On linux mint 17.1 Rebica start, I get the following messages:
Press c to stop all check in process.
Then after some time I am getting:
press f to fix internal errors, i ignore, s to skip mounting, m for manual recovery.
what is causing these?
this happens when upon a startup, a process takes too long, or waits for completion...
at the time you see this message, try to hit Esc, to see the actual console log to determine which process is taking that long, or eventually failing, and try to later fix it..
also investigate the output of dmesg for errors
From the second message it seems you need to run fsck on your disk .. that should still be shown in the kernel or dmesg logs.
Related
We are controlling a Keithley DMM6500 using the pyVisa library. In our setup, we are keeping an iPython kernel running (through Spyder).
The problem we're running into is the following: whenever a function that interacts with the DMM encounters an unhandled exception (like a KeyboardInterrupt), any subsequent calls to the DMM result in the error VI_ERROR_SYSTEM_ERROR (-1073807360): Unknown system error (miscellaneous error).
In order to fix this, we have tried to call device.clear() and device.close() / device.open(), but this doesn't seem to work. Even rebooting the device does not work. The only thing that fixes the issue, it seems, is to completely restart our iPython kernel.
Is there any way to programmatically restore communication with the device, such that we can avoid having to reboot the ipython kernel?
Some of your question is unclear so my answer might not help, however, it sounds like the terminal is locking the connection and you're loosing the reference.
The two way I have done this in the past:
Open the connection when talking to the device and close the connection when finished. This is useful if your connection is unstable but takes a fraction longer to open and close the connection a lot.
2)In your program you should have a try/except to handle the connection to the insturument and when the program errors you need to close the connection so that it doesn't become locked.
example:
try:
run_program()
except:
close_connection_to_all devices() # build a function to clear connection to all devices
dump_any_unsaved_data() # maybe you want to dump some of the variable to see what the data was when it errored for debug
I am not sure if this should be posted as an issue on the MongoDB github or should be posted here, so please bare with me.
What I want:
My first goal was to restart the monogd server using the Mongo Python API (pymongo). I guess that is theoretically impossible since after a shutdown, the API loses any link to the main server and can't ask it to restart.
So, I changed plans:
I just wanted to shutdown the server from my python code, pause the code (using input('Press enter')) allowing user to manually restart the mongod server and then press enter to continue the code execution after the user has restarted the server.
The way I "shutdown" the server from pymongo and wait for manual restart inside the code is as follows:
shell = MongoClient(uri)
shell['admin'].command('shutdown')
input("Press Enter button after restart.")
Problem is:
I keep getting an "AutoReconnect" error when doing this. Even after catching the error as follows:
try:
shell['admin'].command('shutdown')
except Exception as e:
if "closed" in str(e):
print("[UPDATE] Server was successfully shutdown. Please restart it.")
input("Press Enter button after you restart it.")
else:
raise e
Even after that, multiple "AutoReconnect" errors are raised. Without affecting the functionality of the code this time, just printing to stderr.
So, my question(s) are:
Is there a better way to restart the server from Pymongo? Possibly one that does not involve humnan intervention ?
How can I turn off the autoreconnect errors thrown ? Could not find any updated method to do so.
I'm using VS Code to write and debug a C++ program binding to libfuse.
Unfortunately, if you kill a libfuse process with SIGKILL, you then have to use sudo umount -f <mountpoint> before you can start the program again. It's a minor nuisance if I have to do this every time I want to stop or restart debugging, especially as I shouldn't have to authenticate to do such a regular task (the sudo is somehow necessary despite the mount occurring as my user).
While I think this is mainly FUSE's fault (it should gracefully recover from a process being ungracefully killed and unmount automatically instead of leaving the directory saying Transport endpoint is not connected), I also think there should be a way to customise VS Code (or any IDE) to run some clean-up when you want to stop debugging.
I've found that entering -exec signal SIGTERM in the Debug Console will gracefully unmount the directory correctly, stop the process and tell VS Code it's no longer debugging (status bar changes back from orange to blue). But I can't seem to find a way to automate this. I've tried using a .gdbinit file, with some inspiration from this question:
handle SIGTERM nostop
# This doesn't work as hook-quit isn't run when quitting via MI mode, which VS Code uses...
define hook-quit
signal SIGTERM
end
But as noted in the linked question, GDB ignores quit hooks when in MI mode, and VS Code uses MI mode.
The ideal solution for me would be if I could put something in a .vscode configuration file telling it to send -exec signal SIGTERM when I click the stop or restart buttons (and then wait for whatever notification it's getting that debugging has stopped, before restarting if applicable) but I imagine there probably isn't an option for that.
Even if the buttons can't be customised, I'd be happy with the ability to have a keybinding that would just send -exec signal SIGTERM to the Debug Console without me having to open said console and enter the command, though the Command Palette doesn't show anything useful here (nothing that looks like it will send a specified Debug Console command), so I don't expect there's a bindable command for that either.
Does anyone have any suggestions? Or would these belong as feature requests over on the VS Code github? Any way to get GDB to respect its quit hook in MI mode, or to get FUSE to gracefully handle its process being killed would be appreciated too.
This question is an extension for that question.
