Ubuntu Troubleshootings

Ubuntu cannot restart or shutdown properly.
- In file /etc/default/grub, change line from GRUB_CMDLINE_LINUX_DEFAULT="quiet splash" to GRUB_CMDLINE_LINUX_DEFAULT="quiet splash acpi=force".
- Then run update-grub.
Install another language input.

Go to system settings, click + sign to add a new input source.
Select the input you want, like Chinese (Cangjie).
If the input does not exist, go to terminal and type sudo apt-get update and sudo apt-get install ibus-cangjie.
It should appear now. Add it to your language input. Switch between inputs with Win + Space.

No screen recorder.

Before 18.04, screen recorder is not installed as default.
Go to Ubuntu Software. install vokoscreenNG.
Otherwise, just press Shift+Ctrl+Alt+R, to start recording after version 18.04.

Partition and Mount

During dualboot, you might want to split partition. One way is to use GParted sudo apt-get install gparted.
You can start shrinking and splitting new partition, by sudo gparted. Once you get in, choose a big partition, and split it into smaller one.
Bear in mind that, windows cannot access to ext4 file system, but ubuntu can access both ext4 and ntfs. NTFS is usually used by windows, EXT4 for linux.
To make the partition readable from terminal file structure, you need to mount. If there is a missing Mount Point in GParted for a partition, go to terminal. sudo mkdir /backup and sudo mount /dev/nvme0n1p8 /backup.
Now if you check by df -h, Mount on column will show.
You can even mount windows ntfs for ubuntu to use. sudo mkdir /windows, sudo mount /dev/nvme0n1p1 /windows. Inside it, you can see files from windows. In /windows, I create ubuntu/ folder which contains docs/ data/ projects/ outputs/ folders just for isolation.

Error when using apt-get

The error looks like this,


E: Could not get lock /var/lib/dpkg/lock - open (11 Resource temporarily unavailable)
E: Unable to lock the administration directory (/var/lib/dpkg/) is another process using it?

Fix by,


sudo rm /var/lib/apt/lists/lock
sudo rm /var/cache/apt/archives/lock
sudo rm /var/lib/dpkg/lock

Keyboard and Mouse not working at login screen

Install xserver-xorg-input.


sudo apt-get install xserver-xorg-input-all

Send messages between Ubuntu PCs

Can use ssh and libnotify-bin


sudo apt-get install ssh libnotify-bin
ssh username@ip
export DISPLAY=:0
notify-send "Title of message" "message text"

Debian -- Cannot find Network Manager

Start the network manager service by,


sudo /etc/init.d/network-manager start

Ubuntu -- No wired connection - Wired unmanaged

Edit network manager configuration.


sudo vim /etc/NetworkManager/NetworkManager.conf
##
managed=false -→ true
##
sudo service network-manager restart

Ubuntu desktop installed shows wired unmanaged (more for vm)


cd /etc/netplan
sudo cp 50-cloud-init.yaml 50-cloud-init_copy.yaml
sudo vim 50-cloud-init.yaml
##
network:
    renderer: NetworkManager ### add this
...
##
sudo netplan apply

Delete User

Try deleting username with,


sudo userdel username
sudo rm -r /home/username

If there is a warning "user is currently used by process id", kill the process by,


sudo kill processid

How to kill a process on a port on Ubuntu


sudo kill -9 `sudo lsof -t -i:port`

The following signatures couldn't be verified.

Occur when sudo apt update.
It shows W: GPG error: http://repo.{}... The following signature: NO_PUBKEY {key}.
To fix it,


sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-keys {key}

Ubuntu Troubleshootings

References