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Linux Security

The Linux operating system, in all its flavors, has its own share of security flaws that allow intrusions, but there are various mechanisms by which these flaws can be removed, generally divided into two parts: authentication and access control. Authentication is responsible for ensuring that a user requesting access to the system is really the user with the account, while access control is responsible for controlling which resources each account has access to and what kind of access is permitted.

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I am getting this error message, when I was trying to run rpmbuild --rebuild lin_tape-3.0.23-1.src.rpm on Red Hat Linux 7.4 (Kernel version: 3.10.0-693.1.1.el7.x86_64). Can some one let me know what is problem and what should be the proper procedure to fix it. Here is the output mentioned below,

#rpmbuild --rebuild lin_tape-3.0.23-1.src.rpm
Installing lin_tape-3.0.23-1.src.rpm
Executing(%prep): /bin/sh -e /var/tmp/rpm-tmp.sCvFVM
+ umask 022
+ cd /root/rpmbuild/BUILD
+ cd /root/rpmbuild/BUILD
+ rm -rf lin_tape-3.0.23
+ /usr/bin/gzip -dc /root/rpmbuild/SOURCES/lin_tape-3.0.23.tgz
+ /usr/bin/tar -xf -
+ '[' 0 -ne 0 ']'
+ cd lin_tape-3.0.23
+ /usr/bin/chmod -Rf a+rX,u+w,g-w,o-w .
+ exit 0
Executing(%build): /bin/sh -e /var/tmp/rpm-tmp.KGligF
+ umask 022
+ cd /root/rpmbuild/BUILD
+ cd lin_tape-3.0.23
++ echo x86_64-redhat-linux-gnu
++ cut -f 1 -d -
+ p=x86_64
+ '[' x86_64 == i386 ']'
+ '[' x86_64 == i586 ']'
+ '[' x86_64 == i686 ']'
+ '[' x86_64 == ppc64 ']'
+ '[' x86_64 == powerpc ']'
+ '[' x86_64 == powerpc64 ']'
+ '[' x86_64 == s390 ']'
+ '[' x86_64 == s390x ']'
+ '[' x86_64 == ia64 ']'
+ '[' x86_64 == x86_64 ']'
+ proc=AMD
+ make KERNEL=3.10.0-693.1.1.el7.x86_64 PROC=x86_64 SFMP=0 driver
make: Nothing to be done for `driver'.
+ exit 0
Executing(%install): /bin/sh -e /var/tmp/rpm-tmp.hQeoFx
+ umask 022
+ cd /root/rpmbuild/BUILD
+ '[' /root/rpmbuild/BUILDROOT/lin_tape-3.0.23-1.x86_64 '!=' / ']'
+ rm -rf …

How to Make The Text Cursor Automatically when i'm on console text ?
I use directly on boot the tty console and desactivate graphical mode.

Thanks for your reply,

someone talk me about : /etc/inittab, or /etc/fstab
But i don't think it's good idea to modify 2 by 5
I’m having trouble setting up LUKS on a Red Hat Test Server. I decided not to have a DEV prompt for a passphrase at boot but to use manual decryption instead. This is supposed to require execution of the cryptsetup commands and mounting. I attempt to set it up on a blank second disk I recently installed. Here’s the session…


sudo cryptsetup luksOpen /dev/sdb crypt-sdb
# enter /dev/sdb password

sudo cryptsetup luksClose /dev/sdb crypt-sdb


This then caused RHEL to freeze and force a cold reboot. I then used yum to run updates. I try again…


sudo cryptsetup luksOpen /dev/sdb crypt-sdb
# enter /dev/sdb password
#[<username>@localhost dev]$ sudo cryptsetup luksClose /dev/sdb crypt-sdb
Device sdb not found

# [<username>@localhost dev]$ sudo mount /dev/sdb
mount: can't find /dev/sdb in /etc/fstab


So I attempt to enter /dev/sdb in /etc/fstab but unsuccessful since it’s read-only. I try this.


