Loading init Ramdisk from Legacy Image at 0x90000000
Image Name: swupdate-image-…
Created:
…
Starting Kernel…
Then it loads the kernel. But I would like to access the environment in initrd and do some operation, like creating a file etc. How do I do that? I am not that well versed with ramdisk, so do not mind the ambiguity in my understanding(if any).
you need to do file operations during the boot process? or after … your question is not quite clear. Where are you mounting this ramdisk?
do you know about /dev/shm? it is a ramdisk that gets created for you … here is an example from my system:
gomer@bbb42:~$ df
Filesystem 1K-blocks Used Available Use% Mounted on
udev 220000 0 220000 0% /dev
tmpfs 49492 5468 44024 12% /run
/dev/mmcblk1p1 3647540 2865840 576696 84% /
tmpfs 247444 0 247444 0% /dev/shm
tmpfs 5120 0 5120 0% /run/lock
tmpfs 247444 0 247444 0% /sys/fs/cgroup
tmpfs 49488 0 49488 0% /run/user/1001
gomer@bbb42:~$ cat /etc/dogtag
BeagleBoard.org Debian Image 2018-10-07
gomer@bbb42:~$ uname -a
Linux bbb42 4.14.71-ti-r80 #1 SMP PREEMPT Fri Oct 5 23:50:11 UTC 2018 armv7l GNU/Linux
gomer@bbb42:~$ ls -l /dev/shm
total 0
gomer@bbb42:~$ echo foo > /dev/shm/foo
gomer@bbb42:~$ ls -l /dev/shm
total 4
-rw-r--r-- 1 gomer gomer 4 Sep 29 13:20 foo
gomer@bbb42:~$ cat /dev/shm/foo
foo
gomer@bbb42:~$
I don’t know at what point during the boot process that /dev/shm gets created if that makes any difference… is it important to do the file operations during the boot process?
I want to do file ops, before the Linux is booted. swupdate in initrd, does some checks and boots. I would like to add some script in initrd. But the initrd file provided by swupdate is not mountable. So, I was thinking about adding the script once the u-boot loads initrd(before booting Linux).
I am not sure if this works…but would like to try. So, I was thinking about doing the file ops in initrd environment(as the system is booting).
I am not aware of /dev/shm. Will look into it. Thanks for the pointer.