mysql slave read only


Make sure you are working on slave server:

SHOW SLAVE STATUS \G ;
Slave_IO_Running: Yes
Slave_SQL_Running: Yes

SELECT @@global.read_only, @@global.super_read_only;
+--------------------+--------------------------+
| @@global.read_only | @@global.super_read_only |
+--------------------+--------------------------+
| 0 | 0 |
+--------------------+--------------------------+
1 row in set (0.00 sec)

SET GLOBAL super_read_only = 1;

SELECT @@global.read_only, @@global.super_read_only;
+--------------------+--------------------------+
| @@global.read_only | @@global.super_read_only |
+--------------------+--------------------------+
| 1 | 1 |
+--------------------+--------------------------+
1 row in set (0.00 sec)

Save config settings:
super_read_only = On

mysql> INSERT INTO authors (id,name,email) VALUES(1,"Test","test@test.com");
ERROR 1290 (HY000): The MySQL server is running with the --super-read-only option so it cannot execute this statement

If ERROR 1193 (HY000): Unknown system variable 'super_read_only'
SET GLOBAL read_only = 1;
UPDATE mysql.user SET super_priv='N' WHERE user<>'root';
FLUSH PRIVILEGES;

select user,host,plugin,Super_priv from mysql.user;
+------------------+-----------+-------------+------------+
| user | host | plugin | Super_priv |
+------------------+-----------+-------------+------------+
| root | localhost | unix_socket | Y |
| replica_user | % | | N |

ubuntu gcloud

apt install apt-transport-https ca-certificates gnupg -y
echo "deb [signed-by=/usr/share/keyrings/cloud.google.gpg] https://packages.cloud.google.com/apt cloud-sdk main" | tee -a /etc/apt/sources.list.d/google-cloud-sdk.list
curl https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key --keyring /usr/share/keyrings/cloud.google.gpg add -

apt update
apt install google-cloud-sdk

gcloud init
Welcome! This command will take you through the configuration of gcloud.

Your current configuration has been set to: [default]

You can skip diagnostics next time by using the following flag:
gcloud init --skip-diagnostics

Network diagnostic detects and fixes local network connection issues.
Checking network connection...done.
Reachability Check passed.
Network diagnostic passed (1/1 checks passed).

You must log in to continue. Would you like to log in (Y/n)?

upgrade/downgrade mongo

systemctl stop mongod.service
apt update
apt install mongodb-org=3.6.8 mongodb-org-mongos=3.6.8 mongodb-org-server=3.6.8 mongodb-org-shell=3.6.8 mongodb-org-tools=3.6.8
systemctl start mongod.service

mongo
db.adminCommand( { setFeatureCompatibilityVersion: "3.6" } )
db.adminCommand( { getParameter: 1, featureCompatibilityVersion: 1 } )

vi /etc/apt/sources.list.d/mongodb-org-4.0.list
deb [arch=amd64] https://repo.mongodb.org/apt/ubuntu bionic/mongodb-org/4.0 multiverse
apt update mongodb*
apt upgrade

wtmp clear last 10

#include
#include

struct utmp foo;

main()
{
printf("%lu\n", sizeof foo);
return 0;
}

Perl:
$utmp_size = utmp_record_size_goes_here;
$wtmp_file = "wtmp filename goes here";
open WTMP, "+<", $wtmp_file or die "$wtmp_file: ", $!; seek WTMP, -10 * $utmp_size, 2; truncate WTMP, tell(WTMP); close WTMP;