Scribbles for my bad memory

在 Linux 系统上，/var/log/journal 目录通常用来存储系统日志。如果这个目录占用了过多的空间，可以通过以下几种方法来管理和限制日志的大小：

1. 修改 journald 配置

你可以通过修改 journald 的配置文件来设置日志的最大大小和保留时间：

1. 打开终端。

2. 编辑 journald 配置文件：

   sudo nano /etc/systemd/journald.conf
   

3. 在文件中添加或修改以下配置项：

   [Journal]
   SystemMaxUse=500M
   SystemKeepFree=100M
   SystemMaxFileSize=50M
   SystemMaxFiles=10
   

   这些选项的含义如下：

   • SystemMaxUse：限制日志的总大小。
   • SystemKeepFree：保留的磁盘空间。
   • SystemMaxFileSize：每个日志文件的最大大小。
   • SystemMaxFiles：最大日志文件数。

4. 保存文件并退出编辑器。

5. 重新启动 journald 服务以应用更改：

   sudo systemctl restart systemd-journald
   

2. 清理现有日志

如果你想立即释放一些空间，可以手动清理旧的日志文件：

sudo journalctl --vacuum-size=500M

这条命令会将日志文件的总大小限制在 500MB。

3. 定期清理日志

你可以使用 cron 任务来定期清理日志。例如，可以设置一个每天执行的任务来保持日志的大小在一个合理的范围内。

1. 打开 cron 编辑器：

   crontab -e
   

2. 添加以下行以每天清理日志：

   0 0 * * * /usr/bin/journalctl --vacuum-time=7d
   

   这样设置后，系统将每天清理超过 7 天的日志。

Running a small VPS with limited memory can be frustrating, especially when processes get killed due to low memory. A quick and easy way to help prevent this is by setting up a swap file.

This script will

1. Checks if swap already exists on the remote machine.
2. If not, it creates a 2GB swap file and enables it.
3. Adds the swap file to /etc/fstab to make it permanent.

The script uses scp to copy a temporary script to the remote machine and ssh to execute it. Here’s the full script:

#!/bin/bash

# Check if machine name is provided
if [ -z "$1" ]; then
  echo "Usage: $0 <machine-name>"
  exit 1
fi

REMOTE_MACHINE=$1
SWAPFILE=/swapfile
SIZE=2048

# Generate remote script content
REMOTE_SCRIPT=$(cat <<EOF
#!/bin/bash
if swapon --show | grep -q "$SWAPFILE"; then
  echo "Swap is already enabled on $SWAPFILE"
  exit 0
fi

sudo dd if=/dev/zero of=$SWAPFILE bs=1M count=$SIZE
sudo chmod 600 $SWAPFILE
sudo mkswap $SWAPFILE
sudo swapon $SWAPFILE

if ! grep -q "$SWAPFILE" /etc/fstab; then
  echo "$SWAPFILE none swap sw 0 0" | sudo tee -a /etc/fstab
fi
free -h
EOF
)

# Save remote script locally
echo "$REMOTE_SCRIPT" > /tmp/create_swap.sh

# Copy script to remote machine and execute it
scp /tmp/create_swap.sh $REMOTE_MACHINE:/tmp/
ssh $REMOTE_MACHINE "bash /tmp/create_swap.sh"

# Cleanup
ssh $REMOTE_MACHINE "rm /tmp/create_swap.sh"

How It Works

• The script checks if the swap file already exists by running swapon --show on the remote machine.
• If swap is already enabled, it exits.
• Otherwise, it creates a 2GB swap file (/swapfile), sets the right permissions, and adds it to /etc/fstab so it’s automatically enabled after a reboot.

Usage

1. Save the script as create_swap.sh and make it executable:

   chmod +x create_swap.sh
   

2. Run the script with the remote machine name:

   ./create_swap.sh <remote-machine>
   

And that's it! The script takes care of everything for you, ensuring your VPS has a swap file ready to handle memory spikes.

ENV DOTNET_SYSTEM_GLOBALIZATION_INVARIANT false
RUN apk add --no-cache icu-libs tzdata

Reference

By the way, my devops colleague told me if you can, changing the windows time zone id with its standard equivalent is the more preferred way. He said "its not good to set that environment variable to false"

In the realm of modern web development, the HTTPS protocol stands as a cornerstone of security. While Let's Encrypt provides SSL certificates at no cost, their certificate chains don't always play well with older Android versions, such as Android 5. This guide delves into the art of generating Android 5-compatible certificates and automating their renewal.

Step 1: Install Certbot and Nginx

Before embarking on this quest, ensure that your Ubuntu host has Certbot and Nginx installed.

sudo apt-get update
sudo apt-get install certbot nginx

Step 2: Download ISRG Root X1 Certificate

From the Let's Encrypt website, procure the latest ISRG Root X1 certificate and store it in a designated directory.

sudo wget -O /etc/letsencrypt/isrgrootx1.pem https://letsencrypt.org/certs/isrgrootx1.pem

Step 3: Craft the Automation Script

Forge a script named "update-certificates.sh" that automatically generates an Android 5-compatible certificate chain and reloads Nginx's configuration whenever Certbot renews the certificate.