[<username>@localhost etc]$ sudo cryptsetup luksFormat /dev/sdb
[sudo] password for <username>:

This will overwrite data on /dev/sdb irrevocably.

Are you sure? (Type uppercase yes): YES
Enter passphrase:
Verify passphrase:
Cannot format device /dev/sdb which is still in use.
[<username>@localhost etc]$ sudo umount /dev/sdb
umount: /dev/sdb: not mounted
[<username>@localhost …
Hi Experts
i need to disable ubuntu desktop 17.10  GUI and startup with command or tty only
i googled for this and i found that i need to run this command
sudo systemctl stop lightdm.service
but i got error the lightdm is not available
Hello Folks,

does anybody have any idea on how to remove/hide Places from the top panel?

Thanks for looking

I am looking for some test cases I can include in a virtual network to create rules that can make sense in an office scenario, like prohibiting social media, proxies, etc. Any ideas are appreciated, so that I will apply rules according to a particular test case. Any difficulty level, and the more original they are, the better!

Thanks in advance
I recently installed LAMP, then set up virtual sites by running sudo mkdir example.com.

I don't remember if I did this from root or from my limited user account.

When I log into SFTP from my limited user account it says permission denied in my FTP client.

Is this because I created the directories from the root account?

is it safe to be able to read and write files from a limited user account?

What command should I run to set the proper permissions?

I installed a password program on  Linux Ubuntu and have been away from this computer for about six months and of course forgot my login password (my Super user I remember). I have almost no knowledge of computers can someone walk me through the process of getting past it to get back on that thing? Or do i light it on fire?? (I don't really want to light it on fire, lol). and there are some important docs on there.
I have this issue where non-root (ie non-priv) UNIX users or even applications could
alter or create files that are world-writable & this will easily become an audit issue.

As the creator/owner, they can always change the file permission using chmod.
"umask" can set the default settings for files created but this will not stop them
from altering it subsequently.

Can provide sample ACLs or any method such that even owners of files can't alter
the UNIX file permission?

Is there any way without using paid products (OpenSource is fine) to alert us if
file permissions are being changed?  Sort of File Integrity Monitoring but we
don't want to be alerted/notified if file content or dates are changed, only if
permission is changed.

We run Solaris 10 & 11 (both have ACL features) & AIX 6.x/7.x and RHEL 7.x.

Or is there a "find ..."  command which we can run daily to identify which files'
permissions got changed the last 1 day?
We have a vendor who has put his linux based appliance behind a firewall. If I ssh to the system from the same subnet as the linux appliance ssh succeed - giving me a login prompt and then succeeding with authentication. If I login to the linux appliance from the Outside of the firewall the conversation succeeds apparently - I get a login prompt. But when I enter the same credentials the connection is promptly terminated. If I look at the firewall I see only the allowed SSH session and no other denies to the server.
Any idea what might be going on? What logging could be looked at on the linux appliance to give us insight as to why the ssh connection is failing in the second case? Thank you

I connnected to one production inace went to the log directory where bunch of log files there.

how to continuosly monitor logs for any possible errors , exceptions.

how frequently new files created?
do i have to do vi command to open the log file

please advise
On SLES 12.2 I do the following as root user:

mkdir -p /some/directory/ramdisk
chown -R simpleuser:users /some
chmod 777 /some/directory
chmod 777 /some/directory/ramdisk

Open in new window

Then I add this to /etc/fstab:
ramfs /some/directory/ramdisk ramfs defaults 0 0

Open in new window

followed by
mount /some/directory/ramdisk

Open in new window

What I expect is a ramfs mounted to /some/director/ramdisk, owned by simpleuser and users, with permissions set to 777.

Surprisingly, after rebooting the machine, the owner of /some/director/ramdisk is root:root, and the permissions have changed to something more restrictive. I deem that more of a feature  than a bug, but that behaviour is really annoying in the environment I use it in.

