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Linux is a UNIX-like open source operating system with hundreds of distinct distributions, including: Fedora, openSUSE, Ubuntu, Debian, Slackware, Gentoo, CentOS, and Arch Linux. Linux is generally associated with web and database servers, but has become popular in many niche industries and applications.

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how can I have an instace of CENTOS in AWS and be able to login with one user that has a key and other user that will be only able to login with user name and password

is this possible?

Visualize your virtual and backup environments
Visualize your virtual and backup environments

Create well-organized and polished visualizations of your virtual and backup environments when planning VMware vSphere, Microsoft Hyper-V or Veeam deployments. It helps you to gain better visibility and valuable business insights.

I would like to be able to run commands from a windows machine (using some tool ) and run commands in linux machine and retrieve results of those commands.
I have a powershell code which connects to remote windows systems, I want to be able to retrieve system info from linux machines as well. Is this possible?

This is in relation to this question:
 powershell to linux.
Dear Experts,

I'm using zabbix to monitor my local devices, server,..., and I want use EnableRemoteCommand feature in zabbix to start/stop, restart services when it crash or die.
I've configured trigger & action in zabbix . I've also configured sudoers on zabbix-agent machines. But when I test run command: sudo -u zabbix /usr/bin/systemctl restart httpd.  with user zabbix, it require root's password.

Here is my sudoers config:
zabbix ALL=NOPASSWD: /usr/bin/systemctl restart httpd
%zabbix ALL=(ALL) NOPASSWD: /usr/bin/systemctl restart httpd

How about set root privileges for user zabbix ?, but I think it's not recommend. So please help me to config allow zabbix user can start/stop services on centos 7.

I had this question after viewing (Open)LDAP V2.44  search proxy to AD (W2012R2).

I am following this article ( in order to set up an OpenLDAP proxy.  But when I run an ldapsearch command on the Windows AD, I get the bind error below:

root@VMUSDevLDA01:/etc/ldap# ldapsearch -x -h  "(objectclass=*)"
# extended LDIF
# LDAPv3
# base <> (default) with scope subtree
# filter: (objectclass=*)
# requesting: ALL

# search result
search: 2
result: 1 Operations error
text: 000004DC: LdapErr: DSID-0C090752, comment: In order to perform this opera
 tion a successful bind must be completed on the connection., data 0, v2580

Here is my nslcd.conf file, what is wrong with it?

# Mappings for Active Directory
pagesize 1000
referrals off

# Passwd
filter passwd (&(objectClass=posixAccount)(!(objectClass=computer))(uidNumber=*))
map    passwd homeDirectory     UnixHomeDirectory
map    passwd gecos             displayName
map    passwd gidNumber         primaryGroupID

# Shadow
filter shadow (&(objectClass=posixAccount)(!(objectClass=computer))(uidNumber=*))
map    shadow shadowLastChange  pwdLastSet

# Groups
##filter group (&(objectClass=posixGroup)(gidNumber=*))
##map    group uniqueMember       member

# Local account for nsclcd
uid nslcd
##gid ldap
I am attempting to find a place to pay for advertising for technical  courses we are giving , it has to do with Linux in general . Where do you think a good place it to PAY for an ad for this kind of training ??/

