[LEDE-DEV] /tmp/sysupgrade

[John Crispin]

On 10/04/17 15:24, Kenneth Johansson wrote:
> On 2017-04-10 14:43, John Crispin wrote:
>>
>>
>> On 10/04/17 14:25, Kenneth Johansson wrote:
>>> I found that we touch the file /tmp/sysupgrade in a few places
>>>
>>> ---
>>>
>>> git grep "tmp/sysupgrade" | grep touch
>>> package/base-files/files/sbin/sysupgrade:touch /tmp/sysupgrade
>>> package/system/fstools/files/snapshot:    touch /tmp/sysupgrade
>>> package/system/procd/files/nand.sh:            touch /tmp/sysupgrade
>>> ---
>>>
>>> But why ? did not find anything that uses that file.
>>>
>>>
>>>
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>>
>> Hi
>> procd [1] uses it to detect if an upgrade is in progress
>>     John
>>
>> [1] 
>> https://git.lede-project.org/?p=project/procd.git;a=blob;f=initd/preinit.c;h=729978ea2f2af790653baaee5ae788f05a88a177;hb=HEAD#l62
>
> Aha. there is was.  But now I got even mode questions. how do procd 
> enter preinit state again and is it just killed later since it enters 
> an infinite wait.
Hi,
procd has an open FD to the rootfs mount. if we want to flash rootfs all 
FDs must be closed prior. to achieve this procd will under certain 
circumstances do an exec to self. to prevent it from booting the system 
a second time and allowing sysupgrade to complete we use this stamp file.
     John