How can we reset apache2 - apache2

By mistake I have applied the command,
sudo rm -rf /etc/init.d/apache2 restart
after that i can't run apache2
How can I solve this?

Do as below:
sudo apt-get purge apache2
sudo apt-get install apache2
sudo service apache2 start

If Apache2 is installed as part of a system package (e.g. with Debian apt-get), then you should be able to get it back by removing and reinstalling the package (I hesitate to say use e.g. the reinstall option because I don't think that touches config files). You could also fetch the source package and find the init.d file in that and copy it back.

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How to install ROS on Ubuntu 18.04?

Im running Ubuntu 18.04 and trying to install ROS for the first time on my machine. I have tried to follow the instructions at: http://wiki.ros.org/melodic/Installation/Ubuntu
I get stuck at this part.
sudo apt-get install ros-melodic-desktop-full
My attempts:
sudo apt -f install
sudo apt update --fix-missing
sudo dpkg --configure -a
sudo dpkg --remove --force-remove--reinstreq
sudo apt clean
sudo apt update
sudo rm /var/lib/apt/lists/lock
sudo rm /var/cache/apt/archives/lock
Nothing has worked so far.
Terminal commands:
$sudo apt-get install ros-melodic-desktop-full
Reading package lists… Finished
Builds dependency trees
Reading state information ... Finished
Some packages could not be installed. It may mean that you have requested
an impossible situation or, if you use the unstable distribution
that some necessary packages have not yet been created or moved
from "Incoming".
The following information may help to resolve the situation:
The following packages have dependencies that cannot be satisfied:
rose-melodic-desktop-full: Dependent on: rose-melodic-desktop but it will not be installed
Depending on: rose-melodic-perception but it will not be installed
Depending on: rose-melodic-simulators but it will not be installed
Depending on: ros-melodic-urdf-sim-tutorial but it will not be installed
E: Could not correct the problems, you have withheld broken packages.
Please help me install ROS
1 - After following ROS melodic Installation first steps (see link below), Try to install it with the link "click here" below the "sudo apt install ros-melodic-desktop-full" line
ROS melodic Installation page
If it's doesn't work
2 - check, "Software & Update" parameters
(if you cannot find it: launch "Ubuntu Software Center" and in the menu bar, on top, select "Software & Update")
In "Other Sofware" tab, the link
"http://pacckage.ros.org/ros/ubuntu bionic main"
is printed, and in "Autentication" tab a key from Open Robotics is printed
3 - Try to do 1- again, if it doesn't work, follow 4-
4 - In "Updates" tab, check "recommanded Updates", launch "Update Manager" and install updates (I don't do it properly on my PC)
5 - And finally you need to install manually rosdep with:
"sudo apt-get install python-rosdep"
Ubuntu (apt) does NOT allow packages with the same name but different versions to be installed.
Remove other versions first. For example: apt remove ros-desktop*
first of all install program on ubuntu.
sudo apt-get update
sudo apt-get upgrade
after update packet try follow the instructions at: enter link description here again
I got it working like so:
Install deps:
sudo apt install gazebo9-common libgazebo9-dev gazebo9 ros-melodic-gazebo-ros-pkgs ros-melodic-gazebo-dev ros-melodic-gazebo-ros-control ros-melodic-gazebo-ros ros-melodic-urdf-sim-tutorial ros-melodic-simulators
Install ros melodic
sudo apt-get install ros-melodic-desktop-full

Apache start libphp7.3.so not found

I have Install php 7.3 and apache2 but when I try to start apache2 , I have this error :
service apache2 start
apache2: Syntax error on line 146 of /etc/apache2/apache2.conf: Syntax error on line 3 of /etc/apache2/mods-enabled/php7.3.load: Cannot load /usr/lib/apache2/modules/libphp7.3.so into server: /usr/lib/apache2/modules/libphp7.3.so: cannot open shared object file: No such file or directory
I really don't know how to resolve this problem, I have tried to remove and reinstall without success.
You're getting that error because the PHP 7.3 library for Apache is not installed.
sudo apt install -y libapache2-mod-php7.3
The above command should fix it.
It solved my problem:
sudo add-apt-repository ppa:ondrej/php
sudo apt-get update
sudo apt-get install php7.3
sudo apt-get install php7.3-cli php7.3-common php7.3-json php7.3-opcache php7.3-mysql php7.3-mbstring php7.3-zip php7.3-fpm php7.3-intl php7.3-simplexml
sudo service apache2 restart
For me the problem was that I did not install apache tools for php.
On arch linux:
yaourt -S php-apache
After that, module appeared in the folder.
The best way not to make a mistake is to follow guide: https://wiki.archlinux.org/title/Apache_HTTP_Server#PHP

