I am using Raspberry Pi4 with 64bit OS (raspberry pi os and not NOOBS) on a 32G microSD. It was working just fine before it rebooted by itself duing an `scp` operation from a remote computer. After that, the password (default *raspberry*) is not accepted. I have access to /boot and /root partitions from the microSD on a Linux desktop.

Here is the content of /boot/cmdline.txt:

```
console=serial0,115200 console=tty1 root=PARTUUID=96e8f372-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait quiet splash plymouth.ignore-serial-consoles 

```

I tried different approaches:

* appended `init=/bin/sh` to the file cmdline.txt and `boot_delay=1` to config.txt. **Result**: the Pi stuck at rainbow screen for ever and never moves to cmd to change the password.
* appended `init=/bin/bash` to the file cmdline.txt. **Result:** the same as above (stuck at rainbow screen).
* appended `systemd.unit=emergency.target` to the file cmdline.txt. **Result:** the same as above (stuck at rainbow screen).
* appended `systemd.unit=rescue.target` to the file cmdline.txt. **Result:** the Pi stops at cmd page with `cannot open access to console, the root account is locked. press enter to continue`. By pressing enter, it normally boots and shows the login page (password incorrect).
* Pressing/holding shift at startup. **Result:** doesn't work as it is not NOOBs. Boots and shows the login page.

**What else can I do to recover?** I am trying not to do a fresh image installation as I have various libraries installed.