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I'm using an embedded Linux OS which was built using yocto. I'm trying to alter busybox syslogd in order to have it output to both a file & buffer. so I can use logread -f as well as have the output saved onto a file for future in case I need to look at them later. Now the issue I'm seeing is that after I alter the syslogd-startup.conf file to the following:

DESTINATION=" file buffer"       # log destinations (buffer file remote)
LOGFILE=/mnt/userrw/sd/logs   # where to log (file)
REMOTE=loghost:514      # where to log (syslog remote)
REDUCE=no           # reduce-size logging
DROPDUPLICATES=no       # whether to drop duplicate log entries
ROTATESIZE=2000           # rotate log if grown beyond X [kByte]
ROTATEGENS=2           # keep X generations of rotated logs
BUFFERSIZE=2000         # size of circular buffer [kByte]
FOREGROUND=no           # run in foreground (don't use!)
#LOGLEVEL=7         # local log level (between 1 and 8)

and then I run restart command on /etc/init.d/syslog and then run the following command:

ps aux | grep syslogd

I get the following confirming that my args for syslogd is correct:

ps aux | grep syslogd
root      1648  0.3  1.7   4236  2588 ?        S    14:35   0:00 /sbin/syslogd -n -O /mnt/userrw/sd/logs -s 2000 -b 2 -C2000
root      1671  0.0  0.3   2240   496 pts/0    S+   14:35   0:00 grep syslogd

BUT the issue is that It never prints to the file. Only to the buffer. if I take out the-C2000 arg (i.e. have DESTINATION=file only) then it does print to a file. How can I get it to output to BOTH file & buffer? Is this not doable? my syslogd.conf file is empty. Should I be using that to output to file and use the syslogd-startup.conf to output to buffer?

  • Personally I wouldn't try to modify the source. Instead work on a solution to wrap the existing tools. such as busybox syslogd -C2000; busybox logread -f | tinylog -k 2 /path/to/logs. (tinylog and other alternatives are discussed here). – Patrick Jun 11 '18 at 19:51
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Looking at some sources for syslogd.c in a version of busybox, it looks like this is not possible. The appropriate code seems to be:

    if (LOG_PRI(pri) < G.logLevel) {
          if ((option_mask32 & OPT_circularlog) && G.shbuf) {
                log_to_shmem(G.printbuf);
                return;
          }
          log_locally(now, G.printbuf, &G.logFile);
    }

So if you log to buffer, it returns without logging to file too. It seems a bit shortsighted. Perhaps you could patch your yocto to remove the return; statement.

  • Just to clarify you also need to take out the ``` //match = 1; ``` line a couple of lines above this if statement. I tested it and it works. Now I have to figure out how to apply it as a patch to my yocto bitbake build – JJ Adams Mar 21 at 21:04

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