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Manually expand partition scripts

· 2 min read

find partition for /​

findmnt -nosource /

/dev/sda3

split disk and partition number​

growpart /dev/sda 3

resize2fs​

resize2fs /dev/sda3

Automatically expand partiton mounted /

1. write go code​

package main

import (
    "os"
    "os/exec"
    "strings"
)

func main() {
    if os.Geteuid() != 0 {
        // fmt.Println("This script must be run as root")
        os.Exit(1)
    }

    // Identify the device that / is mounted on
    out, err := exec.Command("df", "/").Output()
    if err != nil {
        // fmt.Println("Error running df command:", err)
        os.Exit(1)
    }

    // Parse the output to get the device
    lines := strings.Split(string(out), "\n")
    if len(lines) < 2 {
        // fmt.Println("Unexpected output from df command")
        os.Exit(1)
    }

    fields := strings.Fields(lines[1])
    if len(fields) < 1 {
        // fmt.Println("Unexpected output from df command")
        os.Exit(1)
    }

    device := fields[0]
    // fmt.Println("Device:", device)

    // Extract the base device and partition number
    var baseDevice, partNum string
    if strings.HasPrefix(device, "/dev/mapper/") {
        baseDevice = strings.TrimSuffix(device, "1")
        partNum = "1"
    } else {
        baseDevice = strings.TrimRightFunc(device, func(r rune) bool {
            return r >= '0' && r <= '9'
        })
        partNum = strings.TrimPrefix(device, baseDevice)
    
    }

    // Grow the partition
    if err := exec.Command("growpart", baseDevice, partNum).Run(); err != nil {
        // fmt.Println("Error running growpart command:", err)
        os.Exit(1)
    }

    // Resize the filesystem
    if err := exec.Command("resize2fs", device).Run(); err != nil {
        // fmt.Println("Error running resize2fs command:", err)
        os.Exit(1)
    }
}

2. build​

go mod init expand_disk
go mod tidy

GOOS=linux GOARCH=amd64 go build .

3. write system service expand_disk.service​

[Unit]
Description=Expand disk partition mounted on /
After=initrd-usr-fs.target

[Service]
ExecStart=/usr/local/bin/expand_disk

[Install]
WantedBy=multi-user.target

4. enable service​

  • Install to system
sudo cp expand_disk.service /usr/lib/system/systemd/
  • Enable system 
sudo systemctl enable expand_disk