I'm building a custom linux image, using a non-manipulated Linux kernel 2.6.32.65.
the kernel boots just fine until it reaches this:
EXT2-fs warning: mounting unchecked fs, running e2fsck is recommended
VFS: Mounted root (ext2 filesystem) on device 3:1.
Freeing unused kernel memory: 304k freed
init: Unable to mount /dev filesystem: No such device
init: ureadahead main process (983) terminated with status 5
init: console-setup main process (1052) terminated with status 1
I tried the solutions mentioned here although the error is not exactly the same, but no luck. I tried multiple "reference" .config files. I have been googling for a bit but I can't find anything with the same problem.
I'm running this custom image on gem5 simulator, with file system from ubuntu-core and a clean kernel. earlier in the output the kernel shows this:
hda: max request size: 128KiB
hda: 16514064 sectors (8455 MB), CHS=16383/16/63
hda: hda1
So the kernel is able to see partitions just fine. I don't think this is caused by something in the file system. maybe initrd? or the kernel itself? how can I fix it?
1.) The problem is not in devfs, it seems issue is console setup. 2.) This is init issue not a linux kernel issue. 3.) Try to pass /bin/sh instead of init to kernel cmd line
I have the same problem with custom built embedded Linux.
Check you have enabled devfs in kernel .config
# core filesystems
CONFIG_PROC_FS=y
CONFIG_SYSFS=y
## devfs
CONFIG_DEVTMPFS=y
CONFIG_DEVTMPFS_MOUNT=y
Related
Im having issue with my script that calulates intergity on this version of ubunutu :
cyber#ubuntu:/$ hostnamectl
Static hostname: ubuntu
Icon name: computer-vm
Chassis: vm
Machine ID: 48d13c046d74421781e6c6f771f6ac31
Boot ID: 847b838897ac47eb932f6427361232d1
Virtualization: vmware
Operating System: Ubuntu 20.04.4 LTS
Kernel: Linux 5.13.0-51-generic
Architecture: x86-64
Im wondering if /sys/kernel/tracing/per_cpu/cpu45 is not by any chance an alive file ?
because calculating the hash of the files inside takes ifinite time.
If you want to check filesystem integrity, skip the whole /sys folder - it is an interface to the kernel.
Also it would be better if you also skip /proc (also kernel interface) and /dev (special or device files) folders. F.e - you can read from /dev/zero or /dev/urandom forever. Network mounts can give you a lot of bright moments too.
Also your script can freeze on reading pipes - it there is enough permissions it can read from a pipe forever.
If I was building such a script, I'll start from the mounts, checked their filesystems and scanned only needed ones. For example if a mount is tmpfs - it's contents is located in RAM and will be wiped after reboot.
And you totally should check it out -
https://en.wikipedia.org/wiki/Filesystem_Hierarchy_Standard
So I had to upgrade my system from 11.1 to 12.0 and now the system does not load. Stop on error Trying mount root zfs - Error 2 unknown filesystem.
And I do not have an old kernel which was good and worked well.
So How to fix mount problem?
Had tried to boot with the old kernel, but after one of the tries to freebsd-update upgrade there left only new kernel.
Expected no problems after the upgrade.
Actual - cannot load the system with Error 2 - unknown filesystem
P.S.
Found that /boot/kernel folder does not contain opensolaris.ko module.
How to copy this module to /boot partition on the system from LiveCD (this file exist on LiveCD)
Considering you have a FreeBSD USB stick ready... you can import the pool into a live environment and then mount individual datasets manually.
Considering "zroot" is your pool name
# mount -urw /
# zpool import -fR /mnt zroot
# zfs mount zroot/ROOT/default
# zfs mount -a // in case you want datasets to mount
# cd /mnt
Now do whatever you want...
