iw dev wlan0 station dump
This is very useful because it is helpful if you are running something like hostapd and need to see the signal strength and negotiated connection speed.
Station ff:ff:ff:ff:ff:ff (on wlan0)
inactive time: 16309 ms
rx bytes: 25451
rx packets: 325
tx bytes: 44381
tx packets: 159
tx retries: 0
tx failed: 0
signal: -72 [-72] dBm
signal avg: -72 [-72] dBm........
I had a system running a 128MB live CD image with 2.8 gigs of available RAM and the OOM kernel killer went crazy when using dd for more than 8 minutes and kept killing everything. I've read that this is due to a low-memory issue and paging in the kernel and 32-bit systems with lots of RAM.
I even enabled swapspace on my LiveCD and the issue happened 25 minutes into dd rather than 8 minutes, so what gives?
Also no swap space was ever used!
This doesn't seem to be widely known (maybe it's in some documentation that none of us read though)but there's an easy way to check the integrity of any mdadm array:
sudo echo check > /sys/block/md0/md/sync_action
-bash: /sys/block/md0/md/sync_action: Permission denied
sudo will never work, this only works as root since echo is not actually a binary/command. It is built-into bash.
Out of memory: kill process 7559 (rsync) score 635 or a child
Killed process 7559 (rsync)
I was surprised to see this in my dmesg whenmy rsync backup suddenly stalled/stopped.
This system has 3 gigs of RAM and lots of free memory so I don't understand what is happening.
rsync invoked oom-killer: gfp_mask=0x200d2, order=0, oomkilladj=0
Pid: 7600, comm: rsync Not tainted 184.108.40.206 #83