#!/bin/bash

DOMAIN="yourdomain.com" 
CERT_DIR="/etc/letsencrypt/live/$DOMAIN"
FULLCHAIN="$CERT_DIR/fullchain.pem"
PRIVKEY="$CERT_DIR/privkey.pem"
ANDROID_FULLCHAIN="$CERT_DIR/fullchain-android.pem"
ISRG_ROOT="/etc/letsencrypt/isrgrootx1.pem"

# Generate Android5-compatible certificate chain
sudo cat $FULLCHAIN $ISRG_ROOT | sudo tee $ANDROID_FULLCHAIN > /dev/null

# Reload Nginx configuration
sudo systemctl reload nginx

Remember to replace "yourdomain.com" with your actual domain name and verify the paths are correct.

Step 4: Grant Script Execution Privileges

sudo chmod +x /path/to/update-certificates.sh

Step 5: Configure Certbot Renewal Hook

Certbot allows running custom hook scripts upon certificate renewal. Configure the aforementioned script as Certbot's "--deploy-hook" hook.

Edit Certbot's renewal configuration file (usually located at /etc/letsencrypt/renewal/yourdomain.com.conf):

renew_hook = /path/to/update-certificates.sh

Alternatively, configure it using Certbot's command-line option:

sudo certbot renew --deploy-hook /path/to/update-certificates.sh

Step 6: Set Up Automatic Renewal

Certbot by default sets up a cron job or systemd timer to automatically renew certificates. Verify this using the following command:

sudo systemctl list-timers | grep certbot

If no automatic renewal task exists, add a cron job manually:

sudo crontab -e

In the crontab file, add the following line to perform a renewal check daily:

0 2 * * * /usr/bin/certbot renew --deploy-hook /path/to/update-certificates.sh

Conclusion

By following these steps, you can ensure that HTTPS certificates generated using Let's Encrypt are compatible with Android 5 and automate certificate renewal. This eliminates the need to manually renew certificates every three months, significantly streamlining website maintenance.

English version

文言文，雅文也。余心向往之，故尝试以文言述此篇，若令君不悦，尚请原谅。

叙言

现代之网站开发,使用HTTPS协定,甚关键。Let's Encrypt所赐之SSL证书虽免费,然其证书链,不尽兼容旧安卓版本,如Android5。本文叙及生成兼容Android5证书之法,及自动续期之道。

第一步:安装Certbot及Nginx

先须确保汝主机上安装有Certbot及Nginx。

sudo apt-get update
sudo apt-get install certbot nginx

第二步:下载ISRG Root X1证书

自Let's Encrypt网站下载最新之ISRG Root X1证书,贮于指定之目录。

sudo wget -O /etc/letsencrypt/isrgrootx1.pem https://letsencrypt.org/certs/isrgrootx1.pem

第三步:编写自动化符

创一脚本名"update-certificates.sh",每当Certbot续证书后,自动生成兼容Android5证书链,并重新加载Nginx之配置。

#!/bin/bash

DOMAIN="yourdomain.com" 
CERT_DIR="/etc/letsencrypt/live/$DOMAIN"
FULLCHAIN="$CERT_DIR/fullchain.pem"
PRIVKEY="$CERT_DIR/privkey.pem"
ANDROID_FULLCHAIN="$CERT_DIR/fullchain-android.pem"
ISRG_ROOT="/etc/letsencrypt/isrgrootx1.pem"

# 生成兼容Android5证书链
sudo cat $FULLCHAIN $ISRG_ROOT | sudo tee $ANDROID_FULLCHAIN > /dev/null

# 重新加载Nginx之配置
sudo systemctl reload nginx

切记将DOMAIN替换为汝之实际域名,确保路径正确。

第四步:赐予脚本执行权

sudo chmod +x /path/to/update-certificates.sh

第五步:配置Certbot续订钩子

Certbot支持于续订证书后运行自定义钩子脚本。将上脚本配置为Certbot之"--deploy-hook"钩子。

编辑Certbot之续订配置文件(通常在/etc/letsencrypt/renewal/yourdomain.com.conf):

renew_hook = /path/to/update-certificates.sh

或使用Certbot之命令行选项配置:

sudo certbot renew --deploy-hook /path/to/update-certificates.sh

第六步:设置自动续订

Certbot默将配置一cron作业或systemd timer以自动续订证书。可通过以下命令确认:

sudo systemctl list-timers | grep certbot

若无自动续订任务,可手动添加一cron作业:

sudo crontab -e

于crontab文件中添加以下行,每日运行续订检查:

0 2 * * * /usr/bin/certbot renew --deploy-hook /path/to/update-certificates.sh

总结

经上述步骤,可确保使用Let's Encrypt所生之HTTPS证书兼容Android5,并实现证书之自动续订。如是,则无需每三月手动更新一次证书,大大简化了网站之维护工作。