Category: RHCSA

Red Hat Certified System Administration

Dec 31

Experiment with Selinux

Target Audience:  Technical People (who already knew or did similar stuff, at least worked well with Linux ) If you find these impossible to understand on your own (however, want to understand), better take help from Technical People Selinux provides further security in addition to chmod, chown, facl, setuid, setgid or similar. Firewall controls incoming …

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Dec 26

AutoFS and Mounting in Linux/Redhat/CentOS

AutoFS and Mounting in Linux/Redhat/CentOS echo “AutoFS – Automatic FS system Mounting – Dec 26th, 2017 by Sayed” check if Autofs installed or not yum list installed | grep autofs I just installed; hence it is there you can install with yum -y install autofs 944 yum -y install autofs then you can enable autofs …

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Dec 26

On File Systems and Linux Commands (Redhat/CentOs/Fedora)

On File Systems and Linux Commands (Redhat/CentOs/Fedora) echo “Dec 26th, 2017, Sayed Ahmed, Justetc Technologies” On file Systems – Target Audience: Technical People. Software Developers and System/Network Administrators or DevOps  (or wanna be) / and /boot are the default Linux file systems you can also configure /home, /opt, /var, /tmp, /usr as separate file systems …

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Dec 25

Users and Groups management in Linux (Redhat/CentOS/Fedora)

Users and Groups management in Linux (Redhat/CentOS/Fedora) Target Audience: Technical people who knew or already know (to some extent) – just wanna review Yes, from my history 622 echo “dec 25th, 2017 – sayed”   User and password related files 623 cat /etc/passwd 624 cat /etc/shadow 625 cat /etc/group 626 cat /etc/gshadow There are some …

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Dec 24

NTP related commands/Linux

598 echo “dec 24th, 2017” 599 echo “NTP Client” 600 yum list ntp 601 yum list installed |grep ntp 602 To activate ntp 603 yum -y install ntp system-config-date 604 cat /etc/ntp.conf 605 grep ^server /etc/ntp.conf 606 systemctl restart ntpd 607 systemctl enable ntpd 608 systemctl start ntpd 609 ntpq -p 612 nmtui 613 ip …

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Dec 24

Network Interface, Network Clients related Linux/Redhat/CentOS commands

echo “Dec 24th, 2017” 532 echo “Basic Networking in Linux” 533 hostname 534 uname -a 535 uname -n 536 cat /etc/hostname 537 nmcli general hostname 538 changing hostname temporarily 539 hostname server10.example.com 540 for permanent change 541 hostnamectl set-hostname server100.example.com 542 or change /etc/hostname file 543 vim /etc/hostname 544 restart systemctl 545 systemctl restart systemd-hostnamed …

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Dec 24

TCP Wrappers in Linux/CentOS/Redhat/Fedora

yum info tcp_wrappers yum install tcp_wrappers-devel.x86_64 506 reboot 507 ifdown ens33 508 ifup ens33 509 yum install tcp_wrappers-devel.x86_64 510 yum -y install tcp_wrappers-devel.x86_64 511 ls /var/ftp/pub/Packages/ 512 ls /etc/yum.repos.d/local.repo 513 vim /etc/yum.repos.d/local.repo 514 systemctl status vsftpd 515 systemctl start vsftpd 516 systemctl enable vsftpd 517 yum -y install tcp_wrappers-devel.x86_64 518 cat /etc/hosts.allow 519 cat /etc/hosts.deny …

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Dec 24

SSH/SSHD/OpenSSH in CentOS/Redhat Linux

Experiment with SSH/SSHD/OpenSSH in CentOS/Redhat Linux Yes, from  my history (Probably a review for the technical people, who already knew these sometimes in the past) 461 echo “dec 24th, 2017” 462 vim /etc/ssh/sshd_config 463 echo “SSH Related Commands” 464 scp -> secure copy 465 tscp -> secure copy for windows 466 sftp -> secure ftp …

