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redhat14

Upgrade RHEL 6 to RHEL 7

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Here’s step by step upgrade guide for RHEL Operating System Upgrade from 6 to 7

 

Create /etc/default/grub first:

# cat /etc/default/grub

 

GRUB_TIMEOUT=10

GRUB_DISTRIBUTOR=”$(sed ‘s, release .*$,,g’ /etc/system-release)”

GRUB_DEFAULT=saved

GRUB_DISABLE_SUBMENU=true

GRUB_TERMINAL_OUTPUT=”console”

GRUB_CMDLINE_LINUX=”crashkernel=auto rd.lvm.lv=vg_cicamdb1dr/lv_root rd.lvm.lv=vg_cicamdb1dr/lv_swap ld.lvm.lv=vg_cicamdb1dr/lv_home rhgb quiet”

GRUB_DISABLE_RECOVERY=”true”

 

Patch system to latest Rhel 6.10 first and reboot

# yum clean all

# yum makecache

# yum update

# shutdown -rf now

 

Install pre-req packages for upgrade

# yum install openscap-engine-sce preupgrade-assistant* redhat-upgrade-tool

 

Delete HA related pkgs/files/dirs

# yum remove modcluster corosync luci ricci openais ccs pacemaker pcs fence-agents-all

# rm -rf /etc/cluster/cluster.conf* /etc/corosync/corosync.conf /var/log/cluster /var/log/luci /var/lib/pacemaker /etc/corosync /var/log/pcsd

 

Run the preupg command to perform the assessment of the system

# preupg    (With no options, produces result.html and tar.gz results file)

 

You can run preupg –riskcheck –verbose to view these risks

 

*Some filesystems such as /usr and /var cannot be a separate fs for the upgrade, so you need to copy the contents and remove the lvs (also remove from fstab)

 

/usr separate filesystem

https://access.redhat.com/solutions/909603

 

#  mkdir /mnt/usr/

#  mkdir /mnt/root

#  mount –bind / /mnt/root

#  mount –bind /usr /mnt/usr

#  rsync -aHAXv /mnt/usr/* /mnt/root/usr/

 

Run preupg again to verify if the risk is eliminated or not

# preupg

 

Copy ISO to client:

server:/home/user/upgrade/rhel-server-7.9-x86_64-dvd.iso

 

redhat-upgrade-tool –iso /root/rhel-server-7.9-x86_64-dvd.iso –addrepo rhel-7=http://192.168.0.1/rhel-7-server-rpms/ –cleanup-post –nogpgcheck

 

if some packages fail to upgrade and it fails out you may need to the additional repos

redhat-upgrade-tool –iso /root/rhel-server-7.9-x86_64-dvd.iso –addrepo rhel-7=http://192.168.0.1/rhel-7-server-rpms  –cleanup-post –nogpgcheck

 

if you get an error about redhat-upgrade tool outdated, then use 7.6 iso

 

yum update again to latest Rhel7

# yum clean all

# yum makecache

# yum update

 

Update GRUB2

After /etc/default/grub is created:

#grub2-mkconfig -o /boot/grub2/grub.cfg

#grub2-install /dev/sda

 

Reboot to check if it’s using grub2

 

yum update with rhel7 repos

 

Optional: If you did not use the –cleanup-post option when running the Red Hat Upgrade Tool, clean up orphaned RHEL 6 packages:

# rpm -qa | grep .el6 &> /tmp/el6.txt

# rpm -e $(cat /tmp/el6.txt) –nodeps

 

Check for dependency issue

#yum check dependencies

#yum reinstall program_name

 

Install the missing packages from rhel6

#cd /root/preupgrade

#bash noauto_postupgrade.d/install_rpmlist.sh kickstart/RHRHEL7rpmlist_kept

 

Check for clean up again

#rpm -qa | grep .el6 &> /tmp/el6.txt

#rpm -e $(cat /tmp/el6.txt) –nodeps

 

After rhel7 upgrade

systemctl stop NetworkManager && systemctl disable NetworkManager

systemctl stop firewalld.service && systemctl disable firewalld.service

 

service iptables stop

iptables.service

 
redhat13

Setup autofs on RHEL

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How to set up autofs – automount on RHEL

 

Install autofs package

yum install autofs

 

Enable, start and restart autofs daemon

systemctl enable autofs

systemctl start autofs

systemctl restart autofs

 

Configure settings of autofs

vi /etc/sysconfig/autofs

specify options to add timeout

OPTIONS=”–timeout”

