Why Should I Always Use Chmod When Not As A Root User

There's something really weird happening with permissions on a directory in linux. I have the directory /dir

Code:

ls -ld /dir
drwxrwxrwx. 2 root root 4096 Jan  8 00:06 dir
chmod 2777 /dir [this sets the setgid bit on]
ls -ld /dir
drwxrwsrwx. 2 root root 4096 Jan  8 00:06 /dir

And this is what I expect it to do.
However, when I change it to setid (WITHOUT setgid), it simply doesn't work. Instead of overwriting, it cumulates:
Code:

chmod 4777 /dir [for setting setuid bit on]
drwsrwsrwx. 2 root root 4096 Jan  8 00:06 /dir

As you can see, the setgid bit is still on together with the setuid! However, if I run:
Code:

chmod -s /dir

then the file has a 0777 permission.

And then again, if I change its permission to 4777 (so setuid):
Code:

chmod 4777 /dir
drwsrwxrwx. 2 root root 4096 Jan  8 00:06 /dir

it acts normally. So the same chmod 4777 acts differently in two different contexts.

I really can't understand it. Basically, I cannot get rid of the setuid/setgid through binary permissions. The sticky bit works fine. Changing from 1777 to 0777 adds and removes "t" respectively. What am I to make of all this? This behaviour makes no sense to make especially given that we can change the permissions to 6777 (setuid + setgid).

Hi, I've just recently installed MySQL connector/c from source code on my Slackware 14.1 x64

I read the official instructions of the connector but I felt a bit disorientated when I read:
Code:

1 -Change location to the top-level directory of the source distribution.

I interpreted that I have to go to the "highest" directory Code:

/

So I wrote: Code:

 
        #                            cd /

root@- /#                            tar xzvf /home/normal/Downloads/mysql-connector-c-6.1.6-src.tar.gz 

root@- /#                            cd /mysql-connector-c-6.1.6-src/

root@- /mysql-connector-c-6.1.6-src# cmake -G "Unix Makefiles"

root@- /mysql-connector-c-6.1.6-src# make 

root@- /mysql-connector-c-6.1.6-src# make install

Then I did:
Code:

ln -s /usr/local/mysql-5.6.25/include /usr/include

But when I try to compile a program in c with #include <mysql.h> i get this error:
Code:

# gcc ctemp.c 
In file included from ctemp.c:2:0:
/usr/include/mysql.h:57:27: fatal error: mysql_version.h: No such file or directory
 #include "mysql_version.h"
                           ^

What can I do? Thanks a lot and sorry for poor english

PD: If you need the official instructions I paste here the link: https://dev.mysql.com/doc/connector-...on-source.html

I am trying to learn how to set up Authentication Keys to log in to my server.

Could someone please explain what the following code does...
Code:

chown -R example_user:example_user .ssh
chmod 700 .ssh
chmod 600 .ssh/authorized_keys

Thanks,


Rob

Dear all,

This is long story cut short, with vsftp, if i set this parameters in the vsftp.conf file below

Code:

local_enable=YES
chroot_local_users=YES

I am able to login to the ftp account, see and list my home/user directory, and if i do a cd / or cd .. , i will still be chroot to my /home/user directory.

without, the need to chmod or or chown anything to my /home/user directory

=============================================

With openSSH, internal_sftp, even though I have set the sshd_conf to

Code:

Match user alankoh
X11Forwarding no
AllowTcpForwarding no
ForceCommand internal-sftp
ChrootDirectory /home/%u

I will need to change owner my /home/user directory to have root becomes it owner.
============================================

Q1) why this difference ? How does vsftp chroot without changing the /home/user folder ownership ?

Q2) i realize that openssh ChrootDirectory parameter causes my default login directory to be set as that of the parameter.
(e.g. if i set to "/whatever/xyz", i will be brought to that /whatever/xyz everytime i login to the sftp instead of my /home/user folder.

Why ? I thought that ChrootDirectory is just a security measure to specify the directory to go to in case the user cd to root (e.g. cd /), else not, i should still go to my /home/user folder everytime i login to sftp.

Regards,
Noob

Hello,

I try to use a ftp daemon and a Telnet daemon with inetd and the BusyBox v1.19.0 on a linux 2.6.24.

When running inetd and then checking what is listening with "netstat -an |grep LISTEN" i have :
Code:

netstat: /proc/net/tcp6: No such file or directory
netstat: /proc/net/udp6: No such file or directory
netstat: /proc/net/raw6: No such file or directory
tcp        0      0 0.0.0.0:80              0.0.0.0:*               LISTEN

tcp        0      0 0.0.0.0:21              0.0.0.0:*               LISTEN

tcp        0      0 0.0.0.0:23              0.0.0.0:*               LISTEN

ftp port 21 and Telnet port 23 seems to be listening.

My inetd.conf file is :

Code:

#<service_name>    <sock_type>    <proto>    <flags> <user>     <server_path>     <args> 

21 stream tcp nowait root ftpd ftpd /etc
telnet            stream        tcp        nowait    root    /usr/sbin/telnetd

I have no rule in my hosts.deny so nothing should be stopped and i have no iptables firewall in place too.

When typing "ftp://ipofthetarget" in a web browser i have a error :

Code:

504 Gateway Timeout
Gateway timeout expired while waiting for server response.

And when trying to Telnet from another computer or "Telnet localhost" from the board i have :
Code:

# telnet 10.2.29.201
Trying 10.2.29.201...
connected to 10.2.29.201.
Escape character is '^]'

Connection closed by foreign host.

