File Permissions

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


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

System Info:

I have normal user in CentOS 7 whose name is "mostafa" (the name of the account).

I naturally have another user called root with all privileges. User "mostafa" is put into sudoers file, too.

The OS is installed in VmWare, so the system is all mine.

Problem:

Now I create a file with touch file.sh and put a command in it, but when I want to run it with Code:
sudo ./file.sh

, an error is shown that the command Code:
./file.sh

does not exist. But if I Code:
 sudo chmod 777 ./file.sh

then it gets run. My question is that, why should I use Code:
chmod 777

when I myself have created the file, and I am in sudoers.

Can anyone explain me why shuold I still use Code:
sudo chmod 777

when the creator of the file is me.

Setuid, Setgid, Sticky Bit

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).

I Need To Setup Kyless Ssh Between CentOS And HP-UX Both Ways

I have 2 linux boxes Code:
HP-UX server1 B.11.11 U 9000/800

and Code:
 CentOS release 6.3 (Final)

I need to setup a password-less ssh. I could login from HP-UX to cent os but not other way.

Is it possible to use password less ssh both ways ? Is there any extra step in HP to setup keygen?

what I am doing

Code:
ssh-keygen -t rsa

copy the ~/.ssh/id_rsa.pub from client machine to ~/.ssh/authorized_keys on server machine

/usr/lib/libgconf2-4/gconf-sanity-check-2 Exited With Status 256

Here is the problem:
/usr/lib/libgconf2-4/gconf-sanity-check-2 exited with status 256

Here are all the solutions I founded on the internet (NONE of them work):
rm -rf /var/tmp/rc_host_0
chown -rwx root:root /tmp
chmod 1777 /tmp
chmod 0755 /home
chmod a+rwx /tmp
chown -R root:root /var/lib/gdm
chmod -R 777 /var/lib/gdm
rm -rf /var/lib/gdm3/.*
rm -rf /var/lib/gdm/.*
rm -rf /Home Dir/UserName/.gcon*
rm -rf /Home Dir/UserName/.gnom*
rm -rf /Home Dir/UserName/.cache
rm -rf /Home Dir/UserName/.person*
touch /Home Dir/UserName/.personal.login
cat /etc/gconf/gconf.xml.system
mkdir -p /usr/local/etc/gconf/gconf.xml.default
chmod 775 /etc/gconf/gconf.xml.system

Here is my system information:
Linux Kernel v2.6.32-504.12.2.el6.x86_64
CentOS 6.6
GNOME 2.28.2

I have been searching for an answer all week and found NONE.
Somebody, Anybody please help!!!

The only solution I found that works is deleting all the .files, but there's got to be a better way.

Permission Denied When Trying To Execute An Application On A SD Card

Hi,
I made some little applications with qt creator and i wanted to run them on an embedded linux board (linux 2.6.24). To transfer the files i use a SD card. If i move the applications to "/bin" after having mounted the SD card and then "chmod a+x" them then i have no problem running them.
But if i mount the SD card and try to run the applications directly in the folder where i mount it i have an error : "Permission denied". Also when using the command "ls" i notice that if i keep the files in the mounting folder and try to "chmod a+x" them, the modification don't happen. They stay "greyed" and don't go "green". (I don't know if this color code is a standart for linux terminal but maybe this could help you understand the problem).
When mounting the SD card i use the command :
Code:
mount -t vfat /dev/mmcblk0p1 /mnt/SD

So the files are located in /mnt/SD.

Am i missing something or is it not possible to run something like that ?

EDIT :
I tried "mount -t vfat -o umask=0000 /dev/mmcblk0p1 /mnt/SD" to chnage how i am mounting the SD card.

Still "Permission Denied".

With "ls -l" i can see that the permissions are staying :
-rw-rw-rw-

Even if i try something like "chmod 777".

It seems to be a problem related to the fact that the sd card is formated as fat32 but it must stay like that.

Can Not Add Ecdsa Key To Ssh-add

OpenSSH_6.7p1, OpenSSL 1.0.1f 6 Jan 2014

I am having trouble adding a ecdsa key to ssh-add
However, I can add a rsa key without problem.

My file permissions:
Code:
id_ecdsa miati:miati-600
id_ecdsa.pub miati:miati-644
id_rsa miati:miati-600
id_rsa.pub miati:miati-644
/home/miati/.ssh/ miati:miati-700

When I try to add rsa & ecdsa

Code:
$ ssh-add id_rsa
Enter passphrase for id_rsa: 
Identity added: id_rsa (id_rsa)
$ ssh-add id_ecdsa
Enter passphrase for id_ecdsa: 
Error reading response length from authentication socket.
Could not add identity: id_ecdsa

My command to create each key

Code:
ssh-keygen -t rsa -b 4096
ssh-keygen -t ecdsa

Please Interpret The Meaning Of This Command

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

Kill -3 Pid > /tmp/process.txt Not Working?

Hi All,
I am trying to get a dump of a process using kill and it doesn't look to be working, can someone explain what I am doing wrong?

Code:
systemctl start snmpd.service

Code:
pgrep snmpd
4233

Code:
kill -3 4233 > /tmp/snmp_pid.txt

OR

Code:
kill -SIGQUIT 4233 > /tmp/snmp_pid.txt

Yes the process quit's which is fine but there is no output from the process in /tmp/snmp_pid.txt.

