#2088

[How-To] CentOS & RHEL

Olivier | How-To | 17

Create a new PV / VG / LV from an empty disk

# To retrieve the drive name 
lsblk

Create partition with fdisk

fdisk /dev/sdX
p # print partition table
n # create new partition
p # type = primary partition
ENTER # partition number (default or a value)
ENTER # default - start at beginning of disk
ENTER # 100 MB boot partiton
t # change partition's type
8e # type : Linux LVM
w # write changes

Create PV / VG / LV

# Create PV
pvcreate /dev/sdX1
vgcreate vg_NAME  /dev/sdX1
lvcreate -n lv_NAME -l 100%FREE vg_NAME
mkfs -t ext4 /dev/vg_NAME/lv_NAME # -t disk type (ext4, xfs, etc)

Edit /etc/fstab & mount drive:

/dev/mapper/vg_NAME-lv_NAME        /MOUNT_POUNT                 ext4     defaults        0 0
mkdir /MOUNT_POUNT # create mount point
mount -a # mount fstab content

———-
Extend an existing partition by adding a new disk

Create a new PV / VG / LV from an empty disk

# To retrieve the drive name 
lsblk

Create partition with fdisk

fdisk /dev/sdX
p # print partition table
n # create new partition
p # type = primary partition
ENTER # partition number (default or a value)
ENTER # default - start at beginning of disk
ENTER # 100 MB boot partiton
t # change partition's type
8e # type : Linux LVM
w # write changes

Create PV / VG / LV

# Create PV
pvcreate /dev/sdX1

#Retrieve the VG to extend with : 
vgdisplay

# Extend VG
vgextend vg_NAME  /dev/sdX1

# With the utility pvscan you can see what physical volumes are available, and how much free space there is within them
pvscan

# Extend LV
lvextend /dev/vg_NAME/lv_NAME /dev/sdX1

# Resize disk 
xfs_growfs  /dev/vg_NAME/lv_NAME
or 
resize2fs /dev/vg_NAME/lv_NAME

# Check result
lsblk
df -h

CentOS, linux, lvm, RHEL

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17 thoughts on “[How-To] CentOS & RHEL”

Olivier says:

06/07/2020 at 15:12

CentOS 7 > Disable GUI :
```
systemctl set-default multi-user.target
```
CentOS 7 > Enable GUI :
```
systemctl set-default graphical.target
```
CentOS 7 > Test if GUI is enabled :
```
systemctl get-default
```
(see also /etc/inittab)

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OLIVIER COMBE says:

10/09/2020 at 08:39

Enable optional and extras repo :

subscription-manager repos --enable=rhel-7-server-optional-rpms
subscription-manager repos --enable=rhel-7-server-extras-rpms

OLIVIER COMBE says:

25/11/2020 at 13:53

Zip a file or a folder

zip -r filename.zip folder
zip -r filename.zip folder1 folder2
zip -r filename.zip /path/to/folder1 /path/to/file2

OLIVIER COMBE says:

25/11/2020 at 13:57

Compress a folder using TAR :
```
tar zcvf file.tar.gz /home/jerry/prog
```
To preserve permissions : –preserve-permissions (-p)

The – with czf is optional.

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OLIVIER COMBE says:

17/12/2020 at 11:32

List route :
```
route
```
Add route :
```
ip route add 172.22.54.0/24 via 172.22.249.126 dev eth4
```
See also : https://www.cyberciti.biz/faq/ip-route-add-network-command-for-linux-explained/

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- OLIVIER COMBE says:
  
  08/03/2021 at 15:57
  
  https://linoxide.com/how-tos/howto-permanently-add-static-route-in-linux/
  
  Reply

OLIVIER COMBE says:

12/03/2021 at 10:32

Add color to motd :

[user@box]$ echo -en "\033[1;34m" > /etc/motd
[user@box]$ echo "Text of your motd file....." >> /etc/motd
[user@box]$ echo -en "\033[0m" >> /etc/motd

OLIVIER COMBE says:

12/07/2021 at 09:18

Install OpenVPN (client)

yum install -y yum-plugin-copr
yum install -y epel-release
yum copr enable dsommers/openvpn-release
yum install -y openvpn

OLIVIER COMBE says:

12/07/2021 at 09:29

Install netstat :
```
yum -y install net-tools
```
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OLIVIER COMBE says:

09/08/2021 at 10:40

Truncate file :
```
truncate -s 0 my_file.log
```
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OLIVIER COMBE says:

13/08/2021 at 07:56

Install python3 on RHEL 7.x:

subscription-manager repos --enable rhel-7-server-optional-rpms --enable rhel-server-rhscl-7-rpms

yum -y install @development
yum -y install rh-python36

yum -y install rh-python36-numpy rh-python36-scipy rh-python36-python-tools rh-python36-python-six

$ scl enable rh-python36 bash
$ python3 -V
Python 3.6.3

$ python -V  # python now also points to Python3 
Python 3.6.3

OLIVIER COMBE says:

13/08/2021 at 07:57

https://developers.redhat.com/blog/2018/08/13/install-python3-rhel#tl_dr

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OLIVIER COMBE says:

20/09/2021 at 10:25

see output of unattached process :
```
cat /proc/<PID>/fd/1
```
(tail is not working properly)

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OLIVIER COMBE says:

19/05/2022 at 07:16

Enable color in vi/vim in CentOS/RHEL:

yum install -y vim-enhanced

edit /etc/profile.d/vim.sh and comment the line “[ -n “$ID” -a “$ID” -le 200 ]”

if [ -n "$BASH_VERSION" -o -n "$KSH_VERSION" -o -n "$ZSH_VERSION" ]; then
  [ -x /usr/bin/id ] || return
  ID=`/usr/bin/id -u`
  #[ -n "$ID" -a "$ID" -le 200 ] && return  ### hash out this line
  # for bash and zsh, only if no alias is already set
  alias vi >/dev/null 2>&1 || alias vi=vim
fi

OLIVIER COMBE says:

09/02/2023 at 18:22

CentOS 7 > Install Python3:

yum install -y python3 python3-pip

Replace default python2 by python3

unlink /usr/bin/python 
ln -s /usr/bin/python3 /usr/bin/python 
rm -Rf /usr/bin/pip 
ln -s /usr/bin/pip3 /usr/bin/pip

OLIVIER COMBE says:

17/07/2023 at 07:44

Install nslookup:
```
sudo yum install -y bind-utils
```
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OLIVIER COMBE says:

31/08/2023 at 07:38

force unmount an NFS drive
```
umount -l /mnt
```
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[How-To] CentOS & RHEL

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17 thoughts on “[How-To] CentOS & RHEL”

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