This would mean that the connection for Telnet exist but why is it closing ?

Thank you for your future answers !

UPDATE 1 :
If i try to run telnetd like this :
/usb/sbin/telnet -l /bin/sh
i can connect anonymously from another computer, not perfect because i would like a user/password but still of use.
The problem with the ftp daemon still exist.

UPDATE 2 :
Trying from Windows cmd or linux terminal : ftp ipofthetarget seems to work
Not perfect because i would like a user/password too but still of use.

I am still open for suggestion for the user/password thing. I am not deleting the thread in case someone interested about this exist.

I am trying to convert a PDF document from an Excel and PowerPoint document. I installed it and ran the command. It gives no warning.. Just doesn't create a new PDF document. I've successfully done this before, but I think it was a different server. I've checked file permissions, but don't think it is the issue (I've tried as a normal user and as root).

I could convert doc, docx, and txt files, but not xls, xlsx, ppt, and pptx files.

Thoughts why? Is there a verbose option or a log file which I could check for clues?

Thank you


Code:

yum -y install libreoffice-headless libreoffice-writer

Code:

Package 1:libreoffice-headless-4.0.4.2-14.el6.x86_64 already installed and latest version
Package 1:libreoffice-writer-4.0.4.2-14.el6.x86_64 already installed and latest version

Code:

libreoffice --headless -convert-to pdf myfile.xlsx

I'm trying to install a tar file and as root, when I use the following tar commands

Code:

tar -xvfp file.tar

or 

tar -xf file.tar

For some reason, it strips out the user id and group id and replaces with the the following numbers: 544 for UID and 400 for GID.

Also, from what I'm reading, it looks like tar preverses permissions from one server to another, which I didn't know.

Because of this, I can't install this file, is there a way around this?

thanks

I'm running LinuxLite 2.0 32bit on a Dell 3000.

I have never come across anything like this and to tell you, I am stumped.

Here are the contents of my crontab file:

Code:

# Edit this file to introduce tasks to be run by cron.
#
# Each task to run has to be defined through a single line
# indicating with different fields when the task will be run
# and what command to run for the task
#
# To define the time you can provide concrete values for
# minute (m), hour (h), day of month (dom), month (mon),
# and day of week (dow) or use '*' in these fields (for 'any').#
# Notice that tasks will be started based on the cron's system
# daemon's notion of time and timezones.
#
# Output of the crontab jobs (including errors) is sent through
# email to the user the crontab file belongs to (unless redirected).
#
# For example, you can run a backup of all your user accounts
# at 5 a.m every week with:
# 0 5 * * 1 tar -zcf /var/backups/home.tgz /home/
#
# For more information see the manual pages of crontab(5) and cron(8)
#
# m h  dom mon dow   command
*/10 * * * * /usr/bin/arecord -t wav -f cd -d 42 /home/randy/Music/lanting$(date "+\%^b\%d\%y").wav

If I run this from the terminal, everything is fine. It properly records the audio:

Code:

/usr/bin/arecord -t wav -f cd -d 42 /home/randy/Music/lanting$(date "+\%^b\%d\%y").wav

If I run this as it is shown in my crontab file, it records but there is no audio recorded.:


Code:

*/10 * * * * /usr/bin/arecord -t wav -f cd -d 42 /home/randy/Music/lanting$(date "+\%^b\%d\%y").wav

What could be causing this? I tried different cron settings for example 15 14 * * 2

This recorded at 2:15pm on Tuesday (today) but no audio. Yet if I run the code as mentioned above, from the terminal without the cron settings, the recording is fine.

Any ideas what I should do?

Hi ,

Please explain what the below command means ..


Code:

if grep -c -i Y $INIFILE > /dev/null

I know what is the use of grep, it is used for finding a character or string in a file. But i could not understand the above form of grep command.

I am new to linux so this might be a simple question, but please throw some light on it.


Edited

And also please explain why they are creating a file in null in the below command

Code:

cat /dev/null > $DATA_DIR/$DATAFILE

https://code.google.com/p/wavelet1d/...ar.gz&can=2&q=

The above link is where I downloaded *.cpp(s) and the libraries.

If you "untar" the package, in "examples" directory, there are some demonstration files. What I wanted to do was to make an executable file out of "wavedemo1.cpp".

I modified the code in "wavedemo1.cpp"; Code:

#include "wavelet2d.h"

to Code:

#include "wavelet2s.h"

, then placed the header file "wavelet2s.h" (from /wavelib/src/linuxstatic) and the modified "wavedemo1.cpp" into my working directory.

Inside the working directory, I ran the following command

Code:

gcc -L/home/mario/wavelet/wavelib/linuxstatic -lwavelet2s wavedemo1.cpp -o wavedemo1

Then I get the following error messages.

/usr/bin/ld: skipping incompatible /home/mario/wavelet/wavelib/linuxstatic/libwavelet2s.a when searching for -lwavelet2s
/usr/bin/ld: cannot find -lwavelet2s
collect2: error: ld returned 1 exit status

I'm not sure what went wrong with my approach. This is my first time trying to use libraries on linux and it's giving me really tough times.

I would appreciate your help, please let me know if you need more details to explain things.

Thanks.