Questions tagged [debugging]

Finding problems in a program and trying to solve these.

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program runs on windows server but crashes inside container. exit status: -1073741502

I have a program that runs just fine on a Windows 2019 Datacenter Server: WindowsProductName : Windows Server 2019 Datacenter WindowsVersion ...
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any way to know when nginx stalls a request, because uwsgi server ran out of workers

I'm having an nginx setup with a uwsgi server with n workers. if I perform n+1 requests in parallel, then the last request is stalled until one of the n uwsgi workers finished handling a request. I ...
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is there any reliable way to correlate nginx and uwsgi requests / logs?

I am having a setup with nginx + uwsgi. Both servers create logs. I wondered whether there would be any way to correlate nginx and uwsgi requests (und thus their logs) In most cases the requesting IP,...
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nginx. How to log ssl errors without blowing up the server logs

I have a web site, that is visited by many different mobile devices and embedded devices. Quite often I encounter the issue, that some devices cannot connect. The reasons can be: the device doesn'...
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1answer
35 views

How to log a single-board computer events?

I have a single-board computer, I want to knows whats going on when it boot up and start up because i never get access to its BIOS, can I log the events/activities happening on the board when it get ...
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How to debug failed SuexecUserGroup under apache2 VirtualHost?

When a VirtualHost's SuexecUserGroup directive fails to switch the user executing a script as directed, it is mysterious as to how one goes about debugging. The /var/log/apache2/suexec.log is empty ...
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3answers
182 views

How to verbose log dhcp messages with options values

I am trying to configure dhcp PXE server, but client is not booting as expected. Is there a way how you can watch transferred requested and responded options between client and server? I want to be ...
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1answer
1k views

Ubuntu Server with systemd - how to get a backtrace or coredump?

I'm using Ubuntu 18.04 Server with systemd. Recently a program my department has developed crashed twice within a day with the following error: Jun 07 06:33:07 xxx systemd[1]: xxx.service: Main ...
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How to extract system startup logs from guest esp. on boot failure?

Given you have a libvirt guest VM which has all possible startup logs verbosely enabled (kernel loglevel, syslogd, dmesg etc. depending on distro). How to extract these startup logs to the host ...
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1answer
567 views

How to debug linux startup hang

My ubuntu system hangs on the startup. It hangs on [OK] items like usual on boot. Interestingly, I am able to ssh onto this machine, but the boot never finishes and login screen doesn't appear. What ...
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1answer
112 views

Set ASPNETCORE_ENVIRONMENT in Google Cloud Flex App

I have an error in my asp.net core 2.1 app and would like to set the ASPNETCORE_ENVIRONMENT setting to Development so that I can better debug. There are samples for the appsettings.json file, but the ...
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2answers
2k views

Monitoring HTTP 5xx errors in an Azure App Service

The Azure App service UI used to have an ability to inspect 5xx errors directly. Since we starting using Azure, the UI has been changing almost constantly though, and this ability seems to have ...
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693 views

Preview or debug (dry-run or trace) systemctl actions (start, stop, restart, etc.)

Without having to manually trace dependencies, e.g. with systemctl show or systemctl cat, and manually inspect the state of the system with systemctl status and systemctl list-units, is there a way to ...
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2answers
4k views

Why is MemAvailable a lot less than MemFree+Buffers+Cached?

I'm running a Linux workstation without swap and I have installed earlyoom daemon to automatically kill some processes if I'm running out of RAM. The earlyoom works by monitoring kernel MemAvailable ...
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1answer
58 views

How to interpret the debug output from Amavis->Spamassassin?

Could please someone explain how Spamassassin build the following strings: Oct 17 14:00:30 server amavis[29497]: (29497-02) SA dbg: uridnsbl: domain amazonaws.com in skip list, host sns.eu-central-1....
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2answers
738 views

How do I Identify an anonymous process that's changing a system setting?

I see an anonymous process changing the time of my systemtime to UTC every 80 sec. Using the journalctl -f command I only see a message that says 'systemd[1]: time has been changed' but it doesn't ...
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787 views

PHP FPM pool www - 100% spikes when executing scripts - how to debug

I am experiencing weird 100% spikes of cpu when loading drupal pages. It started several months ago and now Im trying to debug this. I moved same database and files to new hosting - everything runs ...
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1answer
102 views

Why does my VM become slower during CPU-heavy tasks after some days of runtime?

