Questions tagged [strace]

strace is a debugging utility for tracing system calls and signals under Linux.

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Typing in the Terminal on Ubuntu takes seconds until the typed character appears

The problem: typing in the terminal on Ubuntu takes seconds until the typed character appears. I first noticed this after I moved large chunks of data onto another LUKS encrypted HDD which I mounted ...
VerteXVaaR's user avatar
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When (and how) are file permission/access decisions made in kernel space?

(I think) I have a relatively good understanding of how Linux permissions work - traditional Unix DAC permissions, and how they're represented, security context in relation to processes (i.e. cred ...
genericuser99's user avatar
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How to perform strace on shell without changing your current shell?

I use strace to trace the behavior of a bash process. The purpose is to find out the order bash loads its configuration files. I am running the following command under zsh: strace -e openat bash ...
Visrut's user avatar
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How to parse strace recvfrom syscall?

I strace a curl command: strace -s 2000 -f curl google.com and see 2 DNS queries recvfrom(3, "\302\325\201\200\0\1\0\1\0\0\0\0\6google\3com\0\0\34\0\1\6google\3com\0\0\34\0\1\0\0\0\362\0\20*\0\...
Rocherlee's user avatar
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log out from slim, or slim restart results in blank screen for several minutes

I am using slim login manager. when I log out from my session, or restart slim from the commandline: service slim restart I get blank console for couple of minutes, before the slim login screen ...
Martin Vegter's user avatar
2 votes
1 answer
824 views

Debugging strange EACCES (Permission denied) permission error

I have a symlink to a world-readable file that a c program is being unable to read. redshift is supposed to pick up configuration from $HOME/.config/redshift/redsihft.conf automatically, but it wasn't....
user84207's user avatar
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How to trace file descriptor duplication?

I am learning to use redirection. the typical operation is like below: command > file 2>&1 Refer to APUE 3.10 and 3.12, I think the critical syscall sequence is like below: open(...
Yao Li's user avatar
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condensing locale requests on every program load

I ran strace on a number of programs (used syntax strace -fe trace=open --insert program here-- ) and every time I execute a program that automatically forks other processes, I notice lines similar to ...
mike_s's user avatar
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How to trace on continuously running process?

So I wanted to know how files are opened by zsh like .xinitrc, .xprofile, .zprofile, and exactly in which order. So I have decided to strace on zsh process with the grep command to see how the open ...
Visrut's user avatar
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How can I get a custom tmux.conf file to work with tmux 3.3a? `-f` flag not working as expected

I have tmux and wanted to set some custom configurations, but I cannot find a default tmux.conf file. tmux -V tmux 3.3a According to the manpage: -f file Specify an alternative ...
Stonecraft's user avatar
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Process stucked at recvfrom syscall

A process is stucked at recvfrom syscall. > sudo strace -p 4146278 strace: Process 4146278 attached recvfrom(9 ... I looked up under /proc/4146278/fd. fd 9 seems to be a socket. > sudo ls -al /...
Wei Qiu's user avatar
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vim very slow over SSH connection

I have a non-stellar SSH connection to some machine; the echo time is... I don't know, 0.2 seconds or so. Anyway, when I start vim, say with no input file, I experience a long delay, of about 3 to 4 ...
einpoklum's user avatar
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Why doesn't strace -f work on GNOME Terminal?

I tried running the command strace -f gnome-terminal --wait |& grep write and then in the terminal window that opened, I typed ls and pressed enter. I expected to see write syscalls corresponding ...
Kerrick Staley's user avatar
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terminal: Error occurred while reset 800b: errno=25

I have an extremely bizarre problem, occurring somewhere at the intersection of terminal, su, w3m and /dev/null: when I su - from user1 to user2, following command does not work: $ w3m zz.html 2>/...
Martin Vegter's user avatar
1 vote
0 answers
192 views

Hint to investigate some SEGFAULT no longer happening when strace-ing

I get an application (webcamoid in its 8.8 version) that used to be working troublefree and which now segfaults systematically at startup (kde-plasma/X11 do not even get the opportunity to open some ...
MC68020's user avatar
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Why top is not reporting high %wa on too many write sys calls

My HTTP application suddenly started taking extra time to start up. During this phase, it loads the data from the disk to the in-memory data structure. I doubt it is due to the extensive logging ...
shubmishra's user avatar
2 votes
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183 views

Minimal c program does more system-calls than expected

I am trying to learn more about strace. I use strace to understand the calls a c program makes. The c program is: void _start () { for (;;) { } } The program gets compiled with clang -...
Koronis Neilos's user avatar
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2 answers
106 views

How is it possible that getcwd() takes sometimes half a second, according to strace?

