Page 2 | Posts in category “Tutorial” | Scribbles for my bad memory

Posts in category “Tutorial”

移动介质上的Linux：使用 tmpfs、关闭 atime 以延长 SD 卡或优盘的使用寿命

我有一台老旧的 Asus C100P Chromebook，Google早在几年前就停止了对它的支持。它是32位ARM CPU，因此我没法替它更换BIOS，但我可以在developer mode下启用优盘启动，这样我就能够在优盘或者sd卡运行Linux。

然而，在使用 SD 卡或其他闪存设备作为操作系统存储时，合理管理写入操作至关重要。本文将介绍如何通过使用 tmpfs 文件系统、关闭 atime 来延长设备的使用寿命。

1. 使用 tmpfs

什么是 tmpfs？

tmpfs 是一种基于内存的临时文件系统,具有以下优点:

高速存储: 数据存储在内存中,读写速度极快。
动态大小: 根据实际使用情况动态分配内存,不会固定占用资源。
减少写入: 适合存储临时文件和日志,显著减少对闪存的写入操作。

如何配置 tmpfs

1.1 编辑 /etc/fstab 文件

打开终端并输入:

sudo nano /etc/fstab

添加以下行以创建 tmpfs 挂载点:

tmpfs /tmp tmpfs defaults,noatime,mode=1777 0 0
tmpfs /var/log tmpfs defaults,noatime,mode=0755 0 0

1.2 挂载 tmpfs

保存文件后,运行以下命令使更改生效:

sudo mount -a

1.3 验证挂载

使用以下命令确认 tmpfs 是否成功挂载:

df -h

您应该能看到类似于 /tmp 和 /var/log 的 tmpfs 挂载点。

1.4 设置自动复制日志到 tmpfs

为了在系统启动时自动将日志复制到 tmpfs,我们需要修改 /etc/rc.local 文件:

a. 创建一个目录来存储持久化的日志:

sudo mkdir -p /var/log.hdd
sudo cp -a /var/log/* /var/log.hdd/

b. 编辑 /etc/rc.local 文件:

sudo nano /etc/rc.local

c. 在文件中添加以下内容:

#!/bin/sh -e
# 复制日志文件到 tmpfs
cp -a /var/log.hdd/* /var/log/
exit 0

d. 确保 rc.local 文件具有执行权限:

sudo chmod +x /etc/rc.local

2. 关闭 atime

atime (访问时间) 是文件系统的一个属性,每次访问文件时都会更新。关闭 atime 可以减少不必要的写入操作,从而延长 SD 卡的寿命。

如何关闭 atime

2.1 编辑 /etc/fstab 文件

打开 /etc/fstab 文件:

sudo nano /etc/fstab

2.2 修改挂载选项

找到 SD 卡对应的挂载项(通常是根分区 /),在挂载选项中添加 noatime:

UUID=xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx / ext4 defaults,noatime 0 1

2.3 重新挂载文件系统

保存文件后,使用以下命令重新挂载文件系统:

sudo mount -o remount /

请记住,虽然这些方法可以有效延长 SD 卡的使用寿命，但仍然建议定期备份重要数据，以防意外发生。毕竟备份不做，十恶不赦！

又：

mode=1777 中的 1 表示设置了"粘滞位"(sticky bit)。具体含义如下:

777 部分:
- 7: 所有者(owner)有读、写、执行权限
- 7: 用户组(group)有读、写、执行权限
- 7: 其他用户(others)有读、写、执行权限
前面的 1:
- 表示设置了粘滞位(sticky bit)

粘滞位的作用:

对于目录,当设置了粘滞位时，只有文件的所有者、目录的所有者或 root 用户才能删除或重命名该目录中的文件。
这通常用于像 /tmp 这样的公共目录，允许所有用户创建文件,但防止用户删除或修改其他用户的文件。

所以 mode=1777 的含义是:

所有用户都可以在该目录中创建、读取和执行文件(777)
但只有文件所有者和目录所有者可以删除或重命名文件(1)

这种权限设置既保证了目录的共享性，又提供了一定的安全保护，防止用户互相干扰。

How to Enable User-Level Systemd Services to Start Automatically on Ubuntu After Reboot

TL;DR

If your user-level systemd service on Ubuntu doesn't start automatically after a reboot, enable it with systemctl --user enable HappyNotes.Api.service. If you encounter an error about an existing symlink, remove it first. To allow the service to run without an active user session, enable lingering using loginctl enable-linger <username>. Finally, ensure your service file has the correct [Install] section and reboot to check if the service starts as expected.

