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strange behaviour for strace -f

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http://www.linuxquestions.org – Ran into a weird situation I had not seen before while using strace -f command I had to strace my 'passwd' command since I needed to debug something. But 'strace -f -o /tmp/file passwd' command failed to run eraser@viper-laptop:~$ strace -f -o /tmp/passwd1 passwd Changing password for eraser. (current) UNIX password: passwd: Authentication token manipulation error passwd: password unchanged If I drop -f option it works fine. I am using Ubuntu 10.4(Lucid Lynx), recently switched from fedora to ubuntu. Any idea what could be the issue ?? (HowTos)

xskl's picture
Submitted by xskl on 09/07/2010

Stories similar to strange behaviour for strace -f

Messed up password 36 weeks 6 days ago

I am unable to change my password even in root (recovery mode), or to unlock it. I can still access my account, but without password protection.

I am unable to change my password even in root (recovery mode), or to unlock it. I can still access my account, but without password protection.

I forgot my Ubuntu password so I booted into recovery and dropped into a root shell prompt and this is what happened:

root@username-PC:~# passwd username Enter new UNIX password: Retype new UNIX password: passwd: Authentication token manipulation error passwd: password unchanged

I had tried method in recovery mode.

passwd myusername

then getting new password I typed the new password twice

passwd:Manipulation Token Authentication Error passwd:password unchanged

Please help me change my password.

I'm currently fascinated by strace so, being new to it, I decided to play around a little. As suggested by the question title, I tried both strace su and strace ssh. Both commands displayed the password I typed in the strace output. su kept complaining of an incorrect password while ssh managed to log in normally. My questions:

Is this a security flaw or am I missing something?

I am user xyz on redhat linux VM abc.

I cannot change password.

abc:/home/xyz>passwd Changing password for user xyz. Changing password for xyz (current) UNIX password: Password changes on the command line are not supported.

What is strace command? 3 years 3 weeks ago

strace is a debugging command in Linux to monitor the system calls used by a program and all the signals it receives, similar to truss command in other Unix systems. The most common usage is to start a program using strace, which prints a list of system calls made by the program.

Published at LXer:

Having trouble figuring out why Apache isn't starting, or another program is crashing and burning, and the logfiles are giving no clue? Time to reach for strace. What's strace? The strace utility is used to run a command and display its system calls, so you can see exactly what the program is doing until it exits.

piping strace to grep 35 weeks 6 days ago

I'm trying to run strace trough ccze, and the pipe doesn't work as expected.

The command-line I'm running to test is sudo strace -p $(pgrep apache2) | grep open, and all lines are output, ignoring grep.

Is there something special about strace that causes this behavior?