You can also rollback to the last working snapshot (if there is any)
In case, your system is encrypted, you need to decrypt it first.
is there a simplest possible way to enable linux kernel driver dev_dbg debug messages (actually it's a trace style messages) hopefully without messing up with the kernel patching/recompiling or the driver implementing something extra like debugfs? perhaps there is a way to enable something SIMPLE in the kernel (like one flag?) triggering particular driver or all drivers dev_dbg (it can be filtered with the `dmesg|grep "driverName") output?
the kernel version is 4.14.
there is NO syslog/daemonlog/system log running at all. there is NO network interface and only single serial port is available. the target system is very slow and is very compact so there is NO WAY to add syslog/etc, there is nothing but dmesg where exactly would be good to see the output of the lines like:
dev_dbg(&client->dev, "bla bla bla\n");
some posts already suggested to add debug keyword for the bootargs kernel parameters unfortunately wasn't enough.
the outputs like dev_info are getting into the dmesg with no issue so it's definitely something close. thanks
the simplest way to receive dev_dbg messages without installing/configuring syslog/etc, appeared necessary to do following steps:
provide debug key into bootargs kernel parameters
append #define DEBUG at the first line of the driver file - if the driver is a single file and is using a common Makefile, or append -DDEBUG inside the CC build options if the driver contains of multiple source files and as usually has it's own Makefile
upon the kernel booted and the prompt appear to enable debug level messages by executing either dmesg -n 8 or echo 8 > /proc/sys/kernel/printk
load the driver if the module with the command either insmod <driver name> or modprobe <driver name> or if the driver is integrated into the kernel the insertion commands may vary.
example on how to assign the kernel integrated driver for the i2c bus subsystem:
echo <driver name> <i2c bus address> > /sys/bus/i2c/devices/i2c-0/new_device
side notes:
if the DTS will have a driver record assignment, manually repeated driver assignment will cause the error - in case of i2c subsystem - error EBUSY (-16), the driver will be assigned way before the command prompt and the dmesg messages will be limited to the default level (usually dev_info only)
in case if the driver has been already assigned by DTS and there is no way to exclude it temporary from the tree source - it's useful to detach and reattach it once again after the debug (trace) level messages activated
for the i2c subsystem it would require to execute a command:
echo <driver name> > /sys/bus/i2c/drivers/<drivername>/unbind
then
echo <driver name> > /sys/bus/i2c/drivers/<drivername>/bind
warning:
the kernel drivers trace mechanism will not help on debugging internal driver improper configured or missing service structures. i.e. if the driver is loaded but remain silent with no trace messages means the probe has never been executed because of some kernel expected service structures information were missing or faulty
You need to follow below three steps.
1. Make sure that your kernel is complied with CONFIG_DYNAMIC_DEBUG=y
cat /proc/config.gz | gunzip | grep CONFIG_DYNAMIC_DEBUG
If not then recompile your kernel with CONFIG_DYNAMIC_DEBUG=y
2) After boot up check that debugfs is mounted somewhere or not.
mount | grep debugfs
mostly it get mounted in /sys/kernel/debug if not then you can manually mount it anywhere like below
mount -t debugfs none /sys/kernel/debug
3) Now enable the file name for which you need dev_dbg() logs.
echo 'file <driverfilename.c> +p'>/sys/kernel/debug/dynamic_debug/control
some more commands to play with dynamic_debug/control are at https://www.kernel.org/doc/html/v4.11/admin-guide/dynamic-debug-howto.html
now you should get your debug.
If you still do not see your message then enable prink level
echo "8 4 1 7" > /proc/sys/kernel/printk
If the CONFIG_DYNAMIC_DEBUG option is not set, then dev_dbg/pr_debug can be turned into normal printk() statements with KERN_DEBUG level.