The Problem

After configuring a user-level service with systemd, you might find that it remains inactive after rebooting your server. For example, you may run the command:

systemctl --user status HappyNotes.Api.service

And see output indicating that the service is inactive (dead) and disabled.

Solution Steps

Enable the Service: First, ensure your service is enabled to start at boot:
```
systemctl --user enable HappyNotes.Api.service
```
If you encounter an error stating that the service is already linked, you may need to remove the existing symlink:
```
rm ~/.config/systemd/user/default.target.wants/HappyNotes.Api.service
```
Check for Linger: User-level services require an active user session to run. To allow your user services to run even when you're not logged in, enable lingering:
```
loginctl enable-linger $USER
```
Verify Service Configuration: Ensure your service file has the correct [Install] section:
```
[Install]
WantedBy=default.target
```
Reboot and Test: After enabling lingering and ensuring your service is set up correctly, reboot your server:
```
sudo reboot
```
After rebooting, check the status of your service again:
```
systemctl --user status HappyNotes.Api.service
```

By following these steps, you can ensure that your user-level systemd services start automatically after a reboot on Ubuntu. Enabling lingering is the key, which is particularly useful for server environments where continuous operation of services is desired.

Docker Volumes in Production: A Practical Guide to Named Volumes vs Bind Mounts

When working with Docker containers in production, understanding volume management is crucial. This guide will help you make informed decisions about when to use named volumes versus bind mounts (directory mapping).

TL;DR

Use named volumes for persistent data (databases, application state)
Use bind mounts for config files and development
Combine both in production for optimal setup

Understanding the Basics

Named Volumes

volumes:
  - postgres_data:/var/lib/postgresql/data

Docker manages these volumes internally. Think of them as "black boxes" that Docker handles for you.

Bind Mounts (Directory Mapping)

volumes:
  - ./config:/etc/app/config

You manage these directories directly on your host machine.

When to Use What?

Use Named Volumes For:

Database storage
Application state
Generated assets
Any data that needs persistence but not direct access

Benefits:

Managed by Docker
Better performance
Automatic permissions handling
Easier backups
Portable across environments
Built-in volume management commands

Use Bind Mounts For:

Configuration files
Static files during development
Source code in development
Any files you need to edit from host

Benefits:

Direct access from host
Easy to edit
Version control friendly
Quick updates without container restart
Shareable across environments

Real-World Example

Here's a typical production setup combining both approaches:

version: '3'
services:
  db:
    image: postgres:15
    volumes:
      # Data persistence with named volume
      - postgres_data:/var/lib/postgresql/data
      # Configuration with bind mounts
      - ./config/postgres.conf:/etc/postgresql/postgresql.conf:ro

  nginx:
    image: nginx
    volumes:
      # Config files with bind mounts
      - ./config/nginx/nginx.conf:/etc/nginx/nginx.conf:ro
      - ./config/nginx/conf.d:/etc/nginx/conf.d:ro
      # Static files with bind mount
      - ./static:/usr/share/nginx/html:ro

  app:
    image: node:18
    volumes:
      # Application data with named volume
      - app_data:/app/data
      # Config with bind mount
      - ./config/app.json:/app/config/app.json:ro

volumes:
  postgres_data:
  app_data:

Migration Tips

Moving from Bind Mounts to Named Volumes

If you're currently using bind mounts for data and want to switch to named volumes:

# Create new volume
docker volume create myapp_data

# Copy data
docker run --rm \
  -v /old/path:/source:ro \
  -v myapp_data:/destination \
  ubuntu \
  bash -c "cp -av /source/. /destination/"

Best Practices

Named Volumes
- Always use for persistent data
- Name them descriptively
- Regular backups
- Don't manipulate directly on host
Bind Mounts
- Use read-only (:ro) when possible
- Keep configs in version control
- Use relative paths for portability
- Store in a config/ directory
General
- Document your volume strategy
- Regular backups for both types
- Monitor disk usage
- Use clear naming conventions

Common Pitfalls to Avoid

Using bind mounts for database storage
Hardcoding absolute paths
Not setting proper permissions
Forgetting to backup named volumes
Direct manipulation of named volume directories

Conclusion

The key to successful Docker volume management is using the right tool for the job:

Named volumes for data that needs persistence
Bind mounts for configs and development
Combine both for a robust production setup

Remember: When in doubt, prefer named volumes for data and bind mounts for configuration.

