Rights of logs file zabbix_agentd.log

[SLMitch]

I have seen a bug with the right of log for zabbix_agentd : Indeed, if the log file don't exist, he is created with root as owner, and zabbix can't write in it.

This is a patch who move the first "touch" of the lof file after fork in user zabbix is done :

diff -ru zabbix-1.1-orig/src/zabbix_agent/zabbix_agentd.c zabbix-1.1/src/zabbix_agent/zabbix_agentd.c
--- zabbix-1.1-orig/src/zabbix_agent/zabbix_agentd.c    2006-06-08 15:21:33.000000000 +0200
+++ zabbix-1.1/src/zabbix_agent/zabbix_agentd.c 2006-06-08 15:26:37.000000000 +0200
@@ -204,6 +204,12 @@

        }

+       if(CONFIG_LOG_FILE == NULL)
+               zabbix_open_log(LOG_TYPE_SYSLOG,CONFIG_LOG_LEVEL,NULL);
+       else
+               zabbix_open_log(LOG_TYPE_FILE,CONFIG_LOG_LEVEL,CONFIG_LOG_FILE);
+
+
        if( (pid = fork()) != 0 )
        {
                exit( 0 );
@@ -543,11 +549,6 @@
        init_metrics();
        init_config();

-       if(CONFIG_LOG_FILE == NULL)
-               zabbix_open_log(LOG_TYPE_SYSLOG,CONFIG_LOG_LEVEL,NULL);
-       else
-               zabbix_open_log(LOG_TYPE_FILE,CONFIG_LOG_LEVEL,CONFIG_LOG_FILE);
-
        load_user_parameters();

        switch(task)

[Alexei]

Thanks for the patch. The problem is fixed.

[vrtareg]

Hi

The same problem is present in server code.

Regards
Areg

[Alexei]

It has been fixed as well.

[vrtareg]

Hi

Thank you.

Another question. Is it possible to change PID file creation part?
If it will be created as root it can be placed in /var/run and it will be possible to stop zabbix server and agent via killproc function (for init.d scripts).
I try to change creation order in code but it seems that the first agentd or server process forks one and more child processes under zabbix user and exit.
In this case in pid file i get nonexistent process number and killproc kills not correct process.

You can find my attached scripts and small patch in this thread:

http://www.zabbix.com/forum/showthread.php?t=3283

Regards
Areg

[Alexei]

Another question. Is it possible to change PID file creation part?
If it will be created as root it can be placed in /var/run and it will be possible to stop zabbix server and agent via killproc function (for init.d scripts).

Is it standard behavior of daemon processes?

When a daemon starts as root:

1. It creates PID file as root
2. chown(zabbix)

Right?

[vrtareg]

Yes, you are right

But in pid file writes the pid of the first process started from zabbix user, not the root process pid which will exit after starting child processes.
Does i am right or no?
If i start zabbix_agentd or zabbix_server process it do the following steps:

1. check is it runnig from root?
2. check if zabbix user present?
3. fork n child processes from zabbix user
4. exit

In this case in pid file writes the main process pid number which dont exists anymore after running child processes.
After this when init.d script try to stop daemon it check pid file, read pid from It and try to send TERM sygnal to this process.
If process with this pid don.t exests it sends TERM sygnal to random process named zabbix_server or zabbix_agentd.
After this server or agent dies abnormaly because they see that one of the threads dies.

Regards
Areg

P.S. Sorry for my not good English. If i describe something not correct please tell me.

[Alexei]

Thanks for the explanation, the PID issue will be fixed as well.

[just2blue4u]

i created the directory /var/run/zabbix/ with drwxr-xr-x for zabbix. so zabbix can put its pid-file there...

[vrtareg]

i created the directory /var/run/zabbix/ with drwxr-xr-x for zabbix. so zabbix can put its pid-file there...

This is not good solution because killproc function from /etc/rc.d/init.d/functions file look only in /var/run directory for the pid files.
If You call "killproc zabbix_server" it try to find /var/run/zabbix_server.pid file, read pid from it and send TERM sygnal to it.

This is correct way to stop program.

Regards
Areg

[Alexei]

Yes, you are right

But in pid file writes the pid of the first process started from zabbix user, not the root process pid which will exit after starting child processes.
Does i am right or no?

Yes, you're right. Honestly I do not see how this can be fixed... Indeed the root process exits and other processes have zabbix ownership.

[vrtareg]

Yes, you're right. Honestly I do not see how this can be fixed... Indeed the root process exits and other processes have zabbix ownership.

I think that root process can work and wait for the external kill or term sygnal, and also checks child processes.
You can check that this process dont crate any connections and dont listen to any ports.
I think that in this case the pid file and log file problems can be solved.
Alsi you can put log files in standart /var/log directory and rotate them by logrotate.

Many programs in Linux rotates their log files by the -HUP command like this:

/var/log/messages /var/log/secure /var/log/maillog /var/log/spooler /var/log/boot.log /var/log/cron {
sharedscripts
postrotate
/bin/kill -HUP `cat /var/run/syslogd.pid 2> /dev/null` 2> /dev/null || true
endscript
}

This is a standatd logrotate script for syslog. You can find them in /etc/logrotate.d/syslog file in any Linux RedHat like distribution.

It will be betther to do this because you can send messages from the child processes to main process to write messages to log file.

For example apache web server work like this. It starts one process from the rot which will do absolutely nothing except managing log files, pid file and listening port 80. if someone try to connect to server, main process starts child process under some unprivileged user (apache) and child process starting to handle html, php and other files handling.

Regards
Areg