Intermittent TFTP Failure

[ianabc]

Hi Lindsay,

The “Cannot allocate memory” messages look a bit worrying to me. Does the machine have enough RAM? Could you try running “free -m” in a command window? e.g. here is my fog server
[CODE]
total used free shared buffers cached
Mem: 996 565 431 0 11 382
-/+ buffers/cache: 172 824

Swap: 2043 0 2043
[/CODE]
My fog server is a virtual machine with 1GB of ram, from the numbers above I have 431Mb free and around 400Mb in cache.

[LindsayS]

[ATTACH=full]1171[/ATTACH]
This is from first thing this morning.
tftp failed again last night, but, as usual, restarted without issue.
I’ll try checking on the memory consumption again later today, since it looks like it is fine right now.
FOG is currently running on what used to be a Windows server that was taken offline when we got new ones.

[url=“/_imported_xf_attachments/1/1171_FOGMemory.jpg?:”]FOGMemory.jpg[/url]

[ianabc]

I think you should be OK for memory, 4GB seems like plenty. As I said, my setup is only using 1GB and I’m not seeing the problems, before you dig too deep looking for answers, you should check that the problem isn’t firewalling.

If 0.32 was working and there have been no network changes since then there probably isn’t a network firewall, but you should double/triple check that the fog server doesn’t have one. On Ubuntu 11.10 you should check
[CODE]
$ sudo iptables -nL
Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain FORWARD (policy ACCEPT)
target    prot opt source              destination       

Chain OUTPUT (policy ACCEPT)

target    prot opt source              destination   

$ sestatus
[/CODE]
You should also check SELINUX, make sure it is either disabled or in permissive mode
[CODE]
$ sestatus
SELinux status: enabled
SELinuxfs mount: /selinux
Current mode: permissive
Mode from config file: permissive
Policy version: 24

Policy from config file:        targeted

[/CODE]
And you might want to just double check that you are NOT using tcp_wrappers: just check that /etc/hosts.allow and /etc/hosts.deny are empty or only have comments in them. Once you have confirmed those things we can start tracking down the problem without going in circles

[LindsayS]

Results of iptables -nL looked exactly like yours.
Running sestatus gives me "The program ‘sestatus’ is currently not installed’. I assume that this means SELinux is not installed also?
hosts.allow and hosts.deny both had only comments in them.

Thanks for your help. I appreciate the inclusion of the commands I need to find the info out. Saves me a lot of digging.:)

[ianabc]

OK, the network sounds clear and those error messages you were getting from tftp.hpa are very suspicious.

I don’t have an ubuntu system to test with, but on CentOS systems tftpd is started by inetd, if ubuntu is the same then when a client makes an incoming connection to the fog server for tftp, inetd spawns an instance of in.tftpd to handle the connection. It looks like, in your case, when that happens your system can’t allocate memory for tftpd so it never gets spawned, that is why your tftp sessions fail. The difficult part is figuring out why there is no memory for tftpd.

As I mentioned above, I don’t think it is a physical problem, 4GB seems like plenty of RAM - I get by with much less. It is possible that some runnaway process is eating up all of your ram, but if your system was genuinely memory starved I would expect more problems than just a failing tftpd server.

Could you attach a copy of your /var/log/messages or /var/log/syslog file? We might be able to spot the root cause in there.

Also could you periodically have a look for any tftp processes
[CODE]
$ ps -ef | grep tftp
root 5007 1138 0 12:38 ? 00:00:00 in.tftpd -s /tftpboot
root 5010 4980 0 12:38 pts/0 00:00:00 grep tftp
[/CODE]
It would be interesting to see if it is running and if more than one process is spawned.