 

vi /etc/auto.master

add the new auto.mount configuration file

write below /misc

/-      /etc/auto.mount

 

vi /etc/auto.mount

/nfs_mount -fstype=nfs,rw 192.168.0.50:/nfs_share

 

*Make sure to restart daemon when changing the configuration

redhat12

Setup clustering on RHEL

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To setup clustering via PCS on RHEL

 

Create cluster authentication

pcs cluster auth server1 server2 -u hacluster

 

Setup & initialize cluster and nodes

pcs cluster setup –name clusterName server1 server2

 

Set STONITH 

pcs property set stonith-enabled=true

 

 

 

 

Setting cluster parameters

 

Create ipmi users for clustering

ipmitool -U fence -I lanplus -P ‘fencePassword’ -H 192.168.0.1 sensor -L Administrator

 

iDRAC IP for IPMI

server1 (192.1.1.1)

server2 (192.2.2.2)

 

Create pcs stonith entity

pcs stonith create server1 fence_ipmilan pcmk_host_list=server1 delay=30 ipaddr=192.1.1.x login=fence passwd=password  privlvl=Operator lanplus=1 op monitor interval=60s

pcs stonith create server2 fence_ipmilan pcmk_host_list=server2 ipaddr=192.0.0.x login=fence passwd=password privlvl=Operator lanplus=1 op monitor interval=60s

 

Configure corosync

edit /etc/corosync/corosync.conf to have rrp_mode:active & add new ring#_addr to make redundancy

restart corosync

“corosync-cfgtool -s” to check

 

Create Virtual IP Address

pcs resource create virtual_ip ocf:heartbeat:IPaddr2 ip=192.1.1.x cidr_netmask=32 nic=bond0 op monitor interval=30s

 

Create ping gateway

pcs resource create ping_gateway_db ocf:pacemaker:ping host_list=192.1.1.1

 

Create LVM

pcs resource create vg_serviceName LVM volgrpname=serviceName exclusive=true

 

Edit the lvm.conf file to mount LVM

use_lvmetad = 0 on all nodes

locking_type = 1 on all nodes

 

        volume_list = [ “local_volume_group” ]

 

# systemctl stop    lvm2-lvmetad

# systemctl disable lvm2-lvmetad

# systemctl mask lvm2-lvmetad.socket

 

# cp /boot/initramfs-$(uname -r).img /boot/initramfs-$(uname -r).img.$(date +%m-%d-%H%M%S).bak

# dracut -f -v

 

Oracle Filesystems

pcs resource create fs_serviceName Filesystem device=”/dev/mapper/service-oracle” directory=”/oracle/serviceName” force_unmount=”true” fstype=”ext4″ run_fsck=”no”

pcs resource create fs_oracle_data1 Filesystem device=”/dev/mapper/serviceName-oradata1″ directory=”/oracle/serviceName/oradata1″ force_unmount=”true” fstype=”ext4″ run_fsck=”no”

pcs resource create fs_oracle_data2 Filesystem device=”/dev/mapper/serviceName-oradata2″ directory=”/oracle/serviceName/oradata2″ force_unmount=”true” fstype=”ext4″ run_fsck=”no”

 

Oracle instance & listener

pcs resource create db-oracle-instance oracle sid=”Oracle_ID” home=/oracle/serviceName/19_64 monuser=”monuser” monpassword=”password” user=”serviceUser” monprofile=”default”

 

*serious issue if home= variable has / at the end

*https://dbvisit.com/blog/connected-to-an-idle-instance-but-database-is-running

 

pcs resource create db-oracle-listener ocf:heartbeat:oralsnr home=/oracle/serviceName/19_64 listener=LISTENER_serviceName sid=”Oracle_ID” tns_admin=/oracle/serviceName/19_64/network/admin user=”serviceUser” op methods interval=0s timeout=5 monitor interval=10 timeout=30 start interval=0s timeout=120 stop interval=0s timeout=120

 

Resource group

pcs resource group add group_name resource_id…

pcs resource group add service-db-vip ping_gateway_db vg_serviceName fs_gspnb fs_oracle_data1 fs_oracle_data2  db-oracle-instance db-oracle-listener

 

Add constraint

location add <id> <resource> <node> <score>

pcs constraint location add server1 ServiceName server1 20000

pcs constraint location add server2 ServiceName server2 10000

 

location add <id> <resource> <node> <score>

pcs constraint location add location-server2-server1-INFINITY server2 server1 INFINITY

pcs constraint location add location-server1-server2-INFINITY server1 server2 INFINITY

