How to umount on a closed distro

[ebolisa]

Hi,

I'm running an old motioneye distro on a Raspberry Pi with python 2.7. It's working fine but it has filenames read-write only.

Because I'd like to run a Python script which updates a log file, I'm not able to do automatically because of the locked filesystem.
If I issue os.system("mount -o remount,rw /") it works and I can update my log file accordingly.

So, I added @reboot mount -o remount,rw / in crontab but it doesn't work. rc.local and systemd are not available.

I also added the below code in my script but with no avail.

Is there another solution to my problem?

TIA

def write_to_log(message):
    if os.system("mount | grep 'on / ' | grep -q rw") == 0:
        with open("/home/log.txt", "a") as log_file:  # Open in append mode
            timestamp = datetime.now(local_tz).strftime("%Y-%m-%d %H:%M:%S")
            log_file.write("{} - {}\n".format(timestamp, message))
    else:
        os.system("mount -o remount,rw /")

[ndc85430]

Are you not able to change /etc/fstab to mount the filesystem as read-write?

[ebolisa]

Are you not able to change /etc/fstab to mount the filesystem as read-write?

Which of these files are you referring to?

-rw-r--r--    1 root     root           242 Oct 29  2021 fstab.disk
-rw-r--r--    1 root     root           228 Oct 29  2021 fstab.extra
-rw-r--r--    1 root     root           506 Oct 29  2021 fstab.overlay
-rw-r--r--    1 root     root           523 Oct 29  2021 fstab.sys

I'm not really comfortable in modifying any of those files.

[ndc85430]

Normally on Linux, there's just one file called fstab in /etc. I can't advise further here - I don't know the Raspberry Pi system and whether those files are in the normal fstab format. You might want to ask on a Raspberry Pi forum about that.

[Skaperen]

this is not a Python question. it is more of a Raspberry Pi or Linux distro variation question. perhaps you can try linuxquestions.org to see what they may know. you may be asked to list all the files in your /etc directory.

[DeaD_EyE]

def write_to_log(message):
    if os.system("mount | grep 'on / ' | grep -q rw") == 0:
        with open("/home/log.txt", "a") as log_file:  # Open in append mode
            timestamp = datetime.now(local_tz).strftime("%Y-%m-%d %H:%M:%S")
            log_file.write("{} - {}\n".format(timestamp, message))
    else:
        os.system("mount -o remount,rw /")

Reminds me, the code I've written to put one CPU-Core to 100% load to speed up the CPU-fan. The problem were the regulators, which were too hot and degraded, but if the fan were speeded up, it didn't crash during rapid load changes. It worked one year until I changed my hardware.

You're trying to solve a possible hardware or OS-dependent issue with a bad written program. It's not a solution, it's a workaround, and you know that a workaround will stay forever.

Check your SD-Card for file system errors and degradation. Maybe the media itself is affected.
If the media is OK, then the issue should be the OS itself. Btw. I don't know the distribution you're using.

In the most cases, the issue is caused by a too early power off, if you shut down your RPi. If the RPi was not able to umount before the power off, it could corrupt the FS, which could prevent mount in readwrite mode if fsck could not repair it.

Never use Python 2.7 for new programs and never use os.system(). Even in C you should not use the function system(). The function subprocess.run() is a good replacement for os.system(). It returns an object which allows you to access stdout, stderr, returncode, etc.