EX200 Red Hat Certified System Administrator - RHCSA (8.2) Questions and Answers

groupadd adminuser

useradd natasha -G adminuser

useradd haryy -G adminuser

useradd sarah -s /sbin/nologin

Passwd user name // to modify password or echo redhat | passwd --stdin user name id natasha // to view user group.

• echo "1" >/proc/sys/net/ipv4/ip_forward
• vi /etc/sysctl.conf

net.ipv4.ip_forward = 1

If you want to use the Linux System as a Router to make communication between different networks, you need enable the IP forwarding. To enable on running session just set value 1 to

/proc/sys/net/ipv4/ip_forward. As well as automatically turn on the IP forwarding features on next boot set on /etc/sysctl.conf file.

Download the new kernel file and then install it.

[root@desktop8 Desktop]# ls

kernel-2.6.32-71.7.1.el6.x86_64.rpm

kernel-firmware-2.6.32-71.7.1.el6.noarch.rpm

[root@desktop8 Desktop]# rpm -ivh kernel-*

Preparing... ###########################################

[100%]

1:kernel-firmware

########################################### [ 50%]

2:kernel

########################################### [100%]

Verify the grub.conf file, whether use the new kernel as the default boot. [root@desktop8 Desktop]# cat /boot/grub/grub.conf default=0

title Red Hat Enterprise Linux Server (2.6.32-71.7.1.el6.x86_64)

root (hd0,0)

kernel /vmlinuz-2.6.32-71.7.1.el6.x86_64 ro root=/dev/mapper/vol0-root rd_LVM_LV=vol0/root rd_NO_LUKS rd_NO_MD

rd_NO_DM LANG=en_US.UTF-8 SYSFONT=latarcyrheb-sun16 KEYBOARDTYPE=pc KEYTABLE=us crashkernel=auto rhgb quiet

initrd /initramfs-2.6.32-71.7.1.el6.x86_64.img

yum -y install sssd authconfig-gtk krb5-workstation authconfig-gtk // open the graphical interface

Modify user account database to ldap, fill up DN and LDAP SERVER as questions required, use TLS to encrypt connections making tick, write http://server.domain11.example.com/pub/EXAMPLE-CA-CERT to download ca, authentication method choose ldap password.

You can test if the ldapuser is added by the following command:

Id ldapuser1

Note: user password doesn’t not need to set

• Use fdisk /dev/hda ->To create new partition.
• Type n-> For New partition
• It will ask for Logical or Primary Partitions. Press l for logical.
• It will ask for the Starting Cylinder: Use the Default by pressing Enter Key.
• Type the Size: +100M ->You can Specify either Last cylinder of Size here.
• Press P to verify the partitions lists and remember the partitions name. Default System ID is 83 that means Linux Native.
• Type t to change the System ID of partition.
• Type Partition Number
• Type 82 that means Linux Swap.
• Press w to write on partitions table.
• Either Reboot or use partprobe command.
• mkswap /dev/hda? ->To create Swap File system on partition.
• swapon /dev/hda? ->To enable the Swap space from partition.
• free -m ->Verify Either Swap is enabled or not.
• vi /etc/fstab/dev/hda? swap swap defaults 0 0
• Reboot the System and verify that swap is automatically enabled or not.

/etc/sysconfig/selinux

SELINUX=enforcing

• Create a partition having size 5 GB and change the syste id '8e'.
• use partprobe command
• pvcreate /dev/hda9 Suppose your partition number is hda9.
• vgextend test0 /dev/hda9 vgextend command add the physical disk on volume group.
• lvextend -L+5120M /dev/test0/lvtestvolume
• verify using lvdisplay /dev/test0/lvtestvolume.

*

[root@node2 ~]# lsblk

NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT

vdc 252:32 0 5G 0 disk

└─vdc1 252:33 0 4.1G 0 part

└─datavg-datalv 253:3 0 3.9G 0 lvm /data

vdd 252:48 0 5G 0 disk

vde 252:64 0 10G 0 disk

[root@node2 ~]# swapon -s

Filename Type Size Used Priority

/dev/dm-1 partition 2097148 1548 -2

[root@node2 ~]# free -m

total used free shared buff/cache available

Mem: 1816 1078 104 13 633 573

Swap: 2047 1 2046

[root@node2 ~]# parted /dev/vdc print

Number Start End Size Type File system Flags

1 1049kB 4404MB 4403MB primary lvm

*

[root@node2 ~]# parted /dev/vdc mkpart primary linux-swap 4404MiB 5060MiB

[root@node2 ~]# mkswap /dev/vdc2

Setting up swapspace version 1, size = 656 MiB (687861760 bytes)

no label, UUID=9faf818f-f070-4416-82b2-21a41988a9a7

[root@node2 ~]# swapon -s

Filename Type Size Used Priority

/dev/dm-1 partition 2097148 1804 -2

[root@node2 ~]# swapon /dev/vdc2

*

[root@node2 ~]# swapon -s

Filename Type Size Used Priority

/dev/dm-1 partition 2097148 1804 -2

/dev/vdc2 partition 671740 0 -3

[root@node2 ~]# blkid

/dev/vdc2: UUID="9faf818f-f070-4416-82b2-21a41988a9a7" TYPE="swap" PARTUUID="0f22a35f-02"