As far as I understand it does not even touches the filesystem. So what can be a cause for this, using strace -T: 0.481441 getcwd("/home/user/web/url.com/public_html", 4096) = some ...
jsaak's user avatar
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What is the complete list of file functions equivalent to the "strace -e file" options?

According to man strace the -e file option traces all syscalls which take a file name as an argument. What is the whole set? %file file Trace all system calls which take a file ...
guronanak's user avatar
2 votes
1 answer
1k views

How do I use perf trace record?

I can use perf trace as a low-overhead replacement for strace, e.g. to trace all Apache instances: perf trace -p $(pidof apache2 | tr ' ' ',') To run the trace only for up to 10 seconds: perf trace -...
Martin von Wittich's user avatar
1 vote
0 answers
125 views

How to find all the unclosed files of a process?

I'm trying to debug if my app keeps opened files somewhere in the code. I thought of using strace for that but all of the previous topics (like this one) were talking about only opened files. While ...
vesii's user avatar
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Timing system call with ltrace: Adding `syscall` + `clock_gettime`?

I'm looking for some clarity in terms of the system calls. I tried avoiding the vDSO by calling a system call clock_gettime directly. Here is a snippet of a program named sys_clock_gettime. int clock =...
Xavier Merino's user avatar
27 votes
1 answer
7k views

root cannot write to file that is owned by regular user

I create a file as regular user testuser: $ cat > /tmp/zz the file is owned by that user (as expected): $ ls -lA /tmp/zz -rw------- 1 testuser testuser 0 Feb 20 15:32 zz Now when I try to ...
Martin Vegter's user avatar
2 votes
0 answers
271 views

Debug & analyze pthread_mutex_lock issues

I've being recently facing some hardcore issues with Mutex lock for Linux, notably MySQL, memcache & APCu. Example: SQLSTATE[HY000]: General error: 1205 Lock wait timeout exceeded; try restarting ...
Wiika's user avatar
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5 votes
1 answer
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strace top: EAGAIN (Resource temporarily unavailable)

On one of my ubuntu server, top command start very slow, when I run top command on terminal, it will display info after more than 10 seconds. Then I use strace -yy top to analysis the problem, I ...
Ren's user avatar
  • 273
1 vote
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Output redirection ownership

When i execute cat file.txt > newfile.txt, which process or program is executing the syscall? I've tried using strace cat file.txt > newfile.txt to identify this, but havent been successful in ...
Hysii's user avatar
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10 votes
1 answer
852 views

Can I skip syscalls made by the dynamic loader in strace?

When I use strace to examine a program, I often have a hard time finding where the syscalls from the dynamic loader end and the syscalls from the program begin. The output from strace ./hello where ...
jrpear's user avatar
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`mpirun -n 2 ./a.x`, the two processes was stuck by epoll_wait, why?

I run a mpi progrem with mpirun -n 2 ./a.x. However, these two processes was stuck. And it is always get stuck and seldom(actually only once) pass through. I find follow information by strace and ...
Runfeng Jin's user avatar
1 vote
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680 views

Strace displaying results in ASCII only at process ending and not runtime

I'm searching a way for strace to print the content of the write(...) syscall to ASCII and not useless bytes ! The Strace command I use : sudo strace -e write=1 -e trace=write -s9999 -p 551 2>&...
Doctor's user avatar
  • 133
1 vote
1 answer
416 views

Find the process command spawned by another process

I have a python script. This python script will attempt to execute Unix command via the system() command. I want to know what this command is. This logic is hidden very deep inside many dependencies, ...
Raven's user avatar
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3 votes
0 answers
78 views

Firefox 87.0 starts slow on Linux 5.8.0

I have upgraded firefox to 87.0 several days ago, but it starts slowly since then. It works fine after startup, but only takes more time to start. firefox -safe-mode does not speed up the startup. I ...
Simon's user avatar
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1 vote
0 answers
442 views

Linux top command hang about 25 seconds before works fine

On my Linux server, top command hang about 25 seconds before works fine: $ time top -b -n 1 Output: ... real 0m25.199s user 0m0.018s sys 0m0.014s When top command is hang, I found the ...
Ren's user avatar
  • 273
3 votes
1 answer
2k views

command 'top' and 'ps' take a long time to show result

Recently, I find when I run commands like top or ps -aux on a server, it is very slow to show the result (STDOUT). I have checked the usage of disk space, memory, and CPU, all of them are OK. After ...
Lijia Yu's user avatar
0 votes
1 answer
770 views

rmdir and rm -rf fail with Directory not empty, no hidden files; -1 EAGAIN (Resource temporarily unavailable) from strace of ls

On a RHEL 6.10 server there is a mounted NAS where I can't delete directories with neither rm -rf nor rmdir. Both fail with rm: cannot remove "backup/backup.1": Directory not empty. I made ...
RobbieTheK's user avatar
3 votes
1 answer
1k views

Strace shows that the time spent in syscalls is much longer than the total time elapsed. Why?