Can someone please explain?

Thanks

Sharing Folders And Mounting Shares With SetGID / Samba

OK this is kinda long, so I will shorten it as much as I can, as to not be long-winded.

My current network at home:
1 - CentOS 7 desktop (server)
1 - Ubuntu 14.04 desktop
1 - Fedora 21 laptop
2 - Windows 7 desktops
some other various windows boxes also that don't get used regularly, but are on the network.

My 2 Linux desktops (which I use as servers, but they really aren't) have shared folders on them, which I share to the network via Samba (CIFS). I use Samba because Linux is smarter than Windows and Windows won't read NFS, so I share them as Samba so all devices can see them.

Generally speaking, if I share the folders on each box as 0777, I have no issues. But lately I have been wanting to implement some better security, so I wanted to SETGID and chown the shared folders from the local machine to a specific group, then change the folders to 2774.

My problem is that I keep getting permissions errors when trying to connect from the other Linux machines, and sometimes the Windows machines also. My main question is: do I CHMOD 2774 the local mount-point before mounting it? Or so I CHMOD 2774 the shared folder on the other server, then mount it locally to a folder whose permissions are different? Or do I CHMOD both of them the same?

basically the uis and gid ownerships change on a local folder when I mount a shared drive to that folder, so when I try to write or sometimes read that local folder, I get permissions errors.

I can provide any additional info needed.

What Is The Rsync Flag To Ignore Permissions

I am using Rsync to backup files to a another machine, the users on my fileserver do not exist on the backup server so Rsync throws errors about the permissions. It copies the files fine but I want to get rid of the errors and have Rsync ignore the permissions when backing up.

/backup is a mounted ftp directory

Below is the current command and output:
Code:
root@Fileserver:~# rsync -av --delete /shared/fileshare/ /backup/backup
building file list ... done
created directory /backup/backup
./
manager/
manager/chironfs.txt
manager/cronman.txt
manager/curlftpfs.txt
manager/curlman.txt
manager/getnetaddress.txt
manager/grepman.txt
manager/rsyncman.txt
manager/tarman.txt
public/
user1/
user10/
user2/
user3/
user4/
user5/
user6/
user7/
user8/
user9/
rsync: chown "/backup/backup/manager/.chironfs.txt.c6MbJ7" failed: Operation not                  permitted (1)
rsync: chown "/backup/backup/manager/.cronman.txt.hdBG4P" failed: Operation not                  permitted (1)
rsync: chown "/backup/backup/manager/.curlftpfs.txt.t1sG4L" failed: Operation no                 t permitted (1)
rsync: chown "/backup/backup/manager/.curlman.txt.6oWPoW" failed: Operation not                  permitted (1)
rsync: chown "/backup/backup/manager/.getnetaddress.txt.V8z8Kk" failed: Operatio                 n not permitted (1)
rsync: chown "/backup/backup/manager/.grepman.txt.REh4WW" failed: Operation not                  permitted (1)
rsync: chown "/backup/backup/manager/.rsyncman.txt.ho8VNM" failed: Operation not                  permitted (1)
rsync: chown "/backup/backup/manager/.tarman.txt.BkcmeS" failed: Operation not p                 ermitted (1)

sent 211115 bytes  received 274 bytes  6710.76 bytes/sec
total size is 210263  speedup is 0.99
rsync error: some files could not be transferred (code 23) at main.c(977) [sende                 r=2.6.9]
root@Fileserver:~#

I tried the flag to adding the no flag to -p but it still didn't work, see below:
Code:
root@Fileserver:~# rsync -av --no-p --delete /shared/fileshare/ /backup/backup
building file list ... done
./
manager/
manager/chironfs.txt
manager/cronman.txt
manager/curlftpfs.txt
manager/curlman.txt
manager/getnetaddress.txt
manager/grepman.txt
manager/rsyncman.txt
manager/tarman.txt
public/
user1/
user10/
user2/
user3/
user4/
user5/
user6/
user7/
user8/
user9/
rsync: chown "/backup/backup/manager/.chironfs.txt.6Q3eP2" failed: Operation not permitted (1)
rsync: chown "/backup/backup/manager/.cronman.txt.FC8Orx" failed: Operation not permitted (1)
rsync: chown "/backup/backup/manager/.curlftpfs.txt.mlVSN9" failed: Operation not permitted (1)
rsync: chown "/backup/backup/manager/.curlman.txt.vlJ4b1" failed: Operation not permitted (1)
rsync: chown "/backup/backup/manager/.getnetaddress.txt.LXmft0" failed: Operation not permitted (1)
rsync: chown "/backup/backup/manager/.grepman.txt.SVuaye" failed: Operation not permitted (1)
rsync: chown "/backup/backup/manager/.rsyncman.txt.KTNYqA" failed: Operation not permitted (1)
rsync: chown "/backup/backup/manager/.tarman.txt.zcU90c" failed: Operation not permitted (1)

sent 211115 bytes  received 274 bytes  7686.87 bytes/sec
total size is 210263  speedup is 0.99
rsync error: some files could not be transferred (code 23) at main.c(977) [sender=2.6.9]