Re: [systemd-devel] Why systemd-journald is creating '/var/log/journal/machine_id" directory when Storage=auto
On Sun, 29 Aug 2021, Nishant Nayan wrote: > Awesome, thanks! > > Also, where can I find the code section where services And kernel logs to > journald? > After tracing from 'main' at journald.c I came across the part where > various sockets are opened and validated (/run/systemd/journal/stdout, > /dev/kmsg, /dev/log ) for journald to listen to logs of systemd services > and kernel. That is the server side part. > > Where can I find the client side journald code where services and kernel > sends their logs to journal. If programs are using sd-journal, they are using the code from src/libsystemd/sd-journal/. Programs can also implement the journal protocol themselves, using the documentation at: https://systemd.io/JOURNAL_NATIVE_PROTOCOL/ The kernel doesn't do any of this, of course. journald *reads* from the kernel ring buffer.
Re: [systemd-devel] Why systemd-journald is creating '/var/log/journal/machine_id" directory when Storage=auto
Awesome, thanks! Also, where can I find the code section where services And kernel logs to journald? After tracing from 'main' at journald.c I came across the part where various sockets are opened and validated (/run/systemd/journal/stdout, /dev/kmsg, /dev/log ) for journald to listen to logs of systemd services and kernel. That is the server side part. Where can I find the client side journald code where services and kernel sends their logs to journal. Nishant On Sun, 29 Aug 2021, 18:39 Michael Chapman, wrote: > On Sun, 29 Aug 2021, Nishant Nayan wrote: > > Also I was wondering where in the code does journald.config file changes > > are parsed? > > For example in the above code , the line :- > > if (s->storage == STORAGE_PERSISTENT) > > Here, s->storage corresponds to 'Storage' option of conf file right? > > How is it getting set when we edit the conf file? > > The configuration files are loaded in server_parse_config_file(). The > actual code that maps keys in the files to variables in the program is > generated by gperf [1] from the journald-gperf.gperf source file. > > [1] https://www.gnu.org/software/gperf/manual/html_node/index.html > > > Also, on doing "ls /run/log/journal/machine_id/" > > I can see output as following > > .journal > > .journal > > . > > . > > . > > system.journal > > > > Is 'system.journal' is the currently active journal and rest are archived > > journals? > > That's correct. >
Re: [systemd-devel] Why systemd-journald is creating '/var/log/journal/machine_id" directory when Storage=auto
On Sun, 29 Aug 2021, Nishant Nayan wrote: > Also I was wondering where in the code does journald.config file changes > are parsed? > For example in the above code , the line :- > if (s->storage == STORAGE_PERSISTENT) > Here, s->storage corresponds to 'Storage' option of conf file right? > How is it getting set when we edit the conf file? The configuration files are loaded in server_parse_config_file(). The actual code that maps keys in the files to variables in the program is generated by gperf [1] from the journald-gperf.gperf source file. [1] https://www.gnu.org/software/gperf/manual/html_node/index.html > Also, on doing "ls /run/log/journal/machine_id/" > I can see output as following > .journal > .journal > . > . > . > system.journal > > Is 'system.journal' is the currently active journal and rest are archived > journals? That's correct.
Re: [systemd-devel] Why systemd-journald is creating '/var/log/journal/machine_id" directory when Storage=auto
Also I was wondering where in the code does journald.config file changes
are parsed?
For example in the above code , the line :-
if (s->storage == STORAGE_PERSISTENT)
Here, s->storage corresponds to 'Storage' option of conf file right?
How is it getting set when we edit the conf file?
Also, on doing "ls /run/log/journal/machine_id/"
I can see output as following
.journal
.journal
.
.
.
system.journal
Is 'system.journal' is the currently active journal and rest are archived
journals?
Nishant
On Sun, 29 Aug 2021 at 17:56, Michael Chapman
wrote:
> 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.
>
Re: [systemd-devel] Why systemd-journald is creating '/var/log/journal/machine_id" directory when Storage=auto
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.
Re: [systemd-devel] Why systemd-journald is creating '/var/log/journal/machine_id" directory when Storage=auto
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");
>
> Here, system_storage.path is set to "strjoin("/var/log/journal/",
> SERVER_MACHINE_ID(s));" in previous function call.
>
> As far as I understood its saying to create '/var/log/journal' directory
> when storage is set to 'persistent'.
>
> But in either of the cases (persistent or auto) why is it creating
> '/var/log/journal/machine_id' directory ( (void)
> mkdir(s->system_storage.path, 0755); ) ??
>
> 'auto' will store logs persistently if '/var/log/journal' is created
> beforehand or else logs will be written in '/run/log/journal' .
>
> For 'auto' it should not create '/var/log/journal/machine_id' directory
> right?
All of this is guarded with:
flush_requested || flushed_flag_is_set()
In other words, this code path is used if a request to flush the journal
data from /run into /var had been received, or the runtime journal had
already been flushed in the past.
> 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 .
mkdir_p() creates parent directories, like `mkdir -p` in your shell.
[systemd-devel] Why systemd-journald is creating '/var/log/journal/machine_id" directory when Storage=auto
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");
Here, system_storage.path is set to "strjoin("/var/log/journal/",
SERVER_MACHINE_ID(s));" in previous function call.
As far as I understood its saying to create '/var/log/journal' directory
when storage is set to 'persistent'.
But in either of the cases (persistent or auto) why is it creating
'/var/log/journal/machine_id' directory ( (void)
mkdir(s->system_storage.path, 0755); ) ??
'auto' will store logs persistently if '/var/log/journal' is created
beforehand or else logs will be written in '/run/log/journal' .
For 'auto' it should not create '/var/log/journal/machine_id' directory
right?
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 .