I am running an AI inference program based on Tensorflow-gpu. By running /usr/bin/strace -c -f /usr/bin/time ./program, I got the following output: <my program's output> 367.91user 1032.14system ...
Azuresonance's user avatar
7 votes
2 answers
5k views

How can I use strace on a command executed as a specific, non-root user?

I'm trying to use strace to observe where a certain process searches for files. The locations this process searches will differ depending on the user and their unique environment variables. However, ...
duggulous's user avatar
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1 vote
1 answer
856 views

strace calls from running process and count them

I have a background process that will run for many many hours. I would like to trace and count the number of write calls live. sudo strace -p27861 -s50 -e write It gives me lines like this: write(1, ...
777moneymaker's user avatar
0 votes
1 answer
2k views

What is the meaning of this strace message?

My program is crashing after some time on Ubuntu 18.04 and the last few lines of strace are like this: 6260 openat(AT_FDCWD, "/usr/share/locale/en_US.UTF-8/LC_MESSAGES/libc.mo", O_RDONLY) = ...
TonySalimi's user avatar
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0 answers
316 views

What is the best way of finding library conflicts in a large application?

I have a large application (let's call it P) with lots of dependencies to boost, Qt, zlib, libpng, etc. Recently, I have added a feature to P that needs to dynamically load a new shared object (let's ...
TonySalimi's user avatar
2 votes
1 answer
15k views

How to install libicui18n.so.58 on Ubuntu 18.04?

While running my application on Ubuntu 18.04, it fails. Using the trace command, I found that one library is missing on my machine: user@user-Box:~/Debug$ strace -o log -f ./test_project ./...
TonySalimi's user avatar
2 votes
1 answer
184 views

strace and polkit

I have a program who refuse to run as root, he wants the "true user" to run it, but he wants privilege escalation during the execution to modify some protected paths With strace it's okay as ...
wxi's user avatar
  • 149
-5 votes
2 answers
162 views

Hunting for a malware

I'm hunting a malware under my linux .mozilla folder. My first step is try to log all opened files during running of firefox. What do you advice me to use for this purpose ? Strace ? Are there other ...
Lews's user avatar
  • 166
3 votes
2 answers
1k views

sshd disconnects after unknown syscall

I'm working on an embedded system (based on a Cortex-A8 CPU) running Linux kernel 4.19, OpenSSH_8.3p1, OpenSSL 1.1.1h, glibc 2.32, compiled with GCC 10.2 using buildroot. When a client tries to ...
awagner's user avatar
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0 votes
1 answer
332 views

get pids/locks for lvm - source for opencount on dmsetup info

# dmsetup info Name: ubuntu--vg-root State: ACTIVE Read Ahead: 256 <---- cat /sys/dev/block/253:0/bdi/read_ahead_kb gives 128 not 256 Tables present: LIVE Open ...
user5844653's user avatar
19 votes
2 answers
38k views

Write strace output to a file

I'm trying to write the output of strace ls to a file. I know that I need to use > in order to forward output of a command to a file, but it doesn't work. It creates a file but the command prints ...
yeled zevel's user avatar
2 votes
1 answer
90 views

grep does not colorize properly

I am trying to pipe a output from command to grep. $ strace a.out | grep --color=always "mmap" but it only outputs non-colorized output of strace: ... mmap(NULL, 503808, PROT_READ|...
milanHrabos's user avatar
0 votes
1 answer
100 views

I seem to be getting strace info on every bash command. How do I stop it?

This is what I get when I type ls in a terminal: (It doesn't happen when I login as root. Only when I am the js user. js@hp-suse-laptop:~$ ls 7255: 7255: file=libselinux.so.1 [0]; ...
jschwartzman's user avatar
1 vote
1 answer
791 views

how to keep stty sane after piping strace to vim?

this makes vim madness: $strace -o >(vim -; stty sane) file.out; stty sane I have typed stty sane in processed substitution as well as in next command but none of them did their job. Once i piped ...
Herdsman's user avatar
  • 340
1 vote
1 answer
2k views

strace reports a system call which is taking too long

The problem The following code snippet shows the time it took to my system to open inkscape plus the time it took to me to immediately close the inkscape window. $ /usr/bin/time -p inkscape real 26....
gfe's user avatar
  • 191
1 vote
0 answers
1k views

Linux Executable fails to run with error “/usr/bin/strace: exec: No such file or directory” on running strace

I need to analyse linux binary executable file using strace for capturing the system calls. On running the command: /usr/bin/strace ./005f32fffe1da3bc100e7dcd8b2f8f2c I got this error: execve("./...
mmg's user avatar
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