 

Set up logical volume management

volume_list attribute should be commented on /etc/lvm/lvm.conf

#volume_list=[~~~~~]

 

Clean up failure messages

pcs resource cleanup [resource id]

 

During & After system migration

disable stonith during configuration to prevent fencing

pcs property set stonith-enabled=false

 

set fence reaction to panic after migration

pcs property set fence-reaction=panic

 

Show constraint

pcs constraint show –full

 

Add stickiness on resource meta

stickiness is value to indicate how much the resource prefers to stay where it is

stickiness is like the “cost” of moving resource groups

to see current score on each resource group

pcs constraint show –full

EX:  Resource: GSPNB

    Enabled on: gspnbldb (score:20000) (id:gspnb1)

    Enabled on: gspndev (score:10000) (id:gspnb2)

 

to set the stickiness

pcs resource meta <ResourceGroup> resource-stickiness=[NumberValue] priority=[NumberValue]

pcs resource meta GSPNB resource-stickiness=15000 priority=100

 

this will allow the resource to move when “move” command is issued, otherwise it will stick to failover node

calculation:

score of 20000 > score of 10000 so it’ll stay at gspnbldb

once you issue failover or move command, it will create ban constraint to not allow moving back

“move” option on pcs is to “move the  resource  off  the  node  it  is currently running on by creating a -INFINITY location constraint to ban the node” (it ain’t coming back…)

the stickiness cost of 15000 can be added to help move 10000+15000 > 20000 to push failover node to move back to original node

 

Remove constraint

you need to remove constraint that may have been created during resource group move OR failover (it will not failback otherwise)

pcs constraint remove <constraint_id>

 

To test fencing

it will shutdown the node specified and remove node from clustering system

pcs stonith fence [NodeName]

 

 

 

*cheat sheet on RedHat Linux Guru

 

 

redhat11

Setup Samba Server on RHEL

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How to set up Samba Service

 

Install appropriate packages

yum install samba* -y

 

Enable samba daemon on reboot

systemctl enable smb

 

To start & stop smb daemon

systemctl start smb

systemctl start nmb

 

Create samba share directory

mkdir /smb_share/

 

Set SELinux Policy

semanage fcontext -a -t samba_share_t “/smb_share(/.*)?”

restorecon -vRF /smb_share/

 

Create samba server user

useradd smbuser

 

Setup samba server user’s password

smbpasswd -a smbuser

 

Setup the samba share directory’s owner

chown smbuser:root /smb_share/

 

Edit sam database

pdbedit -L -v

 

Configure samba daemon

vi /etc/samba/smb.conf

[smb_share]

        comment = SMB Share from Linux

        path =/smb_share

        browsable = yes

        valid user = smbuser

        writable = yes

 

redhat10

File Access Control List on RHEL

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Granting an additional user read/write/execute access

setfacl -m u:marvin:rwx file_name

 

Revoking write access from all groups and all named users

setfacl -m m::rx file_name

 

Removing a named group entry from a file’s ACL

setfacl -x g:staff file_name

 

Copying the ACL of one file to another

getfacl file_name | setfacl –set-file=- file_name

 

Copying the access ACL into the default ACL

getfacl –access dir | setfacl -d -M- dir

 

Remove all ACL entries

setfacl -b file_name

redhat09

VNC service on RHEL

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How to use VNC Server (like RDP on Windows)

 

Configure the settings on GDM (GNOME Display Manager)

vi /etc/gdm/custom.conf

enable WaylandEnable=false

 

Install appropriate packages

yum install tigervnc-server tigervnc-server-module tigervnc -y

 

Set the password by below

su – into the user

vncpasswd

viewonly = no

 

Copy the template file to the systemd

cp /usr/lib/systemd/system/vncserver@.service /etc/systemd/system/vncserver@.service

 

Configure the template file to meet the user set above

Type=forking

WorkingDirectory=/home_directory

User=UserName

Group=UserGroupName

PIDFile=/home_directory/.vnc/%H%i.pid

 

ExecStartPre=/bin/sh -c ‘/usr/bin/vncserver -kill %i > /dev/null 2>&1 || :’

ExecStart=/usr/bin/vncserver -autokill %i

ExecStop=/usr/bin/vncserver -kill %i

 

Disable SELinux

vi /etc/selinux/config

SELINUX=disabled

setenforce=0

getenforce=Permissive

 