MongoDB not starting after downgrade

MongoDB automatically updated to 3.6 after doing a system update and was no longer compatible with my old dataset. So I downgraded to 3.4 again, however now the mongo instance won't start at all and exits with error code 100. Any help would be appreciated.
There were a series of issues piggybacking on one another here, but I sorted this out.
Firstly I reverted from 3.6 to 3.4 by uninstalling Mongo:
sudo service mongod stop
sudo apt-get purge mongodb-org*
Then I installed the specific version of Mongo:
apt-get install mongodb-org=3.4.1 mongodb-org-server=3.4.1 mongodb-org-shell=3.4.1 mongodb-org-mongos=3.4.1 mongodb-org-tools=3.4.10
Then I deleted the .lock files:
rm -rf /path/to/mongod.lock
rm -rf /path/to/WiredTiger.lock
Next you have to grant permissions to Mongo again:
sudo systemctl enable mongod
(Make sure the dbpath is correct in /etc/mongod.conf. If you want to make any changes to the mongod.service file, do it now, and remember to run systemctl daemon-reload to set the changes.)
Then finish updating permissions:
sudo chown -R mongodb:mongodb /var/lib/mongodb
sudo chown -R mongodb:mongodb /var/log/mongodb
Now service mongod start or sudo systemctl mongod start should work.
Here are links to some of the resources I found helpful:
Installing Mongo on Ubunut
Uninstalling MongoDB
Installing a specific version of Mongo
Setting Mongo file permissions

Update Apache 2.4.34 to 2.4.35 in Ubuntu 16.04

I have tried the following first in Ubuntu Server
sudo apt-get update
sudo apt-get upgrade
No signs of software updates in the Ubuntu Server repository.
So I went ahead with PPA with the following
add-apt-repository ppa:ondrej/apache2
apt-get update
apt-get upgrade
OR
sudo add-apt-repository ppa:ondrej/apache2
sudo apt update
sudo apt install apache2
But no luck as PPA is having 2.4.34 as the latest one.
NOTE: Even I restarted and check with stopping and starting my Apache2
server.
But seems nothing working is there any other way I can update it to the latest version. This is important as our project is stuck with a Security Assessment.
And in version 2.4.34 there is DDOS security vulnerability. And has been fixed in 2.4.35
Can anyone help me out with updating apache2, even redirects to any sites or links are welcome.
All you need to download this version and enjoy , just
install it manually https://httpd.apache.org/download.cgi

Install Adminer on Ubuntu 18.04 bionic

I'm trying to install Adminer from Ubuntu repository using:
sudo apt install adminer
Installation works fine but can't find the file /etc/adminer/apache.conf to use with Apache server. The folder /etc/adminer/ is empty and can't find it anywhere with find command.
Any help?
Thanks in advance.
In the next few steps, I'll show you how I installed adminer for Ubuntu 18.04.1 LTS .
After installation with apt package manager change into the adminer directory.
cd /usr/share/adminer
There you will find a file called compile.php.
Run the following command and the adminer-X.X.X.php (X.X.X for your version) file will be created.
sudo php compile.php
Create the apache adminer configuration file.
sudo echo "Alias /adminer.php /usr/share/adminer/adminer-X.X.X.php" | sudo tee /etc/apache2/conf-available/adminer.conf
Now you'll need to activate the configuration.
cd /etc/apache2/conf-available/
sudo a2enconf adminer.conf
Reload your apache webserver.
sudo systemctl reload apache2.
Test in your browser of choice (localhost/adminer.php)
This source was really helpful:
https://www.linuxhelp.com/how-to-install-adminer-on-ubuntu-16-04/
Install Apache:
sudo apt-get install apache2
Install PHP:
sudo apt-get install php libapache2-mod-php php-mysql
Install Adminer:
sudo wget "http://www.adminer.org/latest.php" -O /var/www/html/adminer.php
Once the installation completes, restart Apache.
sudo service apache2 restart
At this point, the setup is complete. You can access Adminer at the following address.
http://[SERVER_IP]/adminer.php

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