I have a rootfs boot image that I want to test by mounting on my local file system. How can I do this ?
EDIT: The file was a rootfs.img but it turned out I did not have the correct filesystem support in my custom kernel. pjz's answer works once the fs support is there.
Need more info - what kind of image is it?
is it a file that's a filesystem? if so you mount it like:
mount -o loop rootfs.img /mnt/rootfs
if it's a subdir of your filesystem that you'r exporting via nfs, you can simulat ethe environment you've created by chrooting to it:
chroot /path/to/nfs/rootdir/
Related
I need to check some data in linux kernel while mounting NTFS, but if I use
mkfs.ntfs
or
mkntfs
and then
mount -t ntfs ...
The string containing info about file system in kernel is "fuseblk", not "ntfs" that i need.
Maybe that's because of "ntfs-3g" packs that i installed, as i know it contains fuse drivers.
How to mount NTFS without fuse?
I tried to change options in "mount" or "mkfs", but nothing helped.
I just deleted ntfs-3g packages and it worked as i wanted... Stranger things.
I'm using Yocto on Ubuntu 18.04 with the Warrior Branch of Meta-Tegra in order to try to integrate the RAUC Open Source project for Linux Firmware Updates.
I've learned that U-Boot has issues writing to EXT4 partitions ( to update the U-Boot Env ) if the EXT4 filesystem it is writing to has the metadata_csum attribute. Linux cannot mount the Root Filesystem if that attribute is enabled and U-Boot writes at all to it.
Here are some posts on that:
https://patchwork.ozlabs.org/patch/818337/
http://u-boot.10912.n7.nabble.com/PATCH-1-1-fs-ext4-do-not-write-on-filesystem-with-metadata-csum-feature-td362715.html
I proved that this is the case by mounting the resulting SDCARD image from Yocto on Ubuntu and running the following command to disable metadata_csum:
sudo tune2fs -O ^metadata_csum /dev/sdb1
tune2fs 1.44.1 (24-Mar-2018)
Disabling checksums could take some time.
Proceed anyway (or wait 5 seconds to proceed) ? (y,N) y
After running that command - U-Boot can read/write at will from U-Boot space and Linux can mount the Root File System.
I am trying to figure out how to disable the checksums with Tune2fs on Ubuntu at image creation time with Yocto. Where/How can I add this so that the image has checksums disabled at image creation time from Yocto?
I briefly looked over meta-tegra and I think it uses the ext4 root filesystem image created through image_class.bcclass. You can add parameters to the mkfs.ext4 thorugh EXTRA_IMAGECMD. It should be possible to just create the filesystem with metadata_csum disabled, instead of turning it off later.
Try
EXTRA_IMAGECMD_append = " -O ^metadata_csum"
in your local.conf
I have an embedded board which I am running Linux on it. Linux is booted via uboot. The full Linux image is build as Initramfs. When the system is booted I find that the root FS is read write. My understanding is that the Initramfs should be by default read only. Right?
I have tried to change boot parameter in uboot as well to have it read only, but it had no effect. I wonder what to do to make the Initramfs read only by default?
The full Linux image is build as Initramfs.
That's a poorly worded, if not inaccurate, description.
An initramfs uses a cpio archive file, which is not an image file.
The cpio archive file can be linked into the Linux kernel image.
An initramfs "image" is always a cpio archive file, and not a filesystem image.
My understanding is that the Initramfs should be by default read only. Right?
Wrong.
It makes no sense to mount the initramfs as a read-only filesystem.
When the initramfs is created and mounted, it's an empty filesystem.
If it was mounted read-only, then the initramfs could not be populated with its cpio archive, and the initramfs would remain an empty filesystem.
The suggestion to use a kernel command line parameter such as root=/dev/ram ro indicates a confusion between (deprecated) ramdisk and ramfs.
See Linux kernel Documentation/filesystems/ramfs-rootfs-initramfs.txt
I wonder what to do to make the Initramfs read only by default?
You can remount it to be read-only.
See http://lkml.iu.edu/hypermail/linux/kernel/0908.1/01693.html
and
https://serverfault.com/questions/463828/linux-initramfs-read-only
How to replace the contents of rootfs partition while the device is booted up?
I am using pine64 (1GB) with stripped debian version and struck in writing a factory reset script which will replace all files in the rootfs partition while the device is running? resident restore file could be tar or img file.
I have already tried two approaches
dd the partition from image to the partition on device.
sudo dd if=pine-debian.img skip=*start of rootfs partition* seek=*start of rootfs partition* of=/dev/mmcblk0
Extract the compressed content to the / directory.
sudo tar -C / -zxvf pine-debian.tar.gz
After both the approaches, the system can recognize any command, not even ls. Any help will be appreciated about how to solve this. how to replace fs content while the device is running?
Ideally, you should have two partitions each with a copy of the rootfs. You can write the partition that is currently not in use with dd, and then update the bootloader configuration to point to the just written partition as the root. swupdate supports such a dual-bank scenario, but it only has native support for U-Boot; if you use a different bootloader, you'll have to add a script to perform the swap.
If you really need to overwrite in-place, directly overwriting the partition is not possible because that filesystem is currently in use. Untarring will also fail because some files are currently in use - in particular libc. You could try to add the --unlink-first option to the untar command, but I'm not sure if that works.
Two other options:
Instead of overwriting the full rootfs, use Debian package upgrades. They have pre- and post-install scripts to make the upgrade safe.
Swap to a (temporary, small) in-RAM root filesystem to perform the upgrade. This root filesystem should just contain busybox and the script that performs the upgrade. You can either kill all processes and then do a pivot_root into the temporary rootfs, or you can use kexec --initrd=... to boot into the in-RAM root filesystem.
I am developing applications on Beaglebone board with Angstrom Linux distro.
I tend to mount root file system as read only because, it is not robust on readable/writeable configuration across power offs.
Can you make suggestions about how to mount root file system as read only?
What are the steps for mounting root file system read only and then turn it back to readable/writable?
With these step i tend to get a more robust file system.
Regards
You would need to edit the boot arguments that you pass to the kernel to use ro instead of rw for mounting the root file system. For example root=/dev/mmcblk0p1 ro. They are modifiable via the uboot environment variables
On a similar Angstrom-based system, I got the same "must specify the filesystem type" message.
After trying a few different things, I was able to remount root as ro using:
busybox mount -o remount,ro /
I have to admit I'm not certain why calling busybox directly worked when the "mount" command (which is a link to busybox) did not work, but I didn't have time to dig further.