I'm dealing with some strange problem for some time now: After some days of runtime, one of my VMs seems to become slower on CPU-heavy tasks. One example were this happens is reading virus signature ...
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1answer
206 views

Network timeouts: how to debug?

I'm experiencing network timeouts when trying to fetch libraries from https://rubygems.org and I'd like to figure out why. It only seems to affect requests made from my home network. If I take my ...
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1answer
399 views

What are all/most ways to enable/disable usage of async file-io in Linux?

To make a long story short, I have two identical servers hosting VMs using VirtualBox and both servers host one VM each nearly setup the same way, only that one is production and the other for ...
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192 views

How to enable/install kernel-debuginfo linux-4.14.14 on amzn-linux? [duplicate]

I'm on an amzn-linux instance which by default runs linux-4.9. I've compiled and booted linux-4.14.14 from source and I've compiled systemtap from source. Now I'd like to get them both working nicely ...
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1answer
2k views

NTP rejecting upstream due to “peer_dist”

Currently NTP is rejecting its upstream and is drifting quite badly (15 seconds of offset so far and growing). When checking the reason using ntpq the flash code is flash=400 peer_dist. Checking the ...
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1answer
2k views

How to check why a write failed? [closed]

If I was to debug a service on a machine and I determined that a write was failing, how could I check why the write failed? I know the system call in C will return -1 and then we can check what ...
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1answer
474 views

Can not connect right now. can not assign requested address?

We are experiencing high load on our dedicated servers lately. Users see the error message "can not connect right now. can not assign requested address" popping up randomly. We have 2 Linux ...
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1answer
574 views

What might be causing repeated mmap/munmap in strace results?

I have a (node.js) application which is occasionally causing 100% CPU usage. I've attached to the process with strace when it's been in this state - but I don't know what to make if the strace output....
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1answer
1k views

Debug DNS: What to do if host name resolution does not work as expected?

The current search results for "debug dns" don't reveal a guide-line what to do, if you (as user/client) think there is something wrong with the host name resolution. What steps can I do to narrow ...
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51 views

ASP.NET MVC App Redirects Break in Azure

Info I'm developing a web application in ASP.NET MVC. It works great running locally (or even on a test server on my network). The moment I push it up to Azure, a couple of the redirects break ...
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2answers
4k views

how to debug/troubleshoot collectd?

I have an issue with custom script using exec plugin. From shell the script works well and nothing useful in /var/log/collectd.log. LoadPlugin logfile <Plugin logfile> LogLevel info ...
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1answer
4k views

How to debug/log 502 Bad Gateway from reverse proxy?

We're running a web service and hitting 502 Bad Gateway randomly. The 502 is reported by reverse proxy (Apache 2.4.x) while talking to backend server (Apache 2.4.x). The problem randomly re-appears ...
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124 views

SSD bandwidth issue and analysis

I have Intel's P3700 SSD mounted on a Lenovo x3650 M5 server with two Intel Xeon E5-2630 v3 CPUs. The server is running Ubuntu 14.04 with 4.6.4 Kernel. I've been using fio to benchmark the SSD using ...
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323 views

Drupal on Apache: Consecutive PHP errors “Maximum execution time of 240 seconds exeeded”

This Apache/MySQL server (Debian 8) running a Drupal site shows a strange behaviour: There's always one Apache process running with 100% CPU utilization (according to htop). Every four minutes (~240 ...
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432 views

Obtaining a Crash Dump from a dying IIS ASP.NET Worker Process

(Not sure if this is an IIS problem or not, so if this is better suited for SO I'll happily move it...) We have an IIS-hosted application that is sporadically dying, and the event logs claim that the ...
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470 views

debugging “eth interface using wrong IP” on server

My Uni provided me two hostnames and static IPs for two interfaces on my Fedora Server 23. My idea is to use one hostname for production and another for dev branches. It should work as: bio-db.uni.edu ...
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1answer
3k views

Verifying RADIUS server is sending the correct certificates?

