Flush DNS on Mac


Making DNS changes and wanting to force a flush on a Mac?

Here are the commands for the different mac versions:

MacOS VersionCommand
macOS 12 (Monterey)sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
macOS 11 (Big Sur)sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
macOS 10.15 (Catalina)sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder
macOS 10.14 (Mojave)sudo killall -HUP mDNSResponder
macOS 10.13 (High Sierra)sudo killall -HUP mDNSResponder
macOS 10.12 (Sierra)sudo killall -HUP mDNSResponder
OS X 10.11 (El Capitan)sudo killall -HUP mDNSResponder
OS X 10.10 (Yosemite)sudo discoveryutil udnsflushcaches
OS X 10.9 (Mavericks)sudo killall -HUP mDNSResponder
OS X 10.8 (Mountain Lion)sudo killall -HUP mDNSResponder
Mac OS X 10.7 (Lion)sudo killall -HUP mDNSResponder
Mac OS X 10.6 (Snow Leopard)sudo dscacheutil -flushcache
Mac OS X 10.5 (Leopard)sudo lookupd -flushcache
Mac OS X 10.4 (Tiger)lookupd -flushcache

Linux Kernel Tuning: task blocked for more than 120 seconds


One of the most viewed posts in 2022… I hope it helped resolving some linux performance issues…

Hernan Vivani's Blog

This might be old school, and maybe even boring reading. But, if you concern about performance on Linux servers, at some point, you will have to have a look to the kernel messages.

The problem:

When we run very stressful jobs running on large servers (large number of CPU’s and RAM memory), where IO activity is very high. It is pretty common to start seeing these messages on the ‘dmesg’ kernel output:

[24169.372862] INFO: task kswapd1:1140 blocked for more than 120 seconds.
[24169.375623] Tainted: G E 4.9.51-10.52.amzn1.x86_64 #1
[24169.378445] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[24169.382533] kswapd1 D 0 1140 2 0x00000000
[24169.385066] ffff8811605c5a00 0000000000000000 ffff8823645dc900 ffff882362844900
[24169.389208] ffff882371357c00 ffffc9001a13ba08 ffffffff8153896c ffffc9001a13ba18
[24169.393329] ffff881163ac92d8 ffff88115e87f400 ffff882362844900 ffff88115e87f46c
[24169.445313] Call Trace:
[24169.446981] [<ffffffff8153896c>] ? __schedule+0x23c/0x680
[24169.449454] [<ffffffff81538de6>] schedule+0x36/0x80
[24169.451790] [<ffffffff8153907e>] schedule_preempt_disabled+0xe/0x10
[24169.454509] [<ffffffff8153a8d5>] __mutex_lock_slowpath+0x95/0x110
[24169.457156] [<ffffffff8153a967>] mutex_lock+0x17/0x27
[24169.459546] [<ffffffffa0966d00>] xfs_reclaim_inodes_ag+0x2b0/0x330 [xfs]
[24169.462407] [<ffffffffa0967be3>] xfs_reclaim_inodes_nr+0x33/0x40 [xfs]
[24169.465203] [<ffffffffa0978f59>] xfs_fs_free_cached_objects+0x19/0x20 [xfs]
...

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Christiaan Barnard y René Favaloro


Here is a memory of a time when we went to the Christiaan Barnard hospital (who performed the world’s first human-to-human heart transplant operation) in Cape Town, South Africa, where, I immediately remembered Rene Favaloro, the great Argentinian surgeon who invented the coronary artery bypass surgery.

Did you know both where contemporary?

Here is a photo I’ve found on the internet.

ChristiaanBarnard-RenéFavaloro
I feel a deep admiration for these two heart scientists…. they are inspiring leaders for new generations.


Here is a summary of 2019’s Google Doodle:

“‘We’ is more important than ‘I.’ 

In medicine, the advances are always the result of many efforts accumulated over the years,” wrote Dr. René Favaloro, the Argentinian surgeon who introduced coronary artery bypass surgery into clinical practice and is celebrated in today’s Doodle.

Born in the city of La Plata on this day in 1923, René Gerónimo Favaloro spent the first 12 years of his medical career as a country doctor in the farming community of Jacinto Arauz. He built an operating room, trained his own nurses, set up a local blood bank, and educated patients on how to prevent common ailments. The experience left him with a lifelong conviction that healthcare was a basic human right, regardless of economic circumstances.

In 1962, he traveled to the United States to practice at the Cleveland Clinic, where he worked alongside Mason Sones, a pioneer of cineangiography—the reading and interpreting of coronary and ventricular images. After studying angiograms in the Sones Library, Dr. Favalaro was convinced that coronary artery bypass grafting could be an effective therapy.

On May 9th, 1967, Dr. Favaloro operated on a 51-year-old woman with a blockage in her right coronary artery. Attaching her to a heart-lung machine, he stopped her heart and used a vein from her leg to redirect blood flow around the blockage. The historic operation was a success, and since then, the procedure has saved countless lives during the past half-century.

Returning to Argentina in the early 1970s, Dr. Favaloro established the Favalaro Foundation in Buenos Aires. The center serves patients based on their medical needs rather than their ability to pay and teaches Dr. Favaloro’s innovative techniques to doctors all over Latin America.

Hernan Vivani's Blog

Hoy fuimos al Christiaan Barnard Memorial Hospital, e inmediatamente me acordé de René Favaloro, pensando si esas dos eminencias de la cardiología serían contemporáneos…

Revolviendo en internet encontré esta foto.

ChristiaanBarnard-RenéFavaloro

Comparto una profunda admiración por estos dos científicos del corazón (en todo el sentido de la palabra).

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