Linux OS Dev

Kernel programming for Linux operating systems can be done with many different languages; C, C++, Python, Perl and Java, which are some of the most common languages used.There are also many different varieties of Linux, such as Ubuntu, Fedora and OpenSUSE.

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1. Can someone explain me if there is any changes in .cloginrc file, I need to run the rancid-cvs and rancid-run,
2. When i am trying to login i can see that the username is not pulling from what is there in .cloginrc.

For Eg:
(Under my clogin file)
I have mentioned
add user 1x.x.x User1
add password 1x.x.x       {password}
add method 1x.x.x telnet ssh

But when i am trying to login, i can see that username is in rancid. I am not sure why its happening. And to make sure that if try firewall login or normal login, its going with actual username only
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on my windows 10 machine after installing oracle virtua box and centos on top of it while starting getting below error

Failed to open a session for the virtual machine centos.

The virtual machine 'centos' has terminated unexpectedly during startup with exit code 1 (0x1).  More details may be available in 'C:\Users\saiganesh\VirtualBox VMs\centos\Logs\VBoxHardening.log'.

Result Code: E_FAIL (0x80004005)
Component: MachineWrap
Interface: IMachine {b2547866-a0a1-4391-8b86-6952d82efaa0}

i tried on other laptop i do not see red hat 64 some reason but shows red hat 32 bit

Please advise
how to remember shell history and how to save unix queries for future use and share with the team

$HISTSIZE can be increased to unlimited size?

how to type attached l character

please advise
how below commands are different

su department (when i do pwd here says department)
su - department(when i do pwd here says /home/department)

when i do below

su -c 'echo $echo  $DEPARTMENT_HOME' department
it does not work

when i do below

su -c 'echo $echo  $DEPARTMENT_HOME'  - department
it does work. Please advise the difference.

what is difference between
department and  /home/department

how su and sudo are different?

how can there is depearment inside home as well as outside at top level again?

what is visudo and sudoers file or folder?

Please advise
difference between below process killing signals

kill -15 123


kill -TERM 123

kill -9 123

how foreground and background processes are different and how to kill or suspend them?
is PID is always 4 digit or it can be 10 digit etc?

how job and process different?
how to distinguish between background and foreground jobs?

when i say

it simply shows 5 different jobs one with + other with -

but does not show whether background or foreground?

i have a job running in background i brought it to foreground and stopped it.
when i moved it again to background it automatically moved to RUNNING status? how this is possible?
how terminated suspended and killed etc are different?
Please advise
How to view the contents of a VMCORE file?
Similar to what Author Comment by:apunkabollywood did on ticket ID: 39512494 2013-09-21
Individual log  files on my server getting zipped every 1 hour and individual log files getting deleted.

PRoblems i am facing with zipped log files are
1. not able to grep them as easily as individual files

2. not able to tail to see any recent issues

if i copy over to local windows laptop using winscp and unzil anf try to open individual file using notepadd++ says too huge file to open.

how to extract zip file in unix box itself and check log files by doing grep and tail etc

please advise
Hi Experts

Could you clear what must to be done before to install Lubuntu 64 bits ?

After download Lubuntu installer at  Lubuntu  and obtain what I expect to be the installer:

And when trying to install it a DVD burn software starts...

So, is it obligatory to create a DVD instalator before to install it?

But, if I want to start from a pen-drive f.e. , do I have any workaraound?

Thanks in advance.
Hi Experts

Could you point the more convenient  Ubuntu version and  where to obtain it to fit  with this hardware?
(an old laptop)

Thanks in advance!
I have a Samsung Galaxy S9+.
Android Version: 8.0.0

I recently put a micro SD card in it and moved many apps to it.  One of them was Bejeweled Classic by Electronic Arts.  Later I noticed that the icon for it was missing, so I went to download/install it again.  When that happened I got a strange error message: "You cannot install this app because another user has already installed an incompatible version on this device"

NOTE: I cannot find the app on my Installed Applications list.

You cannot install this app because another user has already installed an incompatible version on this device
In the link above someone wrote:
What worked for me was: adb shell pm uninstall com.packagename

I have a Terminal Emulator to try that command, I just need to know the exact packagename.

Question: How do I get a listing of package names in the Terminal Emulator?

Screenshot of error message
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We have setup OpenVas in our infrastructure. We were able to run it in order to scan assessments reports on VM's within our infrastructure. However the results of the scans is very long and complete. We would like to filter that same report in order to only have results of the High severity reports.

Any idea on what would be the most effective approach to filter the Greenbone scans?

after i installed nextcloud 13.0.1 on centos 7 and most of the features works

i am facing a strange issue with calendar

i cannot create or delete or do anything with calendar on nextcloud management    please check the attached file

do you think i have to change something from GUI or CLI  or install or do something

kindly advice
How to send a command /dev/ttyXX.

I've tried these and none seem to worK;
1. echo "stop" > ttyS1
2. echo -ne "stop\n" > ttyS1
securecrt vs putty

what additional feature or advantages or disadvantages securecrt has compared to putty or mputty.

how much is the licence cost per year or life time?

any advantages using securecrt or any other commercial better tools?

please advise
winscp how to grep or search on a word say "xyz" in all the folders and sub folders
Please advise
Hello Experts,

Getting following error while execute cmd from ssh :-

[root@200 ~]# separateBod
Option "-t" is deprecated and might be removed in a later version of gnome-terminal.
Option "-t" is deprecated and might be removed in a later version of gnome-terminal.
Failed to parse arguments: Cannot open display:

separateBod Code:-
 read IPNAME
 for i in $IPNAME
  ssh user@192.168.1.$i BOD & pid=$!

