AlmaLinux

Posted on April 9, 2025 by admin

Sometimes it can be helpful to have a specific docker version that doesn’t change with a dnf update. To manually set the docker version, do the following.

Install dnf versionlock

dnf install 'dnf-command(versionlock)'

Next, lock the version for Docker and the Docker CLI.

dnf versionlock add docker-ce-3:27.5.0 docker-ce-cli-1:27.5.0

If you need to downgrade docker, you can do that with the following.

dnf downgrade docker-ce-3:27.5.0 docker-ce-cli-1:27.5.0

That should be it. If you want to check and see what packages are locked, run

dnf versionlock list

Example output:

Last metadata expiration check: 0:01:39 ago on Tue 08 Apr 2025 01:01:10 AM UTC.
docker-ce-3:27.5.0-1.el9.*
docker-ce-cli-1:27.5.0-1.el9.*

How to the Uninstall Elastic Agent on Linux

Posted on February 28, 2025 by admin

Go to “Kibana/app/fleet/agents”

Click the 3 dots on the host and select uninstall agent.

Select the command to uninstall and run it on the host.

Finally hit the three dots and unenroll agent.

Add warning for emails from external domains in cPanel/WHM

Posted on December 9, 2024 by admin

In this post we are going to setup Exim to add “[External]” to the email subject if it originates from outside of the local domain.

Thanks to Sam for this post. It was extremely helpful.
https://tech.saqr.org/2020/01/for-incoming-email-not-from-our-domain.html

Steps

Create a new Exim Filter
Enable Filter

Create an Exim Filter

SSH to the server and create a Exim filter. In cPanel there are in /usr/local/cpanel/etc/exim/sysfilter/options/. You can name the filter what ever you want.

vi /usr/local/cpanel/etc/exim/sysfilter/options/external_email_warning

Change “incredigeek.com” to your domain name.
You can also change “[External]” to whatever you want to be prepended to the subject.

if
  $header_to: contains "@incredigeek.com>"
  and $header_from: does not contain "@incredigeek.com>"
  and $header_subject: does not contain "[External]"
then
  headers add "Old-Subject: $h_subject:"
  headers remove "Subject"
  headers add "Subject: [External] $h_old-subject"
  headers remove "Old-Subject"
endif

Save the file.

Enable Custom Exim Filter

Now log into WHM, go to Service Configuration > Exim Configuration Manager > Basic Editor > Filters

At the bottom of the filters, you should see a new “Custom Filter: external_email_filter”
This is the filter you just created. Make sure it is On, and Save changes.

Enable Custom Exim Email Filter for External Email

There you go! Any email you receive now that is from an external domain should now have “[External]”, or whatever you specified, prepended to the subject.

If you run into any errors, try reviewing the panic log to see if there are any syntax errors.

Troubleshooting

You can use tail to follow the panic log to verify you have all the syntax correct.

tail /var/log/exim_paniclog -f

Fix PowerDNS “Old-style settings syntax not enabled”

Posted on November 19, 2024 by admin

The PowerDNS Recursor started supporting YAML for configs in version 5.0.0. YAML is the default as of 5.2.0. You can still use the old config if --enable-old-settings is provided as a command line option when starting PowerDNS. If that option is not being used, and you are using the old config, you will experience the following errors.

msg="Old-style settings syntax not enabled by default anymore. Use YAML or enable with --enable-old-settings on the command line" subsystem="config" level="0" prio="Error" tid="0" ts="1732025541.126" configname="/etc/pdns-recursor/recursor.conf"

msg="YAML config found, but error occurred processing it" error="invalid type: string \"allow-from=127.0.0.0/8, 10.0.0.0/8, 192.168.0.0/16", expected struct Recursorsettings at line 17 column 1" subsystem="config" level="0" prio="Error" tid="0" ts="1732025541.817" configname="/etc/pdns-recursor/recursor.conf"

Fortunately, this is an easy fix.

Convert old config to YAML with rec_control.
Save as new YAML config.
Remove old config.
Start pdns-recursor.

Convert Config to YAML

The rec_control command can convert our old style config to a YAML config. This should automatically pull the default config in /etc/pdns-recursor/recursor.conf.

rec_control show-yaml

Save output to /etc/pdns-recursor/recursor.yml

Remove the Old Style Config

We can remove the old config by renaming it, or deleting it.

mv /etc/pdns-recursor/recursor.conf /etc/pdns-recursor/recursor.conf.oldstyle

rm /etc/pdns-recursor/recursor.conf

Start the PowerDNS Recursor

Start the pdns-recursor service using the systemctl command.

sudo systemctl start pdns-recursor

Verify there are no errors

sudo systemctl status pdns-recursor

How to Migrate Email without IMAP credentials

Posted on October 31, 2024 by admin

Here are a few ways you can migrate emails without knowing the IMAP credentials.