Currently I do an explicit change of ownership and permissions prior to starting the application that uses the ramdisk (in the respective script, with sudo), but I deem that not very elegant.

Any hint what causes the changes, and how to prevent them ?
our lab recently has a new Ubuntu (14.04.1) machine but many of software package is out of date.
I try to update it before upgrade to Ubuntu 16.04. However, there is always problems for the command "sudo apt-get update"

I have googled this problem and change "/etc/apt/sources.list" several times, but the error still exists.
I am thinking the error may come from => Could not resolve 'hcapxb01'
I have no idea about the 'hcapxb01'.  My machine has internet connection but I can't ping or nslookup the  'hcapxb01'

Experts, please help me to slove "sudo apt-get update" error. Thank you
to learn unix and its command what are best online site, learning videos, training sites that are free available out there including some books.
please advise

i have log directory with say 40 log files in it

i have to search on "NullPoinerException" on above files and find out which file has this exception and which line

how do i grep this?

can i do these kinds of things on winscp etc some gui tools rather than putty?

In below grep command

grep -C20 command "session" fileName

what is meaning of -  and C and 20.
 please advise

how to import saved ssessions  from putty to mputty.(i saved about 50 sessions with names like integration, systest, prod1 etc in putty which i want to transfer over to mputty without again typing host, port saved session nae etc)

How to point mputty to use putty and get data from putty?
please advise
CIS has hardening guides for various Windows, UNIXes and Cisco switches/routers.
There are hardening guides for Juniper as well.

Now our Audit wants a hardening guide for WAF : we use F5.

Can anyone point me to such a hardening guide for F5 WAF?

if there's none, any link/authoritative guide indicating it's been
sufficiently hardened (as it's an appliance customized from RHEL 5?)
will be appreciated.

Need a good justification why we don't have hardening guide in place
for F5 WAF
How do i register SUSE Linux to customer portal?

also how to check what security packages are available to install?

I have worked on RHEL and we use subscription manager to register with customer portal or redhat satellite.

what is the procedure for suse linux? what tool similar to redhat satellite SuSE uses?

When i search on below command
ps -ef|grep zyz3abc
i see all the proceses running for zyz3abc
how to seach using particular port number(1567) to filter down more granular

 i tried

ps -ef|grep zyz3abc grep 1567
did not see to work.
please advise

shared book marks in winscp name can i give custom names like Integration Log path, Production1 Log path etc. can you please advise

if path says crm/net/logs etc on Production1, Production2, Production 3 boxes then i cannot clearly distinguish and add as separate names. please advise

how to copy test folder files
from below
to below folder

trying cp command but not working
is -r different from -R

please advise
do i need to go to /crm/home/XYZ3ABC/config/security/test to execute cp command or  to  /crm/home/systemtest/security/test

Lets say i want to copy bunch of files from




How to this copy paste.
can i do using winscp whose interface easy to me and more convenient to work than unix screens which according to me most non user friendly

Also once i copy files i need to edit those bunch of files from xyz3abc to xyz3abc2 etc
any way i can edit files without using vi which i am not 100% comfortable.
can i use winscp to edit or any other good open source tools apart from winscp

please advise
I have the following RPM installed on my server.  based on the security report, its RHSA-2016:0005 missing.


according to RHSA-2016:0005 , i need to install

Red Hat Enterprise Linux Server (v. 6 for 64-bit x86_64)

This is my running kernel. RHEL 6 x86_64.

is it true vulnerability ? or is it false positive? please explain.
Hi,what is difference between 755 and 777 privileges to a directory or a file in unix world.
please advise

Linux Security

The Linux operating system, in all its flavors, has its own share of security flaws that allow intrusions, but there are various mechanisms by which these flaws can be removed, generally divided into two parts: authentication and access control. Authentication is responsible for ensuring that a user requesting access to the system is really the user with the account, while access control is responsible for controlling which resources each account has access to and what kind of access is permitted.