RHCSA Red Hat enterprise Linux 7 (RHEL 7) preperation (March 2015) (EX200)

rhel redhat test

Chapter 1. Installation with local DVD

Note: not required in exam

1. History

Richard Stallman: GNU(GNU's Not Unix project), 1991
Linus Torvalds: kernel, 1991

RHL: since 1994
RHEL 7: based on kernel 3.10 at first, 2014
100% rebuilds: CentOS and Scientific Linux

2. Installation

Anaconda: the installer. 3 modes: GUI, text, kickstart(for network installation, no user intervention)
KVM(kernel-based virtualization machine) is integrated into RHEL 7, to install virtual machines of Linux or Windows on RHEL 7.
RHEL 7 can be installed in network.

??? two key hardware requirements for a computer to use KVM
64 bit and support hardware virtualization.

6 virtual console screens, Ctrl+Alt+F1-F6
F1: main screen to choose language, and then changes to F6
F2: bash shell with root
F3: installation log info (/tmp/anaconda.log)
F4: storage info (/tmp/storage.log)
F5: program info (/tmp/lprogram.log)
F6: default GUI installation console

log files: first created in /tmp, then moved to `/var/log' after installation.

3. partition

/boot must be created as a standard partition outside LVM. (xfs file system, the LVM volume group is "standard partition"). /, /home if xfs, LVM volume group is vg00(customed name), and swap is of file system swap, vg00.

If we choose automatic partition, it will use LVM, and standard partition is not used.

4. IP

the address can be changed during installation.

Chapter 2 Basic Linux tools

Objectives:
- shell, commands
- archive, compress, unpack, uncompress with tar,star, gzip and bzip2.
- text files
- man, info, and /user/share/doc.

1. remote login in linux

# login
ssh -l user1 192.168.0.100
ssh user1@192.168.0.100
# GUI app
ssh -X 192.168.0.100

2. basic commands

ls -la
cd ~user2 # if user1 have execetion bit on the path
tty # show terminal name
who # check /var/run/utmp to see who is logged in now
who am i # check current user login info
w # or `what`, is like `who am i`, with more details
uptime # check uptime, system time, and how many users are logged in
whoami # show the current username
logname # show real username, even when `su`, it shows real name
which cat # show what `cat` will be run if we don't specify an absolute path

2.1 id

id shows UID, username, GID, group name, secondary groups and SELinux context.

> id
uid=0(root) gid=0(root) groups=0(root),1004(admin),1005(rvm)
> id westerngun
uid=1000(westerngun) gid=1004(admin) groups=1004(admin),10(wheel),48(apache),1005(rvm)

2.2 groups

Shows in which group the user is in. The first group: primary group. The rest: secondary group(s).

> groups $(logname)
root : root admin rvm
> groups $(whoami)
westerngun : admin wheel apache rvm

2.3 last and lastb

last check /var/log/wtmp to list all successful login attempts, system reboots.

last # list all users activities(login, logout)
last reboot # list reboots

lastb checkss /var/log/btmp and list all failed login attempts.

lastb # list all failed login

lastlog list recent login users, and users never logined.

2.4 Sysinfo

uname # system name only
uname -a # all details of system, like if it is 64 bit.
Linux local_ding 3.10.0-693.2.2.el7.x86_64 #1 SMP Tue Sep 12 22:26:13 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

hostnamectl show hostname.

hostnamectl
   Static hostname: local_host
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 5bb21648846848068840eee34f80c819
           Boot ID: 5a54d43a2efe44c28ab7c3ce9bfef00e
    Virtualization: vmware
  Operating System: CentOS Linux 7 (Core)
       CPE OS Name: cpe:/o:centos:centos:7
            Kernel: Linux 3.10.0-693.2.2.el7.x86_64
      Architecture: x86-64

hostnamectl set-hostname xxx change hostname
hostname shows current name.

2.5 Check/set date/time

timedatectl # show details
timedatectl set-time 2015-08-21 # change date. CAUTION: NOT `set-date`!
timedatectl set-time 11:00
date --set "2018-08-21 10:00" # set date and time
timedatectl list-timezones # list available timezones
timedatectl set-timezone Europe/Madrid # change timezone. No "" needed

2.6 wc: check file info

wc /etc/profile
76  252 1795 /etc/profile
|    |    |        |
|    |    |        file name
|    |    bytes/characters counts(-c)
|    word counts (-w)
line counts (-l)

2.6 List PCI, USB and CPU

lspci -v/-vv/-vvv/-m # list PCI buses and devices attached; with details
lsusb -v/-vv/-vvv # list USB buses
lscpu # list cpu info

2.7 compression(***)

tar, gzip, bzip2 are used to compress/uncompress files. tar is for archiving, gzip,bzip2 are to compress/uncompress.

gzip file1 file2 # will compress the two files in separate files

NOTE: this way will replace original files!! with .gz extension! And compress!
To uncompress, run gunzip xxx.gz or gzip -d xxx.gz.

bzip2 xxx # will comrress the file and replace original file
bzip2 -d xxx.bz2
bunzip2 xxx.bz2 # will uncompress file and delete .bz2 file

tar can archive files, preserving the attributes of files.

for example:

tar cfv /tmp/new.tar /home # archive files and save to /tmp/new.tar, without compressing
tar cfv /tmp/new.tar file1 file2
tar rvf /tmp/new.tar /etc/yum.repos.d # append the file to the tar
tar xvf /tmp/new.tar # extract the files in the tar in here (.)
tar cvfz /tmp/new.tar.gz /home # archive and compress with gzip
tar cvfj /tmp/new.tar.bz2 /home # archive and compress with bzip2

Remember: first the tar file name, then the files to package!