Uly.me

cloud engineer

centos

Check Reboot After Updates

Here’s the command to check if the system needs a reboot after running yum update.

Must be root or run it sudo.

$ needs-restarting -r ; echo $?
Core libraries or services have been updated:
  openssl-libs -> 1:1.0.2k-21.el7_9
  kernel -> 3.10.0-1160.31.1.el7
  dbus -> 1:1.10.24-15.el7
  linux-firmware -> 20200421-80.git78c0348.el7_9
  glibc -> 2.17-324.el7_9
  systemd -> 219-78.el7_9.3
 
Reboot is required to ensure that your system benefits from these updates.
 
More information:
https://access.redhat.com/solutions/27943
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In this instance, it requires a reboot due to a new kernel.

Install OpenJDK 8

Here’s the installation instructions for OpenJDK 8.

For Fedora, Redhat and Oracle Linux.

yum install java-1.8.0-openjdk

For Debian and Ubuntu.

apt-get install openjdk-8-jre

To see if the packages (symbolic links) are there, they can be found in /etc/alternatives/, at least in Redhat 7.

ls -l /etc/alternatives/

HTTPD on Redhat & Centos

Here are the commands to start, stop, enable and get the status of Apache on RHEL and CentOS.

systemctl enable httpd  # enable on bootup
systemctl status httpd  # get status
systemctl start httpd   # start
systemctl stop httpd    # stop
systemctl restart httpd # restart

OpenSSL Upgrade

Here’s how to upgrade to OpenSSL 1.1 on Redhat/Centos.

# check
openssl version
yum info openssl
# download and install
cd /usr/local/src
wget https://www.openssl.org/source/openssl-1.0.2-latest.tar.gz
tar -zxf openssl-1.0.2-latest.tar.gz
# compile
cd openssl-1.0.2a
./config
make
make test
make install
# update softlink
mv /usr/bin/openssl /root/
ln -s /usr/local/ssl/bin/openssl /usr/bin/openssl
# verify new version
openssl version

Apache & Webroot

Where’s Apache and webroot for the different distros?

Webroot:

# Redhat, Fedora, Centos, Amazon Linux
/var/www/html
# Debian, Ubuntu, Mint
/var/www/html

Apache Configuration:

# Redhat, Fedora, Centos, Amazon Linux
/etc/httpd/conf/httpd.conf
# Debian, Ubuntu, Mint
/etc/apache2/sites-available/default