[Question] Fastboot oem unlock failed to unlock bootloader - Android Q&A, Help & Troubleshooting

Hi there,
The device is
- usb debugging;
- oem unlock in Developer options;
both enabled.
adb devices recognized device.
In fastboot mode,
Code:
fastboot oem unlock
returned
Code:
OKAY [ 0.007s]
Finished. Total time: 0.019s
And the device rebooted from fastboot mode into Twrp recovery.
After the device rebooted into fastboot mode, fastboot oem device-info showed
Code:
(bootloader) Device tampered: false
(bootloader) Device unlocked: false
(bootloader) Device is_verified: false
(bootloader) Charger screen enabled: false
(bootloader) Display panel:
(bootloader) console_locked: 1
(bootloader) exec_console_unconsole: 0
OKAY [ 0.072s]
Finished. Total time: 0.072s
Bootloader remained unlocked.
In addition, fastboot flashing unlock produced
Code:
FAILED (remote: 'unknown command')
fastboot: error: Command failed
How to unlock the bootloader of this device?
May you need any further information, please do not hesitate to contact me.
Thanks in advance.

---

Hi there,
after fastboot oem unlock, the device booted into recovery.
And fastboot erase cache , it returns
******** Did you mean to fastboot format this ext4 partition?
Erasing 'cache' FAILED (remote: 'device is locked. Cannot erase')
The same result was produced after fastboot erase recovery.
How to solve it?
Thanks.
Wen
PS: The device was detected following fastboot devices

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sounds like you did not unlock bootloader right way. most devices need another predecessor step: oem unlocking in developer options.
Btw do not use fastboot erase command at all, do not follow any tutorial that suggest this.

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aIecxs said:
sounds like you did not unlock bootloader right way. most devices need another predecessor step: oem unlocking in developer options.
Btw do not use fastboot erase command at all, do not follow any tutorial that suggest this.
Click to expand...
Click to collapse
Thanks for your reply.
Could you please specify the reason that "fastboot erase" commands should not be used?

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fastboot 'erase' is dangerous command. it will erase the entire partition, which is not what you want. for example erasing recovery (like you tried) will brick your device (what was the intention behind?)
'erase' is useless intermediate step in most cases. for example when fastboot 'flash' recovery, the recovery partition will be sequentially overwritten from given file anyway. you can just skip erase it doesn't matter in such case.
partitions containing mountable file system must formatted like this (unlocked bootloader required)
Code:
fastboot format:ext4 cache
fastboot format:f2fs userdata
without formatting, the phone cannot mount the partition and will brick (few phones are smart enough to complete the formatting step automatically, though)

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aIecxs said:
fastboot 'erase' is dangerous command. it will erase the entire partition, which is not what you want. for example erasing recovery (like you tried) will brick your device (what was the intention behind?)
'erase' is useless intermediate step in most cases. for example when fastboot 'flash' recovery, the recovery partition will be sequentially overwritten from given file anyway. you can just skip erase it doesn't matter in such case.
partitions containing mountable file system must formatted like this (unlocked bootloader required)
Code:
fastboot format:ext4 cache
fastboot format:f2fs userdata
without formatting, the phone cannot mount the partition and will brick (few phones are smart enough to complete the formatting step automatically, though)
Click to expand...
Click to collapse
Hi, thank you for your replies, sorry for my belated responsiveness, owing to the recent recovery from (severe) covid symptoms.
I once used "fastboot erase recovery" because the device was stuck on the logo of newly installed recovery, and had no other means to resolve it.
So do you mean that the right way to format cache, userdata or system partitions should include the format of the partition (ex. ext4, f2fs) in adb commands fastboot format:ext4 cache, fastboot format:f2fs userdata?
If so, will the simple command fastboot erase userdata do the same thing, given that userdata is located in one simple partition, ex. mmcblk0p43?
Both fastboot format:ext4 system and fastboot erase system will wipe out the same partition (say, mmcblk0p19 where the system partition is lcoated)?
What is the function to include disk format (ext4 or f2fs) in adb commands?

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aIecxs said:
sounds like you did not unlock bootloader right way. most devices need another predecessor step: oem unlocking in developer options.
Btw do not use fastboot erase command at all, do not follow any tutorial that suggest this.
Click to expand...
Click to collapse
Hi,
I tried to unlock the device by fasboot oem unlock, it booted into recovery one more time.
And I verified in "Developer options", "OEM unlocking" is enabled.
{
"lightbox_close": "Close",
"lightbox_next": "Next",
"lightbox_previous": "Previous",
"lightbox_error": "The requested content cannot be loaded. Please try again later.",
"lightbox_start_slideshow": "Start slideshow",
"lightbox_stop_slideshow": "Stop slideshow",
"lightbox_full_screen": "Full screen",
"lightbox_thumbnails": "Thumbnails",
"lightbox_download": "Download",
"lightbox_share": "Share",
"lightbox_zoom": "Zoom",
"lightbox_new_window": "New window",
"lightbox_toggle_sidebar": "Toggle sidebar"
}
How to resolve it?
Thanks.

