Questions tagged [debugging]

Finding problems in a program and trying to solve these.

Filter by
Sorted by
Tagged with
0 votes
0 answers
39 views

Apache 2.4 (52) debugging, several stuck apache2 -k start at 99%-ish CPU. strace stuck on FUTEX

PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 3023 www-data 20 0 262216 19280 8848 R 93.8 0.2 3:47.05 /usr/sbin/apach Kernel release: 5.15.0-1002-aws There ...
user avatar
0 votes
0 answers
8 views

Updating ApacheDs. Changing source code to match

I was wondering how to change the ApacheDs source code to match the updated ones. What is typically the main issue in the code that needs updating. Thank you!
user avatar
0 votes
1 answer
111 views

jcmd works in console but fails in script

I'm getting mad with what should be a simple task: a java process is running, runs out of memory and a script runs. SELinux is disabled. in setenv.sh : -XX:OnOutOfMemoryError='/opt/alfresco/scripts/...
user avatar
1 vote
0 answers
249 views

How can I see which commands ansible runs and their output?

I'm new to Ansible, and yes I know this has already been asked many times, but I already tried to apply advice I saw elsewhere. I did export ANSIBLE_STDOUT_CALLBACK=debug and then ansible-playbook -...
user avatar
  • 261
1 vote
0 answers
279 views

Can Premature end of script headers be properly debugged? (getting the real error message?)

We are getting [Wed Aug 25 15:06:05.484053 2021] [proxy_fcgi:error] [pid 24792:tid 140550620227328] [client xxxx:40224] Premature end of script headers: index.php, referer: https://www.example.com/ [...
user avatar
  • 456
0 votes
0 answers
365 views

Debugging "upstream prematurely closed FastCGI request while reading upstream"

I am running an nginx + php-fpm setup. I recently ran into problem returning binary data to the Nginx server. Nginx show this in the error log: 2021/08/04 19:22:27 [error] 996463#996463: *1 upstream ...
user avatar
0 votes
1 answer
235 views

/etc/login.defs settings not taken into account: password aging

The following is done on a Ubuntu 20.04 system. This is the scenario where I am facing an issue: I edit the password aging settings in the login.defs file Then I change the password of the user with ...
user avatar
  • 148
2 votes
1 answer
249 views

How to get line number of error that .htaccess apache2 is reporting in /var/logs/error.log

I get a internal server error after adding redirects to .htaccess - I've added 600 of them. I check /var/logs/error.log [Wed May 12 16:26:02.600394 2021] [core:alert] [pid 8071] [client 127.127.127....
user avatar
0 votes
1 answer
609 views

What does `Accept-Encoding: gzip,deflate` mean?

Can someone explain what it means when I see Accept-Encoding: gzip,deflate when listening with ncat? Does it mean the body is compressed? And if so, how can I decompress it? $ nc -lnvp 4000 Ncat: ...
user avatar
  • 9,893
0 votes
0 answers
86 views

Is it possible to install Windows Debugging Tools via Powershell?

I've installed LeanSentry on one of my web servers to try and diagnose some performance issues I've been having. I need to install Windows Debugging Tools (from the Windows SDK) to get some memory ...
user avatar
0 votes
1 answer
591 views

tracking down a bash process for a df command

I’m using the tips on this SO thread. ps -awux|grep df root 15826 0.0 0.0 0 0 ? I< May22 0:00 [cifs-dfscache] myuser 3086246 0.0 0.0 216860 3212 ? Ss 16:06 ...
user avatar
5 votes
2 answers
3k views

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'...
user avatar
  • 203
-2 votes
1 answer
43 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 ...
user avatar
1 vote
3 answers
2k 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 ...
user avatar
  • 266
5 votes
1 answer
4k 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 ...
user avatar
  • 175
0 votes
0 answers
17 views

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 ...
user avatar
  • 179
3 votes
1 answer
1k 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 ...
user avatar
1 vote
2 answers
184 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 ...
user avatar
  • 109
4 votes
3 answers
7k 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 ...
user avatar
0 votes
1 answer
2k 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 ...
user avatar
  • 757
5 votes
2 answers
8k 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 ...
user avatar
0 votes
1 answer
100 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....
user avatar
  • 245
3 votes
2 answers
4k 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 ...
user avatar
1 vote
0 answers
871 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 ...
user avatar
1 vote
1 answer
150 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 ...
user avatar
0 votes
1 answer
436 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 ...
user avatar
  • 101
1 vote
1 answer
715 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 ...
user avatar
0 votes
0 answers
294 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 ...
user avatar
0 votes
1 answer
4k 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 ...
user avatar
  • 101
1 vote
1 answer
4k 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 ...
user avatar
  • 113
1 vote
1 answer
960 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 ...
user avatar
2 votes
1 answer
1k 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....
user avatar
  • 1,598
3 votes
1 answer
2k 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 ...
user avatar
  • 2,964
1 vote
0 answers
53 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 ...
user avatar
  • 188
2 votes
2 answers
7k 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 ...
user avatar
  • 2,055
3 votes
1 answer
6k 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 ...
user avatar
1 vote
0 answers
132 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 ...
user avatar
  • 23
0 votes
0 answers
375 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 ...
user avatar
  • 384
3 votes
0 answers
740 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 ...
user avatar
1 vote
0 answers
606 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 ...
user avatar
3 votes
1 answer
5k 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, ...
user avatar
  • 786
0 votes
1 answer
192 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 ...
user avatar
  • 101
1 vote
1 answer
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 ...
user avatar
  • 576
2 votes
0 answers
809 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, ...
user avatar
  • 756
2 votes
0 answers
325 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 ...
user avatar
  • 338
1 vote
2 answers
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 ...
user avatar
  • 202
0 votes
1 answer
45 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,...
user avatar
1 vote
0 answers
247 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 ...
user avatar
1 vote
1 answer
54 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,...
user avatar
  • 266
2 votes
1 answer
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 ...
user avatar
  • 131