Lustre 1.6 Operations Manual

22.3.7 Viewing Parameters
To view the parameters set in the configuration log:
1. Unmount the MGS.
2. Mount the MGS disk as
# mount -t ldiskfs /dev/sda /mnt/mgs
3. Use the llog-reader utility to display the contents of the various configuration
logs under the CONFIGS directory.
# /usr/sbin/llog-reader /mnt/mgs/CONFIGS/testfs-client
4. Look for items marked "param".
5. Check the other logs for parameters that affect those targets, e.g. testfs-
MDT0000 for MDT settings.
The current settings allow you to easily change a parameter. However, there is no
simple way to delete a parameter. Shut down all targets and enter the --writeconf
command to regenerate the logs. Then, add back all of your modified settings.
When you enter the --writeconf command, you can set modified settings for each
device using following commands.
mdt# tunefs.lustre --writeconf --param="failover.mode=failout" /dev/sda
ost1# tunefs.lustre --writeconf --erase-params
--param="failover.node=192.168.0.13@tcp0"
--param="osc.max_dirty_mb=29.15" /dev/sda
Use the --erase-params flag to clear old paramers from the tunefs list. Without
the --writeconf command, clearing the parameters has no effect.
If you change the parameters exclusively via tunefs (not using lctl), then
tunefs.lustre --print shows you the list of parameters. For production
systems, this is the preferred way to set parameters, as the parameters sustain
--writeconf. Parameters set via lctl conf_param do not sustain --writeconf.
You can also perform similar operations without unmounting the filesystem. Run:
debugfs -c -R 'dump CONFIGS/testfs-client /tmp/testfs-client' /dev/sda
llog_reader /tmp/testfs-client
Chapter 22 Lustre Troubleshooting Tips 22-9