How to change max open files for nginx server on Ubuntu

Posted on January 8, 2020 by

The following error occurred a lot in /var/log/nginx/error.log:

Too many open files

This means that the nginx master process reached the maximum number of open files which was set to the default of 4096. (To check it, simply cat /proc/pid/limits, where pid is the process id)

To resolve, this, edit /lib/systemd/system/nginx.service and add the following line:

LimitNOFILE=30000 #change it according to your needs

Then reload the systemctl daemon:

sudo systemctl daemon-reload

and finally restart the nginx service:

sudo service nginx restart

That’s it, the error is gone!

Tested on Ubuntu 16.04 with nginx 1.17, should work with any other OS using systemd.

Enjoy!

Sources:

https://unix.stackexchange.com/questions/281684/configuring-ulimit-of-max-open-files-for-daemonized-nginx-master-process

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Add a new HDD to a VM without rebooting on Ubuntu server

Posted on December 30, 2019 by

Firstly, install scsitools package:

sudo apt install scsitools

Then run the command rescan-scsi-bus:

sudo rescan-scsi-bus

That’s it, your new virtual HDD has now been detected.

Another way would be to do it with a loop and without the need for that package:

for host in ls /sys/class/scsi_host/; do
echo "- - -" > /sys/class/scsi_host/${host}/scan;
done

Enjoy!

Sources:

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A cute little screenshot and annotation tool on Linux

Posted on November 14, 2019 by

A very handy screenshot tool that works very well on my KDE plasma desktop on Ubuntu 19.10 is ksnip, which you can get from here: https://github.com/damirporobic/ksnip

Just download and install the deb file and that’s it!

Enjoy!

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Restart network manager indicator in KDE Plasma Desktop

Posted on November 11, 2019 by 
sudo service NetworkManager restart

Note: This is specifically for the network icon in the system tray and is different from the network-manager service which controls the whole Linux network manager:

Tested on Ubuntu 19.10 with KDE Plasma 5.16.5

Source: https://bbs.archlinux.org/viewtopic.php?id=200935

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Copy with rsync over ssh

Posted on October 30, 2019 by

From remote server to local one:

rsync -avzhe ssh remote_user@REMOTE_IP:/remote_folder_or_file /local_destination_folder_or_file

From local server to remote one:

rsync -avzhe ssh local_folder_or_file remote_user@REMOTE_IP:/remote_destination_folder_or_file

That’s it, Enjoy!

Sources:

Rsync (Remote Sync): 10 Practical Examples of Rsync Command in Linux

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Build Synergy in Ubuntu 19.04

Posted on October 10, 2019 by

Synergy software, which shares your keyboard and mouse to multiple computers through the network, is no longer available in the Ubuntu 19.04 repos, so the only remaining option is to build it from source:

sudo apt install qtcreator qtbase5-dev cmake make g++ xorg-dev libssl-dev libx11-dev libsodium-dev libgl1-mesa-glx libegl1-mesa libcurl4-openssl-dev libavahi-compat-libdnssd-dev qtdeclarative5-dev libqt5svg5-dev libsystemd-dev git build-essential
git clone https://github.com/symless/synergy-core.git
cd synergy
mkdir build
cd build
cmake ..
make
sudo make install

That’s it, Enjoy!

Note: After starting Synergy, you don’t have to enter the serial to get basic functionality, just cancel and you are good to go.

Source: https://github.com/symless/synergy-core/wiki/Compiling

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Fix icon and text size for hidpi displays on login screen in KDE on Ubuntu 19.04

Posted on June 17, 2019 by

Just create/edit the file /etc/sddm.conf and add the following:

[X11]
 EnableHiDPI=true
 ServerArguments=-nolisten tcp -dpi 192

Reboot, and you’re good to go, Enjoy!

Sources: https://www.reddit.com/r/kde/comments/amybg5/login_screen_on_hidpi_4k_screen/

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