Ubuntu 18.04 LTS came out recently with Gnome desktop as default. Unfortunately even in 2018, it won't remember the external monitor positioning after reboot and has no support in display settings to set per-display scaling. Year of the Linux desktop, anyone?

Xrandr is a powerful Linux tool to manipulate displays. Unfortunately, the man page is very sparse on information with badly explained flags and various Linux guides are no better.

This example will create a triple monitor setup with HiDPI laptop display at the bottom of the array.

Xrandr command:

xrandr --fbmm 11520x4200 --output eDP --pos 4320x2400 --mode 2880x1800 --scale 1x1 --primary --output DisplayPort-1 --pos 0x0 --mode 1920x1200 --scale 2x2 --output DisplayPort-0 --pos 3840x0 --mode 1920x1200 --scale 2x2 --output HDMI-0 --pos 7680x0 --mode 1920x1200 --scale 2x2

 

Gnome scaling is set to 200% so our HiDPI native display looks normal. Unfortunately this also means non-HiDPI displays have this scaling applied which is not what we want.

Framebuffer is the full outer rectangle which must be able to contain our display setup as a whole.

Since external displays are scaled 2×2 (zoom out), they take twice the size of their actual resolution in our framebuffer. Meaning their sizes in fb are actually 3840×2400.

Y of the framebuffer is therefore 2400+1800=4200 (HiDPI display is scaled 1×1 so it takes the same amount of space in the framebuffer as it's resolution).

X of the framebuffer is 3*3840=11520.

–fbmm specifies the full framebuffer size

–pos specifies the position of the display in the buffer. 0x0 position starts on top-left corner.

–mode sets the actual display resolution

–output specifies the display output (run xrandr to list all available)

–scale specifies "zooming" in (<1) or out (>1)

 

The end result has some invisible area on the bottom-left and bottom-right corners so it is not ideal. I have yet to figure out if it is possible to specify fencing around that area.

The HiDPI display is also not perfectly aligned with the top display but that could be corrected with fractional scaling. It didn't really bother me to fiddle with that.

Finally, you should run this command with a startup script so you get the correct monitor positioning and scaling after login.

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We had a peculiar situation where both PHP5 and PHP7 were needed at the same time on a FreeBSD server. It was also prohibitive to get root or sudo access on the managing account. The solution was to compile PHP from source with fpm, run fpm on a UNIX socket and wire the specific domain which needed PHP7 through Nginx.

Compiling from source

Compiling PHP is pretty straightforward but you can easily forget crucial configure flags. First get the source archive. After trial and error, this appears to be "good enough" for Laravel 5.6 requirements.

./configure -prefix=/home/foo/php7 --with-openssl --enable-mbstring --with-pdo-mysql --enable-fpm --with-config-file-path=/home/foo/php7 --with-config-file-scan-dir=/home/foo/php7 --with-iconv --with-gmp --with-gd

Followed by

make && make install

copy php.ini-development file from source to the –with-config-file-path directory and call it php.ini.  In PREFIX/bin confirm that php binary is loading your ini file by running

./php --ini

If you made a mistake in your configure run, you have to make clean first or the changed options won't be picked up.

Configuring fpm

In your PREFIX/etc folder, check php-fpm.conf. The only lines I bothered to verify and edit were pid, error_log and include, the rest can be left as is.

Inside folder php-fpm.d create a config file like my.subdomain.conf and add something like

listen = /location/of/php-fpm.sock
user = foo
group = foo
pm = dynamic
pm.max_children = 5
pm.start_servers = 1
pm.min_spare_servers = 1
pm.max_spare_servers = 1
pm.max_requests = 200
listen.backlog = -1
pm.status_path = /status
request_terminate_timeout = 30s
rlimit_files = 131072
rlimit_core = unlimited
catch_workers_output = yes
env[HOSTNAME] = $HOSTNAME
env[TMP] = /tmp
env[TMPDIR] = /tmp
env[TEMP] = /tmp

You can study fpm config in great details but this is enough to get you going.

Now you can run your PHP7 fpm process in PREFIX/sbin with

./php-fpm --fpm-config /prefix/etc/php-fpm.conf

Since we don't have any init scripts in this case, we must be able to kill it also. Find it with

ps aux | grep fpm

and kill with

kill -QUIT pid

Make sure it says php-fpm: master process in the ps output, killing children doesn't do anything, just respawns them.