BOD Code:-
gnome-terminal \
        --tab -t "Exchange" -e " sh -c 'sleep 1s; ./startapp Exchange' "\
        --tab -t "Dragon" -e " sh -c 'sleep 10s; ./startapp Dragon' "\

startapp code:-
ulimit -c unlimited
./$1 $2 $3 $4 $5

After giving execution cmd from server (ssh) it should be displayed on other server vnc (user@, it was working properly till last week suddenly i got this error, we have following versions of CentOS 64bit (6.7, 6.8, 6.9, 7.4), getting issue only with 7.4 64bit.

please suggest.
winscp how to name the link i save to favorite

say i have link

i want to save above link with name as production_logs_folder

I have other link as below


i want to save above link with name as crm_logs_folder

how do i name like above so that it is easy to locate and navigate later
\please advise
I have had to disable SELinux to get an application installed ,I was wondering if anyone has ever used 'AUDIT2ALLOW' to re-tag the objects in SELINUX and re-enable SELINUX  

I have never ever worked with SELINUX before and could use any advice you can give
log file how to copy whole content

zgrep -C20 '1234' 1234.log.gz

above gave lot of results in unix screen

how to copy whole page and paste into a text file on my C drive of the windows laptop through which i am connecting to unix box using putty?


i see all results like



which i do not want

i want complete word search of 1234 only
how to achieve it
please advise
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what is curl and ping in unix.

lets say i have service called

now if do
get the exact_name of service from above result
then use that exact name to ping
ping exact_name
then we can get ip of the service where it is running?

please advise
how can I suppress this message when ssh into a linux server , i cant seem to find this like no check or something ,

ECDSA key fingerprint is MD5:de:66:6wea:32:dw2:65:d7wwwwwww:1c:a4:05:e0.
Are you sure you want to continue connecting (yes/no)? yes
I can see all processes in my box using memory total as 25GB but the actual memory used is 62GB, I am really confused that what happened for remaining memory....don't know whether i need to clear memory cache or not?

test@test[~] $  ps aux  | awk '{print $6/1024/1024 " GB\t\t" $11}'  | sort -nr | awk '{print $1}' | awk '{total = total + $1}END{print total " GB"}'
24.4622 GB
test@test[~] $ free -g
                            total       used       free     shared    buffers     cached
Mem:                      62         62          0          0               2             32
-/+ buffers/cache:              27         35
Swap:                        7          0          7
test@test[~] $

Open in new window

memory issue
What awstat format i need for that type af log from ftp server
Feb 26 13:47:24 ftp sshd[1260]: Disconnected from port 36575 [preauth]
Feb 26 13:47:24 ftp sshd[1260]: PAM 2 more authentication failures; logname= uid=0 euid=0 tty=ssh ruser= rhost=  user=root

i used all 1 ...4 then i used :
LogFormat= "%time3 %other %method %url %logname %host %code %other"
LogFormat= "%time3 %other %host %bytesd %url %other %other %method %other %logname %other %code %other %other"

all says  
found 401 dropped records
2000 corrupted records
how can i send out put from own scripts to nagios 4.3.4
i have a scrip to count som special open files. in this. in this open file 10 of them are contain localhost in path of open files
den command like check_nrpe -H localhost(or ip number) -c check_own_scripts
count only all files which is contain localhost in path itmeans return 10
but when run ./check_own_sripts returns 800.
what i did wrong here. it's just simple scripts
lsof -p pid | wc -l
I am unable to roll back my recent updates.

[root@ansible ~]# yum history
Loaded plugins: product-id, search-disabled-repos, subscription-manager
ID     | Login user               | Date and time    | Action(s)      | Altered
     7 | root <root>              | 2018-02-28 13:11 | Erase          |    2
     6 | root <root>              | 2018-02-27 18:12 | I, O, U        |  309 EE
     5 | root <root>              | 2017-11-18 12:57 | I, U           |   32
     4 | root <root>              | 2017-11-16 01:13 | Install        |   33
     3 | root <root>              | 2017-11-16 01:10 | Install        |   23
     2 | root <root>              | 2017-11-05 10:37 | Install        |   13 E<
     1 | System <unset>           | 2017-11-05 10:01 | Install        |  385 >
history list

[root@ansible ~]# yum history undo 6
Loaded plugins: product-id, search-disabled-repos, subscription-manager

..........(output omitted)
---> Package zlib.i686 0:1.2.7-17.el7 will be erased
--> Processing Conflict: kernel-3.10.0-693.17.1.el7.x86_64 conflicts kexec-tools < 2.0.14-3
--> Finished Dependency Resolution
Error: kernel conflicts with kexec-tools-2.0.7-50.el7.x86_64
 You could try using --skip-broken to work around the problem
 You could try running: rpm -Va --nofiles --nodigest

Linux OS Dev

Kernel programming for Linux operating systems can be done with many different languages; C, C++, Python, Perl and Java, which are some of the most common languages used.There are also many different varieties of Linux, such as Ubuntu, Fedora and OpenSUSE.

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Linux OS Dev