Apologies for my lack of dev knowledge and general amateur hackiness,
I am running CC v15.05 and trying to get logging to to an external usb drive working. I have spent many hours reading and trying to understand how this works and have managed to come up with the following commands which are set in the browser client (system > startup > local startup) to run at start up:

mount -t ext4 -U <UID> /mnt/usbdrive -o rw
sleep 1
mkdir /mnt/usbdrive/logs/syslog/$(date +"%d.%m.%Y-%H.%M")
sleep 1
logread -f > /mnt/usbdrive/logs/syslog/$(date +"%d.%m.%Y-%H.%M")/logread.txt&
sleep 1
mkdir /mnt/usbdrive/logs/klog/$(date +"%d.%m.%Y-%H.%M")
sleep 1
dmesg > /mnt/usbdrive/logs/klog/$(date +"%d.%m.%Y-%H.%M")/dmesg.txt&
exit 0

I normally power off my unit every night so what I want to do is have openwrt log both logs to a seperate folder which it makes with the days date as the folder name when I power the unit on each day. To my immense surprise this actually works! but alas it only works intermittently at best, sometimes it logs every day for a few days and sometimes it doesnt work for weeks on end. I have tried adjusting the sleeps, taking them out, putting them back in and varying the lengths. But my knowledge is lacking on any thing else i can tinker with and i find myself unable to get this working reliably,
So I would be really grateful if someone could help me with this, any ideas or any help, pointers etc would be very much appreciated.

Cheers,
L

Not sure if this is related to your problem or not... I've made this mistake many times myself...

'>' = Overwrite log file
'>>' = Append to log file

Example:

echo "this is a test" > /tmp/tmplog
echo "this is not a test" > /tmp/tmplog
cat /tmp/tmplog

should produce

Or:

echo "this is a test" >> /tmp/tmplog
echo "this is not a test" >> /tmp/tmplog
cat /tmp/tmplog

should produce

Be sure to either setup logrotate or clear the logs now and then... If you only need them temporarily, put them in /tmp and it clears when the machine reboots. This could also be the problem. Resources extremely limited on a router

Cheers back to you

(Last edited by mys5droid on 20 Feb 2017, 04:43)

I think I happened upon a solution to this, i installed "libdbi" (opkg install libdbi) and suddenly after 3 reboots in a row i am getting the new syslog/date.time, and klog/date.time folders each boot, each folder,containing the correct log as expected!
.

*Note libdbi did not solve my issue. It worked for 3 reboots after I installed libdbi but has only worked once since then. I think the problem may be something to do with openwrt not having a time immediately after startup, as it has to wait for the external modem to get a web connection before it can get time. but adding in a sleep of up to 300 seconds before the logread command still does not solve the problem.
I will continue trying to figure this out and post here if i find a solution.

I think I may have finally cracked this one, I found a config file at /etc/ulogd.conf which had a setting for the syslog that I experimented with ages ago, and that I long ago removed from the web interface. Makes me wonder if the web interface may be a little bit buggy?

When I use logread with -f the log records the subsequent entries, but misses out on the messages prior to the command running, without -f i get the prior messages. So I chain 2 commands to get all the data.
The commands that currently seem to be working when run at start up are as follows:
mkdir /mnt/usb/logs/syslog/$(date +"%d.%m.%Y-%H.%M") ; logread > /mnt/usb/logs/syslog/$(date +"%d.%m.%Y-%H.%M")/logread_st.txt ; logread -f > /mnt/usb/logs/syslog/$(date +"%d.%m.%Y-%H.%M")/logread.txt&
mkdir /mnt/lusb/logs/klog/$(date +"%d.%m.%Y-%H.%M") ; dmesg > /mnt/usb/logs/klog/$(date +"%d.%m.%Y-%H.%M")/dmesg.txt&
exit 0.