Finally after your machine has been running for a while you can get a list of the most memory hungry processes by running ps, e.g.
[CODE]
$ ps -eo pid,rss,vsz,comm= | sort -n -k 3 | tail -n 20
5461 688 100944 tail
5459 996 108124 ps
1192 1540 108168 mysqld_safe
4980 1924 108308 bash
1406 1360 117300 crond
5460 868 155432 sort
955 1560 249084 rsyslogd
1413 11140 250640 FOGTaskSchedule
1427 10944 250640 FOGImageReplica
1420 11212 250896 FOGMulticastMan
1398 9544 271660 httpd
1462 10548 370800 httpd
1460 10576 370808 httpd
1458 10480 371024 httpd
1461 10764 371024 httpd
1457 10724 371040 httpd
1463 18528 378748 httpd
1459 18280 378752 httpd
1456 19196 379668 httpd
1294 27708 640800 mysqld
[/CODE]
If you could do this around the time that tftp dies we might have a chance of catching the reason why.

[LindsayS]

Good morning,
I haven’t forgotten about your reply. I was just waiting for tftp to fail so that the logs and responses I give you are actually useful. Its been two days, and I haven’t had to restart once.
The only thing I’ve done differently is not uploaded a new image. I have one that is almost ready for upload, so I’ll do that and see if I can get it to fail again. If that works, I should have the requested info soon.
Thanks again for your help.

[ianabc]

No problem. I hope it works for you

[LindsayS]

Alright, here is the latest:
It appears that the failures are somehow related to Image uploads to Fog. After 2 days without failure, I started an image upload, went to a meeting, and two hours later, when I got back, tftp was broken. The failure doesn’t seem to happen immediately, since I’ve seen clients continue to connect to Fog immediately after an image upload.

The info you requested is here:

[CODE]$ ps -ef | grep tftp
fog 11648 8967 0 12:03 pts/0 00:00:00 grep --color=auto tftp
[/CODE]

[CODE]$ ps -eo pid,rss,vsz,comm= | sort -n -k 3 |tail -n 20
1577 4584 60608 indicator-sessi
1592 5340 63672 indicator-messa
1581 6104 69116 indicator-datet
1641 4860 69804 indicator-sessi
32691 14640 74444 gnome-terminal
1560 6132 77264 indicator-datet
32186 18416 77768 unity-panel-ser
1405 18236 77936 unity-greeter
27376 22500 85372 unity-2d-panel
1615 3456 87192 pulseaudio
28537 11252 87348 nm-applet
27090 3940 87444 pulseaudio
1584 4736 115080 indicator-sound
28576 36108 123692 nautilus
25822 13444 124244 gnome-settings-
12697 122096 126196 find
1528 5724 132244 indicator-sound
832 28392 159192 mysqld
3170 73260 219168 soffice.bin
27380 39584 244452 unity-2d-launch
fog@CLS-FOG:~$
[/CODE]

I checked the memory usage during the failure
[code] $ free -m
total used free shared buffers cached
Mem: 4031 3757 273 0 60 3193
-/+ buffers/cache: 503 3527
Swap: 4092 0 4092
[/code]
and after running sudo restart tftpd-hpa
[CODE]free -m
total used free shared buffers cached
Mem: 4031 1349 2681 0 78 289
-/+ buffers/cache: 981 3049
Swap: 4092 0 4092
[/CODE]

Attached is the syslog from today

[url=“/_imported_xf_attachments/1/1175_syslog.txt?:”]syslog.txt[/url]

[ianabc]

I’m not sure at the moment. I’ll take a look at your syslog later, it certainly still looks like a memory leak in some process to me (my guess would be gnome somewhere - if you don’t need a desktop on your fog server just uninstall it).

If you don’t want to uninstall gnome just yet make sure you apt-get update && apt-get upgrade the system. It’s possible whatever program is leaking has been fixed already.

If you want to try the system without a desktop for a while you could try
[CODE]
$ sudo service lightdm stop
[/CODE]
You should end up at a black console with white text. Run your upload/download tests and see if the problem is fixed.

[ianabc]

One thing I just noticed, the timestamp on your tftpd entries in syslog are all really weird, I’m not sure why, and I don’t see how it could cause a problem, but it is odd.