in .bashrc there is an area where you add aliases.  It had been set up so you could store all your aliases in an external file ".bashrc_aliases".  There was something like (i forget the exact syntax):
if -f ".bashrc_aliases"
I erased the text between if and fi and I put the .bashrc_aliases file into .bashrc trying to find an error.  I found the typo and now I want to move the aliases from .bashrc back to the file ".bashrc_aliases".  I forget what I erased between if and fi to include the file ".bashrc_aliases".
Begin Process info for 21444
Mon Jun 19 13:30:21 UTC 2017
Thread 224 (Thread 0x7f2fe55f1700 (LWP 21454)):
#0  0x000000325fc0b68c in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/
#1  0x00007f2ff296e98e in NQConditionWait::Wait() () from /u01/app/obiee12c/bi/bifoundation/server/bin/
#2  0x00007f2ff29bbfe8 in NQSemaphore::Acquire() () from /u01/app/obiee12c/bi/bifoundation/server/bin/
#3  0x00007f2ff2970389 in NQConditionWaitLIFO::Wait(NQSemaphore&, PerfTimeSnap&) () from /u01/app/obiee12c/bi/bifoundation/server/bin/
#4  0x00007f2ff29704b9 in NQConditionWaitLIFO::Wait() () from /u01/app/obiee12c/bi/bifoundation/server/bin/
#5  0x00007f2ff29d7802 in PoolThread::ExecuteUserMain() () from /u01/app/obiee12c/bi/bifoundation/server/bin/
#6  0x00007f2ff2998f39 in NQExecutionState::ExecuteSystemMain() () from /u01/app/obiee12c/bi/bifoundation/server/bin/
#7  0x00007f2ff29d3f06 in NQThread::ExecuteSystemMain() () from /u01/app/obiee12c/bi/bifoundation/server/bin/
#8  0x00007f2ff29d44ae in NQThread::ThreadMainEntry(void*) () from /u01/app/obiee12c/bi/bifoundation/server/bin/
#9  0x000000325fc07aa1 in start_thread () from /lib64/
#10 0x000000325f4e8bbd in clone () from /lib64/
Thread 223 (Thread 0x7f2fe54f0700 (LWP 21455)):
#0  0x000000325fc0ba5e …
I have a box that I configured to use MD RAID during the install process for the OS and boot drive. It's this weird /dev/md0p# structure that confuses me.

The installer produced /dev/md0p1 (/boot), /dev/md0p2 (/var/lib/mysql), /dev/md0p3 (/), /dev/md0p4 (extended), /dev/md0p5 (swap). I noticed it did this for all physically installed machines from the CentOS 6 DVD.

How do I increase the size of the /dev/md0p3? I need this root partition to be expanded. I feel like I need to delete the /dev/md0p3, /dev/md0p4, /dev/md0p5 partitions and then create a new one for /dev/md0p3 with the extra space. I don't care for p4 and p5, because they don't contain actual data. I can create them after the fact.

I am confused on the order of deleting partitions and adding the space in respect to /dev/md0. fdisk -l shows the drives /dev/sda, /dev/sdb and then finally /dev/md0 with all of the sub partitions.
Hi ,
I have deployed new nagios server centos 7.3 add host (centos 7) using nrpe but getiing this error " No output on stdout) stderr: connect to address port 5666: No route to host  "
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I have linux server and i want to count pdf pages is colored or bw.

i have used imagemagic but it takes serverd down so can you help me with alternative way?
Hello All,

I am in a situation to push database audit XML logs to syslog server. Audit logs are getting generated when Audit_Trail is set to OS. The same is not happening when Audit_Trail is set to XML,EXTENDED. Please advice on this.

SQL> select banner from v$version;

Oracle Database 10g Enterprise Edition Release - Prod
PL/SQL Release - Production
CORE      Production
TNS for Linux: Version - Production
NLSRTL Version - Production

SQL> show parameter audit
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
audit_file_dest                      string      /u01/appldrch/DRCH_DB_audit_lo
audit_sys_operations                 boolean     TRUE
audit_syslog_level                   string      LOCAL1
audit_trail                          string      XML, EXTENDED

[root@appsdr ~]# cat /etc/syslog.conf
local1.warning /var/log/audit.log

Thank You.

John Marshal.A
Hi friends,

I'm in (preemptive !) need for some bootable antivirus rescue disk for offline scanning of Linux systems - preferably a flavour that could be banned onto a bootable USB stick and with good test results ...