How can I see the TLS (SSL) certificates that my RADIUS server is using, to make sure it is sending the correct certificate and chain? I am implementing 802.1x authentication with a RADIUS server, ...
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1answer
170 views

Log all bash actions with multiple scripts

Using the command below, I can log all actions that happened inside that script. bash -x script.sh Sadly, the script calls another script, which does not have the -x setting active then, i.e. the ...
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1answer
3k views

Occasional “failed to respond” from AWS hosted Elasticsearch

We have an Elasticsearch cluster hosted on Amazon Elasticsearch Service (AWS). We are using the Jest Java HTTP Rest client for ElasticSearch. Every now and then (perhaps 1 in 10,000 requests), it ...
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688 views

How to reliably capture Linux kernel log messages in case of a system debilitating crash (BUG, panic)?

I'd like to have access to the lines/tracebacks/whatever whispered by the kernel right before dying. This has proven problematic, because all interfaces I have access to become disabled. Post-reboot, ...
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249 views

Show or log long queries with values instead placeholders

I have any very long sql query in postgresql. I tried show what postgress do with: select * from pg_stat_activity unfortunately I see something like: select some_fields from anytable1 anytable2 ...
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2answers
2k views

bizarre 404 on nginx

i have a location block for / that passes any virtual paths to index.php as instructed on the nginx pitfalls page. i have been using this setup for some time now, but recently i have noticed that some ...
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1answer
43 views

Debug Logging daily task

I manage a domain with 4 domain controllers and i have been asked to enable Debug Logging for Incoming and Request packets. I have set the maximum size of the log file to 500MB. First question I have,...
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0answers
173 views

ProcessMonitor boot logging claims disk is full

I'm trying to debug an issue where Windows 7 logoff will hang about once in every 5-10 logoffs forcing a hard reboot. I've installed Process Monitor (v3.2) and am running boot logging to try and find ...
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1answer
52 views

Server frequently hangs, my client wants me to do X while the proper solution is Y

This question is more on etiquette rather than an actual server issue. 2 servers owned by a client of mine frequently stop responding (Fast, then really sluggish as in it takes 1 minute to execute ls,...
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1answer
3k views

What are the first steps to debug nginx default page not showing on fresh Ubuntu vm install?

On a fresh Ubuntu 14.04 virtual machine I've run the following commands: sudo apt-get update sudo apt-get upgrade sudo apt-get install nginx sudo service nginx start In a browser, if I go to the ...
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279 views

CoreOS Random Reboot Kernel Panic with Obscure Message - How to debug?

I'm relatively new to the CoreOS world, we had a server reboot and the messaging in the Journal is extremely vague: Sep 18 07:10:27 ip-x-x-x-x.us-west-2.compute.internal kernel: BUG: unable to handle ...
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1answer
1k views

What steps are required to debug a memory.dmp? (walkthrough included)

I woke up to this in my eventlog today: The computer has rebooted from a bugcheck. The bugcheck was: 0x000000ef (0xffffe0018668f080, 0x0000000000000000, 0x0000000000000000, 0x0000000000000000). A ...
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1answer
551 views

Tons of 500 errors like - fcgid:warn Bad file descriptor: client mod_fcgid: ap_pass_brigade failed in handle_request_ipc function

I copied a site over to GoDaddy from LiquidWeb because LW experts were unhelpful even if more knowledgeable. GD is hit or miss. On the Godaddy hosting I get 500 errors constantly when in admin ...
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1answer
1k views

Tracking down a memory leak

I previously asked a question about a server that had a very high nonpaged pool memory utilization and someone explained how to use poolmon to track down the problem driver. I did this, but I'm not ...
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1answer
61 views

Error with a specific bash script

I must first of all shamefully admit that I unfortunately know nothing about scripts... I am simply trying to use one that seems to fit my goal. I am running a VPS node with OpenVZ, and I need a ...
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1answer
471 views

Debugging random SQL login failure from Web Server

This is a very basic level question, but it could really benefit from some extra help in the diagnosis. We have a 2005 SQL Server Named: SERVERNAME-PROD We have a Web Apps Server that's running IIS 8....
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1answer
155 views

Installation of FreeBSD freezes on VMware

I am trying to install FreeBSD on VMware by mounting FreeBSD-9.2-RELEASE-i386-dvd1.iso. The installation proceeds fine untill i reach the following screen I have been waiting for an hour and ...