---

unexpected behaviour. did you try fastboot flashing unlock as well?
wenyendev said:
Both fastboot format:ext4 system and fastboot erase system will wipe out the same partition (say, mmcblk0p19 where the system partition is located)?
What is the function to include disk format (ext4 or f2fs) in adb commands?
Click to expand...
Click to collapse
Yes, but there is a difference.
erase will delete entire partition.
format will only format file system.
including file system type is optional.

---

aIecxs said:
unexpected behaviour. did you try fastboot flashing unlock as well?
Yes, but there is a difference.
erase will delete entire partition.
format will only format file system.
including file system type is optional.
Click to expand...
Click to collapse
Yes, it was the same difference.
What is the difference between "delete entire partition" and "format file system"?
Thanks.

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wenyendev said:
What is the difference between "delete entire partition" and "format file system"?
Click to expand...
Click to collapse
I assume once in your life you have created partition table with one or more partitions on single disk, be it windows or linux. every partition must formatted to receive a valid file system (NTFS FAT32 ext4 swap etc.) otherwise the raw partition is just unused inaccessable disk space.
"format file system" is when you format existing partition to valid file system type, in order to make it mountable

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Ok thanks.
What else do "delete entire partition" and "format file system" do, apart from wiping out the data?
So the difference between two is that one would be mountable afterwards, the other not?

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right. erase will just write 00 00 00 00 00 00 00 00 zeros on whole partition (invalid/empty disk space)
format will create a valid file system, so partition becomes useable.
aIecxs said:
without formatting, the phone cannot mount the partition and will brick (few phones are smart enough to complete the formatting step automatically, though)
Click to expand...
Click to collapse
to be nitpicky: partitions aren't mounted. file systems are.

---

Thanks.
So fastboot erase userdata,
fastboot erase system,
fastboot erase cache,
fastboot erase recovery
will overwrite their respective partitions (userdata, system, cache, recovery) by 00 00 00 00?
And by format like factory-reset, the data remain intact on the file system?
What are the relations between file systems and partitions?
It's good to be nitpicky in the context.
Here, by "mountable" you mean "to be able to read and write" (the file systems)?
Thanks in advance.

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if you erase cache partition, the phone will no longer boot.
wenyendev said:
And by format like factory-reset, the data remain intact on the file system?
Click to expand...
Click to collapse
on formatting, no data remains intact, new (empty) file system is written to partition.
https://www.wikipedia.org/wiki/Disk_formatting

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aIecxs said:
if you erase cache partition, the phone will no longer boot.
on formatting, no data remains intact, new (empty) file system is written to partition.
https://www.wikipedia.org/wiki/Disk_formatting
Click to expand...
Click to collapse
It is contrary to my experience.
After running fastboot erase cache, the device safely rebooted.
Here, "intact" means not overwritten by new data.

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your bootloader is locked, therefore any harmful cmd (such as flash, erase, format) is forbidden and has no effect. (btw phone gave you warning you mixed up cmds format with erase)
Code:
fastboot erase cache
******** Did you mean to fastboot format this ext4 partition?
Erasing 'cache'
FAILED (remote: 'device is locked. Cannot erase')
I said on formatting, no data remains (nothing survives) because it is overwritten by new file system.
(Maybe on quick format some data may survive, but not provided by file system and therefore invisible/non existent, like free disk space.)

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I was talking about fastboot erase cache that worked on another bootloader-free device.

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then you are lucky your phone...
aIecxs said:
(few phones are smart enough to complete the formatting step automatically, though)
Click to expand...
Click to collapse

---

aIecxs said:
unexpected behaviour. did you try fastboot flashing unlock as well?
Yes, but there is a difference.
erase will delete entire partition.
format will only format file system.
including file system type is optional.
Click to expand...
Click to collapse
fastboot flashing unlock produced the following error.

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What brand/device model/android version you are trying to unlock?
Code:
adb shell
$ getprop ro.build.fingerprint
$ getprop sys.get_unlock_ability
$ getprop ro.oem_unlock_supported
$ getprop ro.oem_unlock_allowed