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Dec 22

Disk/Partition/Logical Volume (LVM) Management related commands in Centos/Redhat Linux

echo “Dec 22nd 2017” 321 pvs 322 output 323 PV VG Fmt Attr PSize PFree 324 /dev/sda2 cl lvm2 a– 19.00g 0 325 pvs 326 vgs 327 lsblk 328 vgdisplay 329 vgdisplay | grep “PE Size” 330 PE Size 4.00 MiB 331 vgdisplay > vgdisplay20171222.txt 332 vgdisplay | grep ‘PE Size’> vgdisplay20171222.txt 333 lvs 334 …

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Dec 21

Redhat/CentOS Linux and Disk/Volume Management. LVM, parted, gdisk, vgcreate, lvcreate and similar

Misc related commands from history [Redhat/CentOS Linux and Disk/Volume Management. LVM, parted, gdisk, vgcreate, lvcreate and similar]   fdisk /dev/sdb 93 parted 94 parted /dev/sdb 96 parted /dev/sdb print 97 vi /etc/fstab 98 parted /dev/sdb 99 vi /etc/fstab 100 parted /dev/sdb 101 parted /dev/sdb print 102 gdisk /dev/sdc 103 gdisk -l /dev/sdc 104 fdisk -l …

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Dec 18

Step by Step: How to Install and Configure LDAP Server

From my history of executed commands. The command sequence works like charm [though some commands might fail as I am directly pasting from history] You can check our other posts on LDAP client configuration. Also, go to the end of the commands list; some config file contents will be provided. These files need to be …

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Dec 15

Experiment with Firewalls in Linux (CentOS/RedHat)

44 firewall-cmd –state 45 systemctl status firewalld 46 firewall-cmd –reload 47 systemctl restart firewalld.service systemctl restart firewalld 48 firewall-cmd –get-default-zone 49 firewall-cmd –get-active-zones 50 firewall-cmd –get-zones 51 firewall-cmd –get-zone-of-interface=ens33 52 firewall-cmd –list-all 53 firewall-cmd –list-all-zones 54 firewall-cmd –get-default-zone 55 firewall-cmd –get-active-zones 56 firewall-cmd –list-all 57 firewall-cmd –get-zones 58 firewall-cmd –list-all-zones 59 firewall-cmd –list-all –zone external …

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Dec 12

Linux: LVM : Logical Volume Manager : Multiple Hard Disk and Partition and Volume Management

On RedHat/Centos Linux – LVM experiments Concepts to understand: Physical Volume: Physical Hard Drive or  Partitions in Physical Hard Drive Physical Extent:  One unit of space usually 4 MB. Volume Group: One or multiple Physical Volumes can be assigned to a Volume Group Logical Volume: Logical volumes are created from the volume groups. This is …

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Dec 08

Configure Virtual Machine using CentOs/Redhat Virtualization Features

Yes, taken from the output of the history command Check for Virtualization Support lscpu | grep Virtualization grep vmx /proc/meminfo  (should be in Redhat/CentOS installed in the actual machine – not when Linux is under VM)   Check info on different related packages yum group info “virtualization hypervisor” vim /etc/yum.repos.d/CentOS-Base.repo yum install tree ping yahoo.com …

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Dec 08

Experiment with Misc. Linux (Redhat/CentOs) Commands: Permission, kill, ps, virtualization, firwall, star, environment variables, fsck

Yes, taken from the output of the history command ll chmod 755 /var w whoami who id   With Star star cvf /tmp/etc.tar -xattr -H=exustar /etc cd /tmp ls -la etc.tar star tvf etc.tar star tvf etc.tar star xvf etc.tar Attributes lsattr etc.tar chattr +a etc.tar lsattr etc.tar   Permission Related umask umask -S touch …

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Dec 08

Redhat/CentOS, Selinux: Linux Security: and related

From my history (i.e. taken from output of history command) Check if internet connection is there otherwise yum might not work as yum goes to the internet to find packages (unless you are using local yum servers) ping yahoo.com nslookup yum install selinux : will not work as it is you can try yum install selinux*, …