[root@node2 ~]# vim /etc/fstab

UUID=9faf818f-f070-4416-82b2-21a41988a9a7 swap swap defaults 0 0

[root@node2 ~]# reboot

[root@node2 ~]# swapon -s

Filename Type Size Used Priority

/dev/dm-1 partition 2097148 1804 -2

/dev/vdc2 partition 671740 0 -3

crontab -u mary -e

23 14 * * * echo "Hello World."

• vi /etc/sysconfig/network GATEWAY=192.168.0.254

OR

vi /etc/sysconf/network-scripts/ifcfg-eth0 DEVICE=eth0

BOOTPROTO=static

ONBOOT=yes

IPADDR=192.168.0.?

NETMASK=255.255.255.0

GATEWAY=192.168.0.254

• service network restart

Gateway defines the way to exit the packets. According to question System working as a router for two networks have IP Address 192.168.0.254 and 192.168.1.254.

# useradd -u 1234 alex

# passwd alex

alex111

alex111

OR

echo alex111|passwd -stdin alex

• useradd eric
• passwd eric
• vi /etc/passwd
• eric:x:505:505::/home/eric:/sbin/nologin

Which shell or program should start at login time is specified in /etc/passwd file? By default, Redhat Enterprise Linux assigns the /bin/bash shell to the users. To deny the interactive login, you should write /sbin/nologin or /bin/ false instead of login shell.

The LVM system organizes hard disks into Logical Volume (LV) groups. Essentially, physical hard disk partitions (or possibly RAID arrays) are set up in a bunch of equal sized chunks known as Physical Extents (PE). As there are several other concepts associated with the LVM system, let's start with some basic definitions:

Physical Volume (PV) is the standard partition that you add to the LVM mix. Normally, a physical volume is a standard primary or logical partition. It can also be a RAID array.

Physical Extent (PE) is a chunk of disk space. Every PV is divided into a number of equal sized PEs. Every PE in a LV group is the same size. Different LV groups can have different sized PEs.

Logical Extent (LE) is also a chunk of disk space. Every LE is mapped to a specific PE.

Logical Volume (LV) is composed of a group of LEs. You can mount a file system such as /home and /var on an LV.

Volume Group (VG) is composed of a group of LVs. It is the organizational group for LVM. Most of the commands that you'll use apply to a specific VG.

• Verify the size of Logical Volume: lvdisplay /dev/vg0/lv1
• Verify the Size on mounted directory: df -h or df -h mounted directory name
• Use: lvextend -L+400M /dev/vg0/lv1
• ext2online -d /dev/vg0/lv1 to bring extended size online.
• Again Verify using lvdisplay and df -h command.

1. Use fdisk /dev/hda-> To create new partition.

2. Type n ->For New partitions

3. It will ask for Logical or Primary Partitions. Press l for logical.

4. It will ask for the Starting Cylinder: Use the Default by pressing Enter

Keys

5. Type the size: +100M you can specify either Last cylinder of size here.

6. Press P to verify the partitions lists and remember the partitions name.

7. Press w to write on partitions table.

8. Either Reboot or use partprobe command.

9. Use mkfs -t ext3 /dev/hda?

OR

1. mke2fs -j /dev/hda? ->To create ext3 filesystem.

2. vi /etc/fstab

3. Write:

/dev/hda? /data ext3 defaults 0 0

4. Verify by mounting on current sessions also:

mount /dev/hda? /data

getenforce // Check the current mode of SELinux // SELinux runs in enforcing mode // Check

getenforce 1

getenforce

vim /etc/selinux/config selinux=enforcing // To temporarily enable SELinux

wg

sestatus

Using the browser open the URL in the question, download kernel file to root or home directory.

uname –r// check the current kernel version

rpm –ivh kernel-*.rpm

vi /boot/grub.conf// check

Some questions are: Install and upgrade the kernel as required. To ensure that grub2 is the default item for startup.

Yum repo : http://content.example.com/rhel7.0/x86-64/errata

OR

uname -r // check kernel

Yum-config-manager --add-repo=“http://content.example.com/rhel7.0/x86-64/ errata”

Yum clean all

Yum list kernel// install directly

Yum -y install kernel// stuck with it, do not pipe! Please do not pipe!

Default enable new kernel grub2-editenv list// check

Modify grub2-set-default “kernel full name”

Grub2-mkconfig –o/boot/grub2/grub.cfg// Refresh