Now you just need to wire up your Nginx to use this fpm instead of the PHP5 system one by specifying

fastcgi_pass unix:/location/of/php-fpm.sock;

We now have PHP dualstack with some web apps running on system provided PHP5 and some on our own built PHP7. We did not need root for this process, except possibly for configuring Nginx.

One obvious downside is that you now have to take care of updating your PHP version on your own but that is one view we had to sacrifice. Updates should be relatively easy and fast since make install won't remove your config files in existing installation and compiling PHP takes just a few minutes.

 

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Error looks something like

Error response from daemon: driver "overlay" failed to remove root filesystem for 805c245dad451542b44bb1b58c60887fa98a64a61f2f0b8de32fa5b13ccc8ce4: remove /var/lib/docker/overlay/8f666b802f418f4a3dc4a6cafbefa79afc81491a5cb23da8084dd14e33afbea0/merged: device or resource busy

It usually appears when stopping and starting a container. It results in Docker container not being able to start or starts in a weird dead/removed state. Issue is presumably fixed in Centos 7.4 as per this github issue, but a workaround exists:

1. Grep by part of ID:

grep docker /proc/*/mountinfo | grep 8f66

it shows which process is holding up the mount in busy state

/proc/31415/mountinfo:…

2. Kill the process

sudo kill 31415

 

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This is a note to self about the release procedure and distro packaging of a development library.

This instructions expect aptly and createrepo to be preinstalled on your repo server together with a valid GPG key.

Packaging a .deb

1. Checkout the release tag and build the deb according to README. Each build should be done on the same machine as the target distribution. If I am packaging for Centos 6 I am also building on Centos 6. If CMake and CPack are set up correctly it usually boils down to:

cmake -G "Unix makefiles" -H./ -B./build
cd build
make
cpack -G "DEB"

If the project is missing CMake, refuse to package it.

2. Check that deb info is correct:

dpkg-deb -I bncsutil-1.4.1-Linux.deb

3. Rename it to distro you are building on, then scp to your repo server

mv bncsutil-1.4.1-Linux.deb bncsutil-1.4.1-Debian9.deb

4. If aptly repo does not exist yet, create it

aptly repo create -comment="Debian 9 repo" -component="main" -distribution="bnetdocs-stretch" debian9

Ideally you only create the repo the first time, for future updates you create a snapshot of it, add a package, then switch the repo to new snapshot. See aptly docs for more.

Alternatively, you can just add more packages and update the repo with

aptly publish update bnetdocs-stretch debian9

 

5. Add package to repo

aptly repo add debian9 deb_archives/bncsutil-1.4.1-Debian9.deb

6. Publish repo

aptly publish repo debian9 debian9

7. On target machine, add repo to /etc/apt/sources.list and fetch public key

deb http://apt.xpam.pl/debian8/ bnetdocs-stretch main

wget -qO - https://apt.xpam.pl/xpam.pl-pubkey.asc | sudo apt-key add -

8. Update and then check if package info is correct

apt-cache show bncsutil

9. If big mistakes were made

aptly publish drop debian9 debian9

..and start over. Repeat for Debian 8 etc.

Packaging an .rpm

1. See the previous #1. The only difference is

cpack -G "RPM"

2. Check that rpm info is correct

rpm -qip bncsutil-1.4.1-Linux.rpm

3. Rename it to distro you are building on, then scp to your repo server

mv bncsutil-1.4.1-Linux.rpm bncsutil-1.4.1-Centos7.rpm

4. Make sure you have .rpmmacros file in home dir with uid of gpg signing key (check out your keys with gpg –list-keys). If you don't have one, generate it. Entry in the file should look like:

%_gpg_name <uid here>

5. Sign rpm

rpm --addsign rpm_archives/bncsutil-1.4.1-Centos7.rpm

4. Move to appropriate repo that was created by createrepo earlier (see createrepo docs)

mv rpm_archives/bncsutil-1.4.1-Centos7.rpm .createrepo-centos7/

5. Update repo metadata

createrepo --update ./.createrepo-centos7/

6. Add your repo on the target machine

yum -y install yum-utils
yum-config-manager --add-repo https://centos7.rpm.xpam.pl
yum-config-manager --enable https://centos7.rpm.xpam.pl
rpm --import https://centos7.rpm.xpam.pl/xpam.pl-pubkey.asc

Since createrepo is pretty much just an http server you can simply delete an rpm and update the metadata in case things go south.

Repeat for Centos 6 etc.

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