Any recommendations ?
I am trying to clone this VM to another host and noticed it has 450GB allocated as "Thick Provisioned Lazy Zeroed"
On the OS level though I see only 188GB of this is actually used.
 I would like to reduce the disk size to say 300GB and then clone it but am not sure how to do this.
I think I need to use vMotion somehow but first wouldn't I need to make sure the data in the OS level is not located at the end of the disk?
Hi Experts,

I want to connect to multiple redhat machines from Windows powershell and retrieve configuration info from redhat systems.

What is the best way to achieve this. ?

I know there is a putty tool to connect to linux systems but is there a way to retrieve info from redhat machines like CPU, memory etc.

I would really appreciate if you could help..

I am a beginner with this, and after configuring JAVA and Wildfly, I get the following error when trying to run :

14:27:33,895 ERROR [] (Controller Boot Thread) WFLYSRV0055: Caught exception during boot: WFLYCTL0085: Failed to parse configuration
        at [wildfly-controller-2.2.0.Final.jar:2.2.0.Final]
        at [wildfly-server-2.2.0.Final.jar:2.2.0.Final]
        at$ [wildfly-controller-2.2.0.Final.jar:2.2.0.Final]
        at [rt.jar:1.8.0_131]
Caused by: com.ctc.wstx.exc.WstxParsingException: Received non-all-whitespace CHARACTERS or CDATA event in nextTag().
 at [row,col {unknown-source}]: [87,9]
        at [woodstox-core-asl-4.4.1.jar:4.4.1]
        at [woodstox-core-asl-4.4.1.jar:4.4.1]
        at [woodstox-core-asl-4.4.1.jar:4.4.1]
        at …
Hi, some time ago I have cloned and installed this project on the VMs where SELinux was disabled
And now I can see this doc , where they say: Security-Enhanced Linux (SELinux) must be enabled on all of the servers before installing OpenShift Origin or the installer will fail.
So my question is how does Openshift play with SELinux? What is the algorithm of this play?
This is using Amazon t2-micro AMI 64-bit linux EC2 instance. I have a gmail email address, thinking of setting up a mail client, with correct credentials so as email can be sending out from this server. I saw a Sendmail daemon is running. I am thinking of sending a tripwire report to my gmail email address, with the cron job command as shown:

/usr/sbin/tripwire -m c | mail -s "Tripwire Report from HOST"

I heard that sendmail client is pretty difficult to setup. How about other mail client, such as postfix, and so on.

Thanks in advance.
Hi All,

After the filesystem issue on my VCSA v6.5, I suddenly unable to login to the server with the below error:

A server error occurred.
Unable to log in because you do not have permission on any vCenter Server systems connected to this client.
Check the vSphere Client server logs for details.

Open in new window

I can login using administrator@vsphere.local but not anything with AD integrated account.

Here's the chronological order:

-- vCenter server down
-- not pingable.
-- Issues seen in the ESXi host which the vCenter VM is residing on :

2017-06-17T11:07:34.592Z: [scsiCorrelator] 2630366567703us: [] Lost connectivity to storage device naa.6000eb3311ab55e3000000000000040f. Path vmhba37:C0:T9:L0 is down. Affected datastores: "PRODSQL01_Backup"..

-- vCenter VM hangs in the black screen - where it goes into the single user mode.

Reason :
-- The root filesystem has mismatching inodes.

Action taken :
To fix the issue we went ahead and cleaned the filesystem bad blocks.

executed the below commands :
1. Check the filesystems :


2. Run the e2fsck against the filesystem for root

e2fsck /dev/sda3

3. Fix the inodes when asked for it
4. Once process completes, reboot the virtual machine.
Stressed Out?
Stressed Out?

Watch some penguins on the livecam!

This is using an Amazon ami 64-bit EC2 instance. This is an web application server that do some routine registration. I am thinking of gathering and backing up some of the log files for further auditing purposes. please see the list of log files:


    Monitor default audit rules/custom audit rules


    Not entirely sure if I would be able to glean any intrusions/modification from this but this would give me an idea of the system state on start-up

/var/log/secure & /var/log/wtmp

    Authentication attempts/fails

"/var/log/httpd/ssl_error_log*" & "/var/log/httpd/ssl_access_log*"

    Access and error log for webpage (not sure if this would help holding onto these...but it could give an insight if a random IP kept hitting my webpage. Wouldn't prove anything but might warn?)

