different questions

[p3dRo]

Hi, Im learning myself to secure a hardware with linux running. I have now several questions, I wait you can help me

1. Why there is a line with user in the shadow file when the passwd file doesn-t show user???

# cat passwd
root:0:0:Root,,,:/:/bin/sh
admin:0:0:Admin,,,:/:/bin/sh

# cat shadow
root:sdfdfsdffs:::
admin:sdfdfsdffs:::
user:sdfdfsdffs:::

2. Is there a log file where I can see all the programs that are installed like firefox, amsn, etc ???

3. I wonder where is stored the icon of a program, for example, mozilla firefox.

4. What does it mean to see a "core" in the filesystem like this:

-rw------- 1 root root 255136 Mar 24 14:12 core

Thanks,
p3dRo

[i92guboj]

Hi, Im learning myself to secure a hardware with linux running. I have now several questions, I wait you can help me

1. Why there is a line with user in the shadow file when the passwd file doesn-t show user???

# cat passwd
root:0:0:Root,,,:/:/bin/sh
admin:0:0:Admin,,,:/:/bin/sh

# cat shadow
root:sdfdfsdffs:::
admin:sdfdfsdffs:::
user:sdfdfsdffs:::

I never looked too deep into this, but as far as I can tell you: there shouldn't be a reason for that. Each entry in passwd matches an entry in shadow, and only one.

2. Is there a log file where I can see all the programs that are installed like firefox, amsn, etc ???

This depends on your distro. Usually, the package manager for your distro is that one that can give you this information.

3. I wonder where is stored the icon of a program, for example, mozilla firefox.

It depends on the distro as well. But usually, specific icons are stored under /usr/share/icons. Icons themes for kde can be stored in subdirs there are well, but they are usually stored on the folder where you installed kde. In some distros this is under /opt/kde.../share/icons or /usr/kde/3.5/share/icons or whatever.

Again, the package manager for your distro can probably show where the files for a given package reside on your hd.

4. What does it mean to see a "core" in the filesystem like this:

-rw------- 1 root root 255136 Mar 24 14:12 core

Thanks,
p3dRo

Core dump files are created by your kernel and contain debug info. So, if you are not using a debugger for anything, then you don't need those. This feature can be disabled when configuring your kernel, before compiling it. But if you are using a precompiled kernel that was installed by your distribution, just ignore them.

You can delete all the core files in your home with this command:

find $HOME -name core -exec rm -f {} \;

You can also virtually disable this feature using this:

ulimit -c 0

That works only under bash (if you don't know what shell you are using, you are *probably* using bash). The bad thing is that it's not permanent. To make it permanente, just add that line into ~/.bashrc and ~/.bash_profile, then close all the sessions, and login again.

From now on, you shouldn't get any more core dumps.