ChromeOS下Bash脚本if-elif-else逻辑失效，rootfs验证检测异常求助

Let's break down what's wrong with your original script logic and implement a cleaner, reliable solution that properly handles the rootfs verification case.

Problem Analysis: Flawed Original Logic #

Your initial if-elif-else structure is mutually exclusive, which creates a critical gap:

• When / is mounted read-only, the first if runs the mount command—but whether that mount succeeds or fails, the script skips the elif branch entirely (since the if condition was true). It then proceeds to execute the rest of your code, never hitting the error prompt.
• If / starts as read-write, the mount.out file doesn't exist at all, so the elif's grep command throws an invisible error and fails to trigger the message.

This is why you saw the script chug along until it hit Read-only file system errors—it never entered the error-handling path when the remount failed due to active rootfs verification.

Elegant Solutions: Check Mount Status Properly #

We can ditch the redundant mount.out file and directly verify the remount success using either command exit status or a recheck of the actual mount state.

Solution 1: Use mount Command Exit Status #

This is the most straightforward approach—rely on the command's built-in success/failure signal:

# ChromeOS's Specific!!!
rootfs="/dev/root"  # Ensure this variable is defined earlier in your script

# Check if / is mounted read-only
if grep -q "${rootfs}.*ro," /proc/mounts; then
    # Attempt to remount as read-write
    if ! mount -o remount,rw /; then
        # Remount failed—rootfs verification is still enabled
        echo -e "\nRootfs verification for the root partition must be removed to remount / as read-write."
        echo "To fix this, run the following command and reboot your system:"
        echo "sudo /usr/share/vboot/bin/make_dev_ssd.sh --remove_rootfs_verification --partitions 4"
        exit 1
    fi
fi

• grep -q runs silently, avoiding unnecessary output clutter.
• ! mount ... checks if the remount command failed directly, no temp files needed.
• The error message is clear and actionable for ChromeOS users.

Solution 2: Recheck Mount State (More Robust) #

If you want to be extra sure (in case edge cases affect the mount command's exit status), recheck /proc/mounts after the attempt:

# ChromeOS's Specific!!!
rootfs="/dev/root"

if grep -q "${rootfs}.*ro," /proc/mounts; then
    # Attempt remount, discard output
    mount -o remount,rw / &>/dev/null
    # Verify if the mount actually switched to read-write
    if grep -q "${rootfs}.*ro," /proc/mounts; then
        echo -e "\nRootfs verification is still enabled—cannot remount / as read-write."
        echo "Run this command and reboot to disable it:"
        echo "sudo /usr/share/vboot/bin/make_dev_ssd.sh --remove_rootfs_verification --partitions 4"
        exit 1
    fi
fi

This approach ignores the mount command's output and only cares about the actual current state of the filesystem, making it resilient to any unexpected command behavior.

Why Your Temporary Nested if Worked #

Your quick fix with nested if statements was actually on the right track—it checked the remount result immediately after running the command. The solutions above just refine that logic to be cleaner, more reliable, and avoid relying on temporary files.

Extra Tips for Your Script #

• Always quote variables like "${rootfs}" to avoid issues if the variable ever contains special characters.
• Use echo -e to handle newline characters reliably (single-quoted '\n' doesn't work in all shell environments).
• Before writing to /etc/env.d/30kvm later in your script, add a quick check to confirm / is read-write—this prevents unexpected "Read-only file system" errors even if something slips through the initial check.

内容的提问来源于stack exchange，提问作者mailman