https://www.twiceweb.net/board/view/ent_bangtan/30
Wednesday, August 29, 2018
How to set up MySQL max connections
This shows current max connections for mysql.
mysql> show variables like 'max_connections';
This shows current used connections for now.
mysql> show status like 'Max_used_connections';
To check how many connections were aborted. If you see aborted connection, you might need to increase max connection settings.
mysql> show status like 'Aborted%';
To change max connections:
mysql> set global max_connections=300;
If you want permanent settings:
# vi /etc/my.cnf
[mysqld]
max_connections = 300
You need to restart to make the change of /etc/my.cnf to be effective.
service mysqld restart
and check it again:
mysql> show variables like 'max_connections';
https://www.twiceweb.net/board/view/software/12
how to use crontab [linux]
* listing current crontab:
crontab -l
* editing crontab:
crontab -e
* example (once every 1st day of month):
0 0 1 * * shell_command_here
* special strings:
string meaning
------ -------
@reboot Run once, at startup.
@yearly Run once a year, "0 0 1 1 *".
@annually (same as @yearly)
@monthly Run once a month, "0 0 1 * *".
@weekly Run once a week, "0 0 * * 0".
@daily Run once a day, "0 0 * * *".
@midnight (same as @daily)
@hourly Run once an hour, "0 * * * *".
------ -------
@reboot Run once, at startup.
@yearly Run once a year, "0 0 1 1 *".
@annually (same as @yearly)
@monthly Run once a month, "0 0 1 * *".
@weekly Run once a week, "0 0 * * 0".
@daily Run once a day, "0 0 * * *".
@midnight (same as @daily)
@hourly Run once an hour, "0 * * * *".
https://www.twiceweb.net/board/view/software/8
Vultr Tokyo sysbench performance benchmark result
vultr performance test result (Tokyo region)
1 vCPU@2.4GHz
1GB RAM
25GB SSD
1TB traffic
$5/month
sysbench CPU test : 298 events/s
sysbench memory : 2850MB/s
sysbench file I/O :
read: 21.77MB/s
write: 14.51MB/s
sysbench mysql
read-only : 455 transactions/s, 7289 queries/s
read-write : 149 transactions/s, 2988 queries/s
write-only : 280.89 transactions/s, 1685 queries/s
how to redirect HTTP to HTTPS on nginx
sudo vi /etc/nginx/sites-available/SITEDOMAIN
server {
listen 80 default_server;
listen [::]:80 default_server;
server_name _;
return 301 https://$host$request_uri;
}
The first listen statement is for HTTP port of IPv4.
The second listen statement if for HTTP port of IPv6.
You can redirect from specific domain name as following:
server_name example.com www.example.com
https://www.twiceweb.net/board/view/computer/22
how to check disk space usage or free disk space on Ubuntu
$ df -h
the result:
Filesystem Size Used Avail Use% Mounted on
udev 464M 0 464M 0% /dev
tmpfs 99M 664K 98M 1% /run
/dev/vda1 25G 4.9G 19G 21% /
udev 464M 0 464M 0% /dev
tmpfs 99M 664K 98M 1% /run
/dev/vda1 25G 4.9G 19G 21% /
https://www.twiceweb.net/board/view/computer/20
how to check ubuntu free memory
$ free -m
you see like the following:
total used free shared buff/cache available
Mem: 985 661 191 1 132 185
Swap: 0 0 0
Mem: 985 661 191 1 132 185
Swap: 0 0 0
If you want memory usage and CPU consumption of each process:
$ top
or
$ htop
htop highlights information with color texts.
How to change timezone on Ubuntu 18.x
Check current timezone
$ timedatectl
Show available timezones
$ timedatectl list-timezone
Change timezone
$ sudo timedatectl set-timezone Asia/Seoul
how to use ubuntu firewall (ufw) 우분투 방화벽 ufw사용하는 법
Warning: If you enable ufw, then the default rule might block everything including your remote terminal connection.
기본 규칙 확인하기
check the default rule
$ cat /etc/default/ufw
ufw상태확인
check ufw status :
$ sudo ufw status verbose
기본정책 설정하기 : 기본적으로 들어오는 패킷은 모두 막고, 서버에서 나가는 패킷은 모두 허용합니다.
set up default policies
$ sudo ufw default deny incoming
$ sudo ufw default allow outgoing
SSH연결 허용하기 (필수. 이 규칙이 없으면 원격터미널연결이 불가능해집니다.)
allow SSH connections (you need this rule to connect to your server via remote terminal program)
$ sudo ufw allow ssh
or allow port 22 (default ssh port = 22)
$ sudo ufw allow 22
UFW켜기
enable UFW
$ sudo ufw enable
UFW상태 확인
check ufw status
$ sudo ufw status verbose
HTTP허용하기
allow HTTP (if you need)
$ sudo ufw allow http
or
$ sudo ufw allow 80
HTTPS허용하기
allow HTTPS (if you need)
$ sudo ufw allow https
or
$ sudo ufw allow 443
포트범위 허용하기
allow specific port ranges (ex. 3000~3003 TCP port)
$ sudo ufw allow 3000:3003/tcp
IP주소 허용하기
allow specific IP address
$ sudo ufw allow from 11.12.13.14
IP & port allow rule:
$ sudo ufw allow from 11.12.13.14 to any port 22
서브넷 허용하기
allow subnets (ex. 11.12.13.1 ~ 11.12.13.254)
$ sudo ufw allow from 11.12.13.0/24
연결 막기
deny connections
$ sudo ufw deny ftp
or deny port 21
$ sudo ufw deny 21
or deny ip address
$ sudo ufw deny from 11.12.13.14
방화벽규칙번호 확인
list firewall rule number
$ sudo ufw status numbered
번호로 방화벽규칙 삭제
delete ufw rule by rule number (ex. delete ufw rule number 2)
$ sudo ufw delete 2
내용으로 방화벽규칙 삭제
delete ufw rule by actual rule
$ sudo ufw delete allow http
UFW방화벽 끄기
disable UFW firewall
$ sudo ufw disable
Vultr Tokyo sysbench performance benchmark result
vultr performance test result (Tokyo region)
1 vCPU@2.4GHz
1GB RAM
25GB SSD
1TB traffic
$5/month
sysbench CPU test : 298 events/s
sysbench memory : 2850MB/s
sysbench file I/O :
read: 21.77MB/s
write: 14.51MB/s
sysbench mysql
read-only : 455 transactions/s, 7289 queries/s
read-write : 149 transactions/s, 2988 queries/s
write-only : 280.89 transactions/s, 1685 queries/s
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