dimus's questions

When I run this query on a dataset

zfs list -d 1 -t all -o name,used,refer,written,compressratio sfg-backup/mx

I see the following stats:

zfs list -d 1 -t all -o name,used,refer,written,compressratio sfg-backup/mx
NAME                                           USED     REFER  WRITTEN  RATIO
sfg-backup/mx                                  300G      276G        0  1.80x
sfg-backup/mx@madcow_2023-04-15_23:15:00_UTC  4.04G      275G     275G  1.28x
...
sfg-backup/mx@madcow_2023-04-21_01:15:00_UTC     0B      276G        0  1.28x
sfg-backup/mx@madcow_2023-04-21_02:15:00_UTC     0B      276G    4.26G  1.28x
sfg-backup/mx@madcow_2023-04-21_03:15:00_UTC     0B      276G        0  1.28x

However, when I run a backup, that has the last snapshot as madcow_2023-04-21_01:15:00_UTC the size of the backup is not 4.26GB but 31.4GB

syncoid --no-sync-snap 10.0.1.2:sfg-backup/mx work/sfg/mx
NEWEST SNAPSHOT: madcow_2023-04-21_03:15:00_UTC
Sending incremental sfg-backup/mx@madcow_2023-04-21_01:15:00_UTC ... madcow_2023-04-21_03:15:00_UTC (~ 31.4 GB):
31.5GiB 0:03:16 [ 163MiB/s] [==================================================================================================>] 100%

adding -c for compression brings the size to 4.3G (these are slighly different snapshots, but with more of less the same content.

zfs send -nv -c -I sfg-backup/mx@madcow\_2023-04-24\_00:15:00\_UTC sfg-backup/mx@madcow\_2023-04-24\_03:15:00\_UTC
send from @madcow_2023-04-24_00:15:00_UTC to sfg-backup/mx@madcow_2023-04-24_01:15:00_UTC estimated size is 215M
send from @madcow_2023-04-24_01:15:00_UTC to sfg-backup/mx@madcow_2023-04-24_02:15:00_UTC estimated size is 4.09G
send from @madcow_2023-04-24_02:15:00_UTC to sfg-backup/mx@madcow_2023-04-24_03:15:00_UTC estimated size is 624B
total estimated size is 4.30G

# without -c flag:
zfs send -nv  -I sfg-backup/mx@madcow\_2023-04-24\_00:15:00\_UTC sfg-backup/mx@madcow\_2023-04-24\_03:15:00\_UTC
send from @madcow_2023-04-24_00:15:00_UTC to sfg-backup/mx@madcow_2023-04-24_01:15:00_UTC estimated size is 216M
send from @madcow_2023-04-24_01:15:00_UTC to sfg-backup/mx@madcow_2023-04-24_02:15:00_UTC estimated size is 31.3G
send from @madcow_2023-04-24_02:15:00_UTC to sfg-backup/mx@madcow_2023-04-24_03:15:00_UTC estimated size is 624B
total estimated size is 31.5G

Can you help me understand what can cause this large discrepancy in sizes? Why reported by ZFS compression is 1.28 and transfer compression is 31.5/4.3=7.3?

I run mysql container using Docker. I start it with like

sudo docker -d --name mysql -p 3306:3306 -v /var/lib/mysql:/var/lib/mysql mysql_image 

I suspect that stopping mysql by stopping docker is not safe. Am I wrong?

sudo docker stop mysql

Is it safer to stop mysql inside of the container first?

sudo docker exec mysql /usr/bin/mysqladmin shutdown

I happened to be in a situation where I am in charge for 100+ systems on top of my job as a programmer. Everything we run is Linux (Debian, Ubuntu, Centos) and gladly our sysadmin set everything with chef, so security patches can be applied quickly.

I would like to know how can I follow newly discovered vulnerabilities spending least amount of time.

As a programmer I am a fan of Gemnasium, which does this kind of job for ruby gems I use in my projects.

Do you know if it is possible to use Nginx with Shibboleth?