Solution:

mdadm --detail --scan /dev/md127 >> /etc/mdadm/mdadm.conf

vim /etc/mdadm/mdadm.conf, edit the appended line to look like this:

ARRAY /dev/md0 metadata=1.2 UUID=XXXXXXXX:XXXXXXXX:XXXXXXXX:XXXXXXXX

In other words, remove the name part, and set the device to /dev/md0.

update-initramfs -u

reboot

Original post

dd if=/dev/zero of=test.file bs=64k count=16k conv=fdatasync

List zones:

timedatectl list-timezones

Set timezone:
timedatectl set-timezone Europe/Kyiv

sshfs -o allow_other username@some_server_ip:/home/user/specific/folder/ /mnt/some/folder

yum -y install python-pip; pip install --upgrade pip; pip install ngxtop
once done, it can be used via alias
alias nf='ngxtop -l /var/log/nginx/access.log top remote_addr http_referer'

set global net_buffer_length=1000000;
set global max_allowed_packet=1000000000;
SET foreign_key_checks = 0;

Once it done:

SET foreign_key_checks = 1;

imapsync --no-modules_version --tls1 --host1 source_server_name_or_ip --user1 source@user.name --password1 'some_password_for_source_user' --host2 target_server_name_or_ip --user2 target@user.name --password2 'some_password_for_target_user'

To delete all emails:
mailq | awk '{print$7}'|sed '/^$/d'|sed 's/>//g'|sort -n|uniq -c|sort -n|tail -10

To check specific email:
postcat -q email_id_here|less

perl -p -i -e 's/old/new/g'

Drop all cache:
ipconfig /flushdns

Check the records present/cached:
ipconfig /displaydns