I am thinking of compress and backing up as an additional copy, let's say once every week. btw, please shed a light on how can I achieve this probably with the use of cron job?

Thanks in advance.
I restored a backup of my website and uploaded filers to my website folder /home/mywebsite/public_html using Bitvise FTP

The permissions for Owner ID & Group ID come up as 0 & 0, is there a Linux command to set Owner ID 515 & Group ID 526
What is a quick but definite test to run from the Linux command line to check if dns requests are being hijacked. The test should not require having to change the dns servers for the device that the test is being run from.
This is an attempt to setup clamav on the Amazon t2-micro 64-bit linux server, with 1 gb ram. Initially, the packages were downloaded as follows:

sudo yum install clamav clamav-scanner-sysvinit clamav-update –y

After that, the freshclam.conf was updated as follows:

sudo vi /etc/freshclam.conf

Remark of:

Remove the remarks of:
DatabaseDirectory /var/lib/clamav
UpdateLogFile /var/log/freshclam.log
DatabaseOwner clamupdate

Run the freshclam, and got all the main updates downloaded

Then, update the scan.conf

sudo vi /etc/clamd.d/scan.conf:

Remark of:

Remove the remarks of:
LocalSocket /var/run/clamd.scan/clamd.sock
FixStaleSocket yes
TCPSocket 3310

But this time round, attempt to start the clamd.scan daemon failed. Please see the errors on /var/log/messages as attached.

Look like the RAM is not enough? I heard that we can change to use cron job to replace the daemon, for this low memory system, is that true? or else any resolution?
I had this question after viewing Network issues with Linux Bonding and Cisco 2960-S.

Old, question... but its talking about bonding cisco and linux sides.  I have successfully setup linux bonding (mode 4 - lacp ) with cisco switches ( 4948 ) in the past.  But what i want to do now, i dont know enough about cisco to do so.  I am a devop guy, so networking, especially cisco gear, is a little outside by knowledge base.  

setup some kind of bonding on the cisco side that allows me to first plug a server in, boot it, install from the network, then reconfigure it into a bonding setup.... automatically.

I have a bunch of servers i am trying to automatically deploy.  i want to boot them up with nothing on them, use the ubuntu MAAS (metal as a service ) to install an OS on them, then use ansible to connect to the newly installed server to then create the interface bonds.  At that point, i would then like the cisco switch to use lacp( or some type of similarly useful bonding ).  

The issue is a chicken/egg scenario.  You have to create the port channels on the cisco and add the ports to them and set them for lacp( as far as i know, and why i am asking this ).  On the linux side, you then need to setup bonding and set the mode to 4.  Since i am doing everything automagically using MAAS and ansible ( tested and working ).  It SEEMS i cannot setup the …
I have a PowerEdge 2950 running Red Hat 6 - 64 that hosts a D3 Tigerlogic Multivalue Database. Been trying to P2V to create a VM for testing config changes. I've read dozens of online responses about the "No Operating System" error on the VM, but Linux is foreign to me and this server has a very complex history. Appears to have HARDWARE and SOFTWARE RAID and several mount points and Samba shares. I've tried the Red Hat DVD rescue fixes, but no go. Just don't understand what the bios is looking for on which partition to get it to boot. I believe all the partitions exist and are complete. Would really like an exact VM replica of the server. Going to try clonezilla booted off DVD next.





Articles & Videos



Linux is a UNIX-like open source operating system with hundreds of distinct distributions, including: Fedora, openSUSE, Ubuntu, Debian, Slackware, Gentoo, CentOS, and Arch Linux. Linux is generally associated with web and database servers, but has become popular in many niche industries and applications.