Yet again: I'm working under CentOS 6.0 and I have a remote win7 folder, mounted with:
mount -t cifs //PC128/mnt /media/net -o "username=WORKGROUP\user,password=pwd,rw,noexec,soft,uid=user,gid=user"
When remote folder is not available (e.g. network cable is pulled out) an attempt to access the remote folder locks an application I'm working on. At first I detected that QDir::exists() caused locking for 20-90 seconds (I still can't find out why such difference), further I detected that any call to stat() function leads to application lock.
I followed an advice provided in topic above, I moved QDir::exists() call (and later - call to the stat() function) to another thread and this didn't solve the problem. The application still hangs when connection is suddenly lost. Qt trace shows that lock is somewhere in the kernel:
0 __kernel_vsyscall
1 __xstat64#GLIBC_2.1 /lib/libc.so.6
2 QFSFileEnginePrivate::doStat stat.h
I did also tried to check if remote share is still mounted before trying to access folder itself, but it didn't help. Approaches such as:
mount | grep /media/net
show that shared folder is still mounted even is there is no active connection to the network.
Checking folder status differences such as:
stat -fc%t:%T /media/net/ != stat -fc%t:%T /media/net/..
also hangs for ~20 seconds.
So I have several questions:
Is there any way to change CIFS timeouts? I did try to find out but it seems that there is no appropriate parameters and no CIFS config.
How can I check if remote folder is still mounted and not get locked?
How can I check is folder exists and also not get locked?
Your problem: "An unreachable network filesystem" is a very well known example which trigger linux hung task which isn't the same of zombies process at all(killing the parent PID won't do anything)
An hung task, is task which triggered a system call that cause problem in the kernel, so that the system call never return.
The major particularity is that the task is declared in the "D" state by the scheduler which mean the program is in an uninterruptible state. This mean that you can do nothing to stop you program: You can trigger all signal to the task, it would not respond. Launching hundreds of SIGTERM/SIGKILL does nothing!
This the case whith my old kernel: when my nfs server crash, I need to reboot the client to kill the tasks using the filesystem. I compiled it a long time ago (I have still the build tree on my hdd) and during the configuration I saw this in lib/Kconfig.debug:
config DETECT_HUNG_TASK
bool "Detect Hung Tasks"
depends on DEBUG_KERNEL
default LOCKUP_DETECTOR
help
Say Y here to enable the kernel to detect "hung tasks",
which are bugs that cause the task to be stuck in
uninterruptible "D" state indefinitiley.
When a hung task is detected, the kernel will print the
current stack trace (which you should report), but the
task will stay in uninterruptible state. If lockdep is
enabled then all held locks will also be reported. This
feature has negligible overhead.
It was only proposing to detect such tash or panic on detection: I don't checked if recent kernel actually can solve the problem (It seems to be the case with your question), but I think it didn't worth enabling it.
There is second problem : normally, the detection occur after 120 seconds, but I saw also a Konfig option for this:
config DEFAULT_HUNG_TASK_TIMEOUT
int "Default timeout for hung task detection (in seconds)"
depends on DETECT_HUNG_TASK
default 120
help
This option controls the default timeout (in seconds) used
to determine when a task has become non-responsive and should
be considered hung.
It can be adjusted at runtime via the kernel.hung_task_timeout_secs
sysctl or by writing a value to
/proc/sys/kernel/hung_task_timeout_secs.
A timeout of 0 disables the check. The default is two minutes.
Keeping the default should be fine in most cases.
This also works with kernel threads: example: make a loop device to a file on a fuse filesystem. Then crash the userspace program controlling the fuse filesystem!
You should a get a Ktread which name is in the form loopX (X correspond normally to your loopback device number) HUNGing!
weblinks:
https://unix.stackexchange.com/questions/5642/what-if-kill-9-does-not-work (look at the answer written by ultrasawblade)
http://www.linuxquestions.org/questions/linux-general-1/kill-a-hung-task-when-kill-9-doesn't-help-697305/
http://forums-web2.gentoo.org/viewtopic-t-811557-start-0.html
http://comments.gmane.org/gmane.linux.kernel/1189978
http://comments.gmane.org/gmane.linux.kernel.cifs/7674 (This is a case similar to yours)
In your case of the three question: you have the answer: This probably due to what is probably a well known bug in the vfs linux kernel layer! (There is no CIFS timeouts)
After much trial & error I found a solution that persists.
# vim /etc/fstab
//192.168.1.122/myshare /mnt/share cifs username=user,password=password,_netdev 0 0
The _netdev option is important since we are mounting a network device. Clients may hang during the boot process if the system encounters any difficulties with the network.
https://www.redhat.com/sysadmin/samba-windows-linux
I'm working with an embedded computer that has a Debian on it. I already manage to run a command just before it has booted and play the "bell" to tell that is ready to work, and for example try to connect to a service.
The problem is that I need to play the bell (or run any command/program) when the system is halted so is safe to un-plug the power. Is there any runscript that run just after halt?
If you have a look in /etc/init.d, you'll see a script called halt. I'm pretty certain that when /sbin/halt is called in a runlevel other than 0 or 6, it calls /sbin/shutdown, which runs this script (unless called with an -n flag). So maybe you could add your own hook into that script? Obviously, it would be before the final halt was called, but nothing runs after that, so maybe that's ok.
Another option would be to use the fact that all running processes get sent a SIGTERM followed (a second or so later) by a SIGKILL. So you could write a simple daemon that just sat there until given a SIGTERM, at which point it went "ping" and died.