Use the Admin Password.
Migrate emails using SFTP.
Import/Export using RoundCube?

Use the Admin Password

Some email services allow you to use the administrator password to sign into any email account. This allows you to move emails without knowing the users password.

You can refer to this FAQ on the imapsync website.

https://imapsync.lamiral.info/FAQ.d/FAQ.Admin_Authentication.txt

Migrating Files using SFTP

Disclaimer:

This option will only work if you have ftp/ssh/filesystem access.
Depending on email volume, you could miss emails that arrive during the transition.
If possible, it is recommended to use something like imapsync.
There could be format issues if the two email servers use different mailbox formats and/or email server software.

Emails are usually stored in the users home directory. Depending on the hosting provider, it could be /mail or ~/mail

You can zip up the mail directory and then unzip on the target server. This would only work if you have access to the filesystem. Create your email accounts before unzipping.

You could transfer the passwd and shadow files to keep the email passwords the same. Again, create the email addresses on the target server first and then either overwrite, or merge the differences between the shadow and passwd files.

For example, on cPanel servers, the mail directory is in ~/mail and the shadow and passwd files are in ~/etc/DOMAIN.COM

If you are logged in as root, you will need to change ~/ to /home/USER/ substituting USER for the actual cPanel user.

Import/Export messages from RoundCube?

You can import and export emails using the RoundCube webmail interface. However, the export is limited to one. message. at. a. time. This could work for a handful of messages, but can get quite tedious if you have a large number of emails.

How to Set up a PowerDNS Recursor

Posted on August 6, 2024 by admin

The following are the steps needed to install a PowerDNS recursor on RHEL, Fedora, Rocky Linux, or AlmaLinux

Install from package manager with

yum install pdns-recursor

Allow DNS through Firewall

sudo firewall-cmd --add-service=dns --permanent

Configure the `/etc/pdns-recursor/recursor.conf` file. The local-address is the DNS recursor, the allow-from, are the addresses you would like to allow access to

local-address=192.0.1.2
allow-from=192.0.0.0/16, 10.0.0.0/8

Start and enable the `pdns-recursor` service

systemctl enable --now pdns-recursor

https://doc.powerdns.com/recursor/getting-started.html

Ansible not working on RockyLinux 8, AlmaLinux 8, RHEL 8

Posted on August 1, 2024 by admin

[WARNING]: Unhandled error in Python interpreter discovery for host localhost: Expecting value: line 1
column 1 (char 0)

https://github.com/ansible/ansible/issues/83357

Ansible 2.17 moved to using Python 3.7. This causes issues with systems that use Python 3.6 (i.e., RHEL 8 based distros). Unfortunately, you can’t just upgrade Python either, as 3.6 is used in system tools such as DNF/YUM.

There are two options.

Upgrade to a RHEL 9 based distribution
Use Ansible 2.16

Ansible 2.16 should be the default installed version on RHEL 8 based distros.

Migrate CentOS 7 to AlmaLinux 8

Posted on July 31, 2024 by admin

The steps are taken from this page https://wiki.almalinux.org/elevate/ELevating-CentOS7-to-AlmaLinux-9.html

To upgrade to AlmaLinux 9, you will need to migrate to AlmaLinux 8 first.

sudo curl -o /etc/yum.repos.d/CentOS-Base.repo https://el7.repo.almalinux.org/centos/CentOS-Base.repo
sudo yum upgrade -y

Once yum finishes, reboot

sudo reboot

Now install elevate-release and leapp packages

sudo yum install -y http://repo.almalinux.org/elevate/elevate-release-latest-el$(rpm --eval %rhel).noarch.rpm
sudo yum install -y leapp-upgrade leapp-data-almalinux

Let’s run a pre upgrade check to see if there are any errors.

sudo leapp preupgrade

If everything checked out ok, proceed with the upgrade.

sudo leapp upgrade

Once finished, reboot.

sudo reboot

Once the system is booted, verify it upgraded.

cat /etc/*release

Problems

https://wiki.almalinux.org/elevate/ELevate-frequent-issues

LUKS

If you are using LUKS and encounter an error, check out the following link.

https://www.it-hure.de/2024/02/update-alma-rhel-with-leapp-and-luks/

You can disable the check with the following command.

rm -rf /usr/share/leapp-repository/repositories/system_upgrade/common/actors/inhibitwhenluks