 

Enable firewall for ports

firewall-cmd –permanent –add-service=vnc-server

firewall-cmd –reload

 

Start VNC service

systemctl daemon-reload

systemctl enable vncserver@:1

systemctl start vncserver@:1

 

Connect using any of VNC view system to connect to the GUI

 

redhat08

Package management on RHEL

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To install without making it default package

 

Download the package only without install

yum install –downloadonly “PackageName”

 

downloaded package will go to /var/cache/yum/x86_64/7/updates/packages/

 

Download and install without configuration

yum install -I “PackageName” –noscripts   <– no I or noscript option… moving on to rpm command

rpm -i “PackageName” –noscripts   <– installs without going through the install scripts for configuration

 

To check which version is current default

/etc/sbin/alternatives –config “PackageName”

 

*please note that –noscripts option will not create the alternative listing for /usr/sbin/alternatives

 

we can add the program path as alternative name

update-alternatives –install “name” “path”

 

we can set the program to default by

update-alternatives –set “name” “path”

 

to view the scripts that runs while installing, do

rpm -qp –scripts PackageName.rpm

 

Here’s helpful commands on RPM

Installing

rpm -ivh <package_path>

Updating

rpm -Uvh <package_path>

Uninstalling

rpm -e <package_path>

List/Query

rpm -qa | grep <package_name>

Determine package

rpm -qf /etc/passwd

 

Here’s helpful commands on YUM

Installing

yum install <package_name>

Updating

yum update <package_name>

Uninstalling

yum remove <package_name>

List/Query

yum list -installed

Determine package (finds the package based on the given file)

 

yum provides /etc/passwd

redhat07

Make swap memory on RHEL

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Make new swap memory space

fdisk to disk

create new partition with Linux swap type

partprobe to update partition table to OS

mkswap “disk_path”

mkswap /dev/sda1

swapon -s (status)

swapon -a (activate)

 

Remove new swap space

swapoff “disk_path”

swapon -s (status)

 

Verify the new swap space

blkid and check the type “swap”

 

Detail statistic on how many pages are in &out of the memory

sar -A

 

redhat06

External storage on RHEL

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Here’s how you can connect and communicate with external storage on RHEL

 

We will be using multipath daemon

 

To list all the LUNs attached to host

multipath -ll 

 

To reload multipath

service multipathd reload

 

To list and check status of the FC cards

systool -c fc_host -v

 

To rescan for new LUNs

/usr/bin/rescan-scsi-bus.sh

OR

echo “1” > /sys/class/fc_host/host#/issue_lip

echo “1” > /sys/class/fc_host/host#/issue_lip

 

redhat05

Logical Volume Management on RHEL

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Here’s guide on how to work with logical volume management on RHEL

 

To see & rescan physical volumes

pvs

pvscan

 

To see & rescan volume group

vgs

vgscan

 

To see & rescan logical volumes

lvs

lvscan

 

 

 

 

Here’s guide on how to increase the logical volume

lvresize -r -L + ##G /dev/myvg/mylv (extend by gigabyte)

lvresize -r -l +#### /dev/myvg/mylv (extend  by bytes)

lvresize -r -l +100%FREE /dev/myvg/mylv (extend by percentage)

or

lvextend -L #G /dev/myvg/mylv (set to specific  size by gigabyte)

lvextend -L +#G /dev/myvg/mylv (extend  by bytes)

lvextend -l +100%FREE /dev/myvg/mylv (extend by percentage)

 

*lvextend will not show any free space after the execution.

 

*try to run the command “resize2fs /dev/mapper/logicalVolumePath/” and check df -Ph to verify that they have free space afterwards

 

 

 

 

Here’s guide on how to reduce the logical volume

1. Shutdown all applications/databases which are hosted in the logical volume management

2. Complete the backup

3. Unmount the file system

4. Hashout the file system entry in /etc/fstab

5. It’s only applicable for ext2/ext3/ext4

6. Check for any errors (e2fsck -f “logical_volume_path”)

ex: e2fsck -f /dev/mapper/rhel_vg-lv0

7. Reduce the file system (resize2fs “logical_volume_path” “want_to_become_size”)

ex: resize2fs /dev/mapper/rhel_vg-lv0 1G

8. Reduce the logical volume size (lvreduce -L “want_to_become_size” “logical_volume_path”)

ex: lvreduce -L 1G /dev/mapper/rhel_vg-lv0

9. Uncomment on /etc/fstab

10. Mount the file system

 

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