Step 6 in detail: Configure Telegram Sync in HappyNotes

If you haven't read Step1 to Step 5, click Step 1 ~ Step 5

Open the HappyNotes App:
- Open https://happynotes.shukebeta.com with your favorite broswer and then navigate to the **Settings** page.
Access Telegram Sync Settings:
- Within the Settings page, look for the "Note Sync - Telegram" option.
- Tap on it to open the sync settings page.
Add a New Sync Configuration:
- On the sync settings page, click on the "+ Add" button to create a new sync configuration.
Enter the Required Information:
- Source Note Choose the appropriate source note to sync from the options provided (e.g., Public, Private, All, Tag).
  - All - for backup purpose. It will sync every new note to the channel you specified. (Please don't use a public channel if you have any private notes!!!)
  - Private - only sync private notes to specified channel, you definitely should not use a public channel for this type of notes!
  - Public - only sync public notes to specified channel - if you use a telegram channel for your blog or microblog purpose, this option is for you!
  - Tag - only sync notes that are tagged with specific tag, You must know that it does not check the private/public flag, every new note that has the specified tag will be sent to the specified channel.
- Channel Id: In the "Channel Id" field, enter the Channel Id you obtained earlier which looks like -100123456789.
- Channel Name: This is a remark for the channel id, you can use the same channel name on Telegram or anything else you want.
- Telegram Bot Token: In this field, paste your Telegram Bot Token . I strongly recommend you to use copy/paste feature instead of manually typing the token to avoid typos.
- **Token Remark: ** Just like the channel name, this Token Remark helps you remember which token you are using for this channel. You can use your bot's name or anything else you want.
Save the Configuration:
- After filling in the details, click the "Save" button to store your sync configuration.
Test the Sync Setting:
- Once saved, you'll see your new configuration listed on the sync settings page.
- Tap the "Test" button to send a test message to your Telegram channel.
- If the test is successful, you’ll receive a confirmation message in your Telegram channel indicating that the sync is working, and the Test button will disappear.
Activate or Adjust Sync Settings:
- You can Disable or Activate or Delete a setting based on your requirements.
- Make sure your bot is active and configured correctly to ensure smooth synchronization.

How to Sync Your Telegram Channel with HappyNotes

Happy Notes app recentlys supports to sync new notes to your specified telegram channel based on the rules you set. If you want to enjoy seamless note synchronization between your Telegram channel and the HappyNotes app, follow these easy steps:

Step 0: Find and Add @getidsbot

Open Telegram and search for @getidsbot.
Start a chat with the bot by clicking on "Start."

Step 1: Create Your Telegram Bot

Search for @BotFather in Telegram and start a conversation.
Use the /newbot command to create a new bot.
Follow the prompts to give your bot a name and username.
Note: The bot's username must end with "bot" (e.g., MySyncBot).

Step 2: Get Your Telegram Bot Token

After creating the bot, @BotFather will provide you with a token. This token is essential for integrating your bot with other services, so keep it safe.

Step 3: Add Your Bot to Your Telegram Channel as an Admin

Convenient Method:

Open the conversation with your newly created bot in Telegram.
Tap on the bot's icon in the top right corner.
Click on "Add to Group or Channel".
Select the channel you want to add the bot to, and it will automatically be added as an admin with the necessary permissions.

Alternative Method:

Go to your Telegram channel's settings.
Select "Administrators" and manually add your newly created bot as an admin.
Ensure the bot has the necessary permissions to send and manage messages.

Step 4: Manually Write the First Message to the Channel

Send a message to your channel as you usually would. This message is necessary to identify the channel ID later.

Step 5: Forward the Message to @getidsbot

Forward the message you just sent to @getidsbot.
The bot will reply with the channel ID. Keep this ID safe; you’ll need it for the next step.

Step 6: Configure Telegram Sync in HappyNotes

Open the HappyNotes app (https://happynotes.shukebeta.com) and navigate to the settings page.
Click/Tap Note Sync - Telegram to go to the Telegram Sync page
Add your bot’s token and the channel ID to the sync settings.

Step 7: Test the Setting

Use the "Test" option in HappyNotes to send a test message to your Telegram channel.
Ensure the message is successfully sent, confirming the integration is working.

Step 8: Enjoy Syncing Your Notes with Telegram!

With everything set up, your notes will now sync with your Telegram channel automatically.
You can now easily access your notes from within Telegram, making your workflow even smoother.