But for that you need to add #define DEBUG at beginning of file.
or add -DDEBUG while compiling
or Enable CONFIG_[SUBSYSTEM]_DEBUG=y
I used below command to turn on the Kernel log for Android. I think for Linux to it should work:
echo 'file <driverfilename.c> +p'>/sys/kernel/debug/dynamic_debug/control
You can see the driver logs in "dmesg"
Thanks
MJ
Adding "debug" to the kernel parameters will lift the kernel events log level to the KERN_DEBUG (level 7) that will pollute the kmsg buffer with debug messages for the entire kernel code and it's not usually what we want while debugging our kernel module. The same is right when we change the current kernel log level via /proc/sys/kernel/printk.
To gain fine-grained control of all log levels above the KERN_ERR for your kernel module only without messing with global kernel log level configuration just add the following lines at the beginning of your module code:
#undef dev_dbg
#undef dev_info
#undef dev_warn
#undef dev_notice
#define dev_dbg dev_err
#define dev_info dev_err
#define dev_warn dev_err
#define dev_notice dev_err
You can mount the debug filesystem manually by executing the following command:
mount -t debugfs none /sys/kernel/debug
Once done, do:
ls /sys/kernel/debug
All debug information and message would be stored there without having to re-compile.
Also, you can add the this under your /etc/fstab to make the mount go automatic when you reboot.
... If you are re-compiling your kernel anyway, then you could enable " [*] Debug File System" under "Kernel Hacking"
Good luck, I hope all goes well.
It's likely that the driver you're interested in has exported the Kconfig option to enable the debug messages. In such case, you can enable debug output from just one driver by setting the DEBUG_YOUR_DRIVER=y or YOUR_DRIVER_DEBUG=y in menuconfig and rebuilding the kernel. Search for the driver name and you will see if this is available.
For example, for NXP/Freescale i.MX pinctrl driver, I just changed DEBUG_PINCTRL to y and looked into dmesg to get the debug logs from that driver.
This was the fastest approach for me.
I try to boot from ethernet my own Linux FS :
create an initramfs with a simple and very minimal fedora structure : ok
boot with DHCP with a 2.6 kernel : ok
kernel load the initramfs : ok
a custom init.sh script is call : ok
So after the boot I have a Linux OS with an initramfs as filesystem.
With the initramfs, I have compiled some minimal applications.
The aim of this minimal boot is to make things without to have to mount
a hard disk or another filesystem.
My problem is that some applications, like mail, complain that disk
space is insuficient, and of course, df / result :
df /
Filesystem 1K-blocks Used Available Use% Mounted on
- 0 0 0 - /
So, how to make the initramfs have a mountpoint with a real capacity
(capacity = RAM capacity ?)
Thanks for any help
Yves
I have some question related to linux boot process. Initramfs is the first stage rootfile system loaded.
Init process inside iniramfs is responsible to mount actual rootfile system from harddisk to / directory.
Now my question is where is / directory created by init (init process of initramfs) to mount actual root partition. Is it in ram or hardisk ?
Also once actual root partiton is mounted then what happens to initramfs ?
If initramfs is deleted from ram then what happens to / folder created by initramfs ?
Please suggest , can some explain how does this magic works.
//Allan
What /sbin/init (of initramfs) does is, loads the filesystems and necessary modules. Then it tries to load the targeted real "rootfs". Then it switches from initramfs to real rootfs and "/" is on the harddisk. "/" is created when you installed the systems, done harddrive formating. Note, it's about reading the filesystem's content thus it's a prerequisite to load the required module first. If you've a ext3 partition of "/", then ext3.ko will be loaded and so.
Answer to second question - after doing the required fs module loading, it switches from initramfs's init to real rootfs's init and the usual booting process starts of and initramfs is removed from memory. This switching is done through pivot_root().
Answer to third - initramfs doesn't create any directory, it just load existing initramfs.img image into ram.
So, in short, loading iniramfs or rootfs isn't about creating any directory, it's about loading existing filesystem images. Just after boot - it uses initramfs to load must needed filesystems module, as if it can read the real filesystem. Hope it'll help!
With initrd there are two options:
Using pivot_root to rotate the final filesystem into position, or
Emptying the root and mounting the final filesystem over it.
More info can be found here.