achieve this, like vnc and ssh X forwarding. But in this post, I will show how to run firefox by sharing the .Xauthority file with the docker instance.

First, create a Dockerfile in a directory called docker that use an ubuntu image from dockerhub, and install the firefox application

$ mkdir docker

$ cd docker

$ cat > Dockerfile

FROM ubuntu

RUN apt update && apt install -y firefox

CMD ["/usr/bin/firefox"]

Press ctrl-d to save the file

Next, build an image using the above Dockerfile

$ sudo docker build --tag=firefox-app docker/

Then, run the image, with additional options of --network and --env, and sharing our host .Xauthority file with the container that we are going to run 

$ sudo docker run --network=host --env="DISPLAY" --volume="$HOME/.Xauthority:/root/.Xauthority:rw" --name=firefox1 firefox-app

You should be able to get a working firefox, running from a docker container, separated from the current firefox that you have in your current machine

Credit: https://medium.com/@SaravSun/running-gui-applications-inside-docker-containers-83d65c0db110

Install vncserver on Ubuntu 18.04 desktop

In this guide, we will be using tigervnc server

Install the vncserver
$ sudo apt update; sudo apt install tigervnc-standalone-server tigervnc-xorg-extension -y

Setup a password for vncserver
$ vncpasswd

Once you have provided the password, make sure a passwd file is created
$ ls ~/.vnc/
passwd

Run below command to put some settings in ~/.vnc/xstartup, so that gnome will be started when vnc is used
$ cat > ~/.vnc/xstartup <<EOF
#!/bin/sh
# Start Gnome 3 Desktop 
[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
vncconfig -iconic &
dbus-launch --exit-with-session gnome-session &
EOF

Press ctrl-d to save the above file

Start a vncserver instance
$ vncserver

List the display to get the port number to connect to, in this example the port number would be 5901, since the display number is 1
$ vncserver -list 

TigerVNC server sessions:

X DISPLAY # PROCESS ID
:1 5375

In the client machine, connect with using vncviewer like below, replacing the x.x.x.x with your server's ip number
$ vncviewer x.x.x.x:5901


To terminate the vnc session, use below command to kill the first instance of the vncserver
$ vncserver -kill :1

Install xrdp on Ubuntu 18.04 desktop

Install xrdp

$ sudo apt-get -y install xrdp

Next, one may adjust the configuration file:

$ sudo nano /etc/xrdp/xrdp.ini

Set encryption level to high, and save xrdp.ini:

encrypt_level=high

Allow just RDP through the local firewall:

$ sudo ufw allow 3389/tcp

Create a polkit configuration file:

$ sudo nano /etc/polkit-1/localauthority.conf.d/02-allow-colord.conf 

and put below settings into the file:

polkit.addRule(function(action, subject) {

if ((action.id == “org.freedesktop.color-manager.create-device” || action.id == “org.freedesktop.color-manager.create-profile” || action.id == “org.freedesktop.color-manager.delete-device” || action.id == “org.freedesktop.color-manager.delete-profile” || action.id == “org.freedesktop.color-manager.modify-device” || action.id == “org.freedesktop.color-manager.modify-profile”) && subject.isInGroup(“{group}”))

{

return polkit.Result.YES;

}

});

Restart xrdp

$ sudo systemctl restart xrdp

Logout all user from your desktop

Connect using remote desktop client. For linux, you can use remmina.

P/S: If you are still unable to login using remote desktop client, check whether you have xorgxrdp package installed. If not, install it and restart xrdp. Then try to connect again

$ sudo apt install xorgxrdp -y
$ sudo systemctl restart xrdp