[systemd-devel] Why systemd-journald is creating '/var/log/journal/machine_id" directory when Storage=auto

[Michael Chapman]

On Sun, 29 Aug 2021, Nishant Nayan wrote:
> I was looking into the code of systemd-journald and found this (in
> system_journal_open() ) :-
> 
> if (!s->system_journal && IN_SET(s->storage, STORAGE_PERSISTENT,
> STORAGE_AUTO) && (flush_requested || flushed_flag_is_set())) {
> 
>             /* If in auto mode: first try to create the machine
>              * path, but not the prefix.
>              *
>              * If in persistent mode: create /var/log/journal and
>              * the machine path */
> 
>             if (s->storage == STORAGE_PERSISTENT)
>                     (void) mkdir_p("/var/log/journal/", 0755);
> 
>             (void) mkdir(s->system_storage.path, 0755);
> 
>             fn = strjoina(s->system_storage.path, "/system.journal");
[...]
> 
> Also after reading the comment, how is it possible to create
> '/var/log/journal/machine_id' without creating the prefix? I am assuming
> '/var/log/journal' is the prefix .

Sorry, I actually misread your question here.

In Storage=auto mode, no attempt to create the /var/log/journal directory 
is made. If it doesn't exist, then the persistent journal simply fails to 
be opened.