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Dec 08

Misc Linux (Redhat/CentOS) Commands. User Group Password star wc w who id group

Create user and assign to a group useradd joseph usermod jerry -G wheels usermod –help   Check users and Groups listed in related files cat /etc/passwd cat /etc/group Try to install star – standard tar (supports extended attributes for Selinux as well) yum install star star yum is not there. so use rpm to install …

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Dec 07

On Creating a Yum Server on Redhat/CentOS Linux

Mount Installer ISO mkdir /mnt/dvd1 mount /dev/sr0 /mnt/dvd1 Check if FTP server is installed systemctl status vsftpd systemctl start vsftpd Install ftp Server. Using rpm as yum is not available yet [default yum needs the internet, kindof] cd /mnt/dvd1/Packages/ rpm -ivh vsftpd-3.0.2-22.el7.x86_64.rpm systemctl start vsftpd systemctl enable vsftpd Copy rpm installer packages to the FTP …

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Dec 04

Create your own yum repo in Centos/Redhat

Yum is a software installation manager for Redhat Linux and Related. yum is a better tool than rpm. Here, we will take the rpm packages as come with Redhat/Centos and then we will host those packages on our own Repo Server for yum. i.e. yum will use this Repo to find installers rather than going …

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Dec 04

Miscellaneous CentOS/RedHat/Fedora Commands. Yum Repo, Firewall, User Permissions, Virtualization Manager

Misc Linux Commands from .bash_history file Add a user and assign to a group useradd joseph usermod jerry -G wheels usermod jerry -G wheel usermod –help   Check the created user in the file where some user info are kept cat /etc/passwd cat /etc/groups cat /etc/group exit   Try to install star: Standard tar yum …

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Nov 30

Selinux and Security in Linux

Find out the Selinux packages available rpm -qa | grep selinux The output: libselinux-utils-2.2.2-6.el7.x86_64 libselinux-2.2.2-6.el7.x86_64 selinux-policy-targeted-3.12.1-153.el7.noarch selinux-policy-3.12.1-153.el7.noarch libselinux-python-2.2.2-6.el7.x86_64 Install Selinux yum install policycoreutils policycoreutils-python selinux-policy selinux-policy-targeted libselinux-utils setroubleshoot-server setools setools-console mcstrans     SELinux Modes Enforcing Permissive Disabled   Check Modes: getenforce sestatus (some more details) Related Files: cat /etc/selinux/config cat /var/log/messages | grep “SELinux is preventing” …

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Nov 22

Linux vs Unix

Posix: “a set of formal descriptions that provide a standard for the design of operating systems, especially ones that are compatible with Unix.”. Considering POSIX, Linux can be thought as Unix. Though Unix is copyrighted. Topic Unix Linux Is Complete Operating System? Yes,  everything comes from a single vendor Linux is kinda Kernel only then …

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Nov 22

Recursive chmod Tricks

Right now, I just had to use some of the following commands… I used the Quickinstall to install some software though I saw the .php files do not have execute permissions on them. The idea is find the files or directories that you want to change and then apply the exec chmod find command is …

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Aug 13

Issues and solutions for moving WordPress based applications from one hosting to another

Just moving the Training and Education site http://SitesTree.com to a different hosting i.e. from a reseller hosting to a Cloud Hosting (no, it is not AWS or Azure or Bluemix cloud, just the as usual cloud hosting provided by some regular hosting provider. ) . Just two cents on how this moving (WordPress) can be done.

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Jan 02

A Hands on Guide

A Hands on Guide: A Hands on Guide

Jan 02

Fedora Linux Essentials

Fedora Linux Essentials: Fedora Linux Essentials

Jan 02

Debian GNU/Linux Desktop Survival Guide

Debian GNU/Linux Desktop Survival Guide: Debian GNU/Linux Desktop Survival Guide

Jan 02

Building Applications with the Linux Standard Base

Building Applications with the Linux Standard Base: Building Applications with the Linux Standard Base

Jan 02

Beyond Linux from Scratch

Beyond Linux from Scratch: Beyond Linux from Scratch

Jan 02

Linux Device Drivers, 2nd Edition

Linux Device Drivers, 2nd Edition: Linux Device Drivers, 2nd Edition

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