More space needed on / filesystem

Try setting LEAPP_OVL_SIZE to 4096

export LEAPP_OVL_SIZE=4096

Then launch the upgrade with

sudo --preserve-env leapp upgrade

https://forums.almalinux.org/t/at-least-48mb-more-space-needed-on-the-filesystem-running-leapp-upgrade/3808/2

You can also try removing files to create more free space.

https://github.com/oamg/leapp/issues/778

Upgrading to 8.8 (Or 8.4)

For the same reason, we recommend upgrading your CentOS 7 machine to AlmaLinux OS version 8.8. To do so, you need to navigate to the /etc/leapp/files/ directory and edit the leapp_upgrade_repositories.repo to lower the AlmaLinux version in baseurl/mirror to 8.8.

The 8.8 repositories are archived. To upgrade to AlmaLinux 8.8, change ‘/etc/leapp/leapp_upgrade_repositories.repo” to the following.

[almalinux8-BaseOS]
name=AlmaLinux 8 - BaseOS
baseurl=https://vault.almalinux.org/8.8/BaseOS/$basearch/os/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-AlmaLinux

[almalinux8-AppStream]
name=AlmaLinux 8 - AppStream
baseurl=https://vault.almalinux.org/8.8/AppStream/$basearch/os/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-AlmaLinux

[almalinux8-PowerTools]
name=AlmaLinux 8 - PowerTools
baseurl=https://vault.almalinux.org/8.8/PowerTools/$basearch/os/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-AlmaLinux

[almalinux8-HighAvailability]
name=AlmaLinux 8 - HighAvailability
baseurl=https://vault.almalinux.org/8.8/HighAvailability/$basearch/os/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-AlmaLinux

[almalinux8-ResilientStorage]
name=AlmaLinux 8 - ResilientStorage
baseurl=https://vault.almalinux.org/8.8/ResilientStorage/$basearch/os/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-AlmaLinux

[almalinux8-Extras]
name=AlmaLinux 8 - Extras
baseurl=https://vault.almalinux.org/8.8/extras/$basearch/os/
enabled=1
gpgcheck=1
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-AlmaLinux

If you have issues, you may consider upgrading to 8.4 first. To do that, change 8.8 to 8.4, and comment out the ResilientStorage section.

GPG Key failing after upgrade

Try importing the AlmaLinux 8 GPG key

rpm --import https://repo.almalinux.org/almalinux/RPM-GPG-KEY-AlmaLinux

https://almalinux.org/blog/2023-12-20-almalinux-8-key-update

Securely Delete Files on Linux

Posted on June 21, 2024 by admin

We can use srm to securely delete files on Linux.

Install srm with

sudo apt install secure-delete

We can now securely delete files by running

srm filetodelete.txt

# srm --help
srm v3.1 (c) 1997-2003 by van Hauser / THC <vh@thc.org>

Syntax: srm [-dflrvz] file1 file2 etc.

Options:
        -d  ignore the two dot special files "." and "..".
        -f  fast (and insecure mode): no /dev/urandom, no synchronize mode.
        -l  lessens the security (use twice for total insecure mode).
        -r  recursive mode, deletes all subdirectories.
        -v  is verbose mode.
        -z  last wipe writes zeros instead of random data.

srm does a secure overwrite/rename/delete of the target file(s).
Default is secure mode (38 writes).
You can find updates at http://www.thc.org

Other links for securely erasing drives.
https://www.tomshardware.com/how-to/secure-erase-ssd-or-hard-drive

Top 8 Nmap options

Posted on June 20, 2024 by admin

Here are 8 excellent Nmap options, what they do, and why you would use them.

Most of the options can be run together. You will normally want to perform scans with administrator or root privileges.

	Option	What is does	Why you would use
1.	-sn	No port scan	Helpful for quickly discovering hosts that are up
2.	-iL file.lst	Scan IP addresses in file.lst	Helpful if you already have a list IP addresses to scan
3.	-n	Skip reverse DNS lookup	This can help speed up scanning
4.	-Pn	Pretend host is up	Use when hosts have Ping disabled. e.g. Windows
5.	-O	OS detection	Use to detect OS version
6.	-T4	Speed up scan	Increases scan speed (Default is -T3)
7.	-A	Aggressive scan options	Shorthand option. Enables OS detection (-O), version Scanning (-sV), script scanning (-sC), and runs a traceroute
8.	-oA filename	Save output to ALL formats	This saves the output to separate files for XML and grepable formats

Nmap table: 8 common options.

Incredigeek

Category Archives: Linux