Showing posts from May, 2019

Technical Note: Dell XPS 9370 dynamic brightness control

Recently while using Windows Pro 10, I notice that my XPS 9370 adapts its screen brightness according to contents displayed on it. When I view websites with bright color theme, XPS 9370 screen will display the website's content with its maximum brightness. However, when I view websites using dark color theme, my dell laptop screen will automatically lower its brightness accordingly. This adaptation is good because lowering display brightness helps reduce power consumption, as well as make our eyes comfortable. However, my Dell laptop often reacts too much to minor changes of contents' brightness. A huge recognizable brightness often happens even when there are minor changes to color themes. The problem turns worse when brightness incurs latency. I switch between windows of multiple applications often enough to find the brightness adaption and its latency annoying. I decided to turn off this feature. It turns out to be quite difficult to find a place to turn off this feature

Technical Memo: DynamicUser in systemd

Recently, I received a really interesting question from my customer. He found out in his file system two files (directories), which belong to an user that not in /etc/passwd . Specifically in Ubuntu Linux 18.04, these 2 files are /var/lib/private/systemd /var/lib/private/systemd/timesync These two files belong to a user named systemd-timesync with UID/GID in 62583 and this user does not belong to /etc/passwd . Traditionally, a Linux user does not always need to be in /etc/passwd because it can come from many remote sources, for example LDAP NIS / NIS+ server Windows Domain Controller Server ... All current users, both from /etc/passwd and remote sources, can be queried by getent command [1] $ getent passwd Unfortunately, Our systemd-timesync user does not appear in getent list A quick Google points to an article [2], written by systemd developer - Lennart Poettering , explaining about DynamicUser feature. It turns out that DynamicUser was introduced from sy