SSH Key-Based Authentication on RHEL 9

Generate key pair (client)

ssh-keygen -t ed25519 -C "[email protected]"

Copy public key to server

ssh-copy-id -i ~/.ssh/id_ed25519.pub [email protected]

Or manually:

cat ~/.ssh/id_ed25519.pub | ssh user@server \
    "mkdir -p ~/.ssh && ch...

SSH Key-Based Authentication on Ubuntu 24.04

Generate key pair (client)

ssh-keygen -t ed25519 -C "[email protected]"

Copy public key to server

ssh-copy-id -i ~/.ssh/id_ed25519.pub [email protected]

Or manually:

cat ~/.ssh/id_ed25519.pub | ssh user@server \
    "mkdir -p ~/.ssh...

Harden OpenSSH, switch to key-based authentication and enable TOTP multi-factor authentication.

SSH Security Best Practices

At file /etc/ssh/sshd_config:

Disable Root Logins

Best: PermitRootLogin no
Good: PermitRootLogin without-password

wihout-password requires "PubkeyAuthentication yes"

Limit user Logins

AllowUsers somusername1 someusername2

Disable Protocol 1

Protocol 2

U

SSH TOTP MFA on AlmaLinux 9

Step 1 – Install PAM module

dnf install -y google-authenticator-libpam

Step 2 – Configure for each user

google-authenticator
# time-based: y, update file: y, disallow reuse: y, rate limit: y

Scan QR code with an authenticator app (Aegis, Google Authenticator, et...

SSH TOTP MFA on Arch Linux

Step 1 – Install PAM module

pacman -S --noconfirm libpam-google-authenticator

Step 2 – Configure for each user

google-authenticator
# time-based: y, update file: y, disallow reuse: y, rate limit: y

Scan QR code with an authenticator app (Aegis, Google Authenticat...

SSH TOTP MFA on Debian 12

Step 1 – Install PAM module

apt install -y libpam-google-authenticator

Step 2 – Configure for each user

google-authenticator
# time-based: y, update file: y, disallow reuse: y, rate limit: y

Scan QR code with an authenticator app (Aegis, Google Authenticator, etc....

SSH TOTP MFA on Gentoo Linux

Step 1 – Install PAM module

emerge --ask sys-auth/google-authenticator-libpam

Step 2 – Configure for each user

google-authenticator
# time-based: y, update file: y, disallow reuse: y, rate limit: y

Scan QR code with an authenticator app (Aegis, Google Authentic...

SSH TOTP MFA on NetBSD 10

Step 1 – Install PAM module

# Install google-authenticator for NetBSD 10

Step 2 – Configure for each user

google-authenticator
# time-based: y, update file: y, disallow reuse: y, rate limit: y

Scan QR code with an authenticator app (Aegis, Google Authenticator, et...

SSH TOTP MFA on OpenBSD 7.5

Step 1 – Install PAM module

# Install google-authenticator for OpenBSD 7.5

Step 2 – Configure for each user

google-authenticator
# time-based: y, update file: y, disallow reuse: y, rate limit: y

Scan QR code with an authenticator app (Aegis, Google Authenticator...

SSH TOTP MFA on RHEL 9

Step 1 – Install PAM module

dnf install -y google-authenticator-libpam

Step 2 – Configure for each user

google-authenticator
# time-based: y, update file: y, disallow reuse: y, rate limit: y

Scan QR code with an authenticator app (Aegis, Google Authenticator, etc.).

SSH TOTP MFA on Ubuntu 24.04

Step 1 – Install PAM module

apt install -y libpam-google-authenticator

Step 2 – Configure for each user

google-authenticator
# time-based: y, update file: y, disallow reuse: y, rate limit: y

Scan QR code with an authenticator app (Aegis, Google Authenticator, e...

Tune MariaDB Performance on AlmaLinux 9

my.cnf

[mysqld]
innodb_buffer_pool_size        = 4G
innodb_buffer_pool_instances   = 4
innodb_log_file_size           = 512M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method            = O_DIRECT

# Thread pool (MariaDB-specific)
thread_handling...

Tune MariaDB Performance on Arch Linux

my.cnf

[mysqld]
innodb_buffer_pool_size        = 4G
innodb_buffer_pool_instances   = 4
innodb_log_file_size           = 512M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method            = O_DIRECT

# Thread pool (MariaDB-specific)
thread_handling...

Tune MariaDB Performance on Debian 12

my.cnf

[mysqld]
innodb_buffer_pool_size        = 4G
innodb_buffer_pool_instances   = 4
innodb_log_file_size           = 512M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method            = O_DIRECT

# Thread pool (MariaDB-specific)
thread_handling...

Tune MariaDB Performance on Gentoo Linux

my.cnf

[mysqld]
innodb_buffer_pool_size        = 4G
innodb_buffer_pool_instances   = 4
innodb_log_file_size           = 512M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method            = O_DIRECT

# Thread pool (MariaDB-specific)
thread_handling...

Tune MariaDB Performance on NetBSD 10

my.cnf

[mysqld]
innodb_buffer_pool_size        = 4G
innodb_buffer_pool_instances   = 4
innodb_log_file_size           = 512M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method            = O_DIRECT

# Thread pool (MariaDB-specific)
thread_handling...

Tune MariaDB Performance on OpenBSD 7.5

my.cnf

[mysqld]
innodb_buffer_pool_size        = 4G
innodb_buffer_pool_instances   = 4
innodb_log_file_size           = 512M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method            = O_DIRECT

# Thread pool (MariaDB-specific)
thread_handling...

Tune MariaDB Performance on RHEL 9

my.cnf

[mysqld]
innodb_buffer_pool_size        = 4G
innodb_buffer_pool_instances   = 4
innodb_log_file_size           = 512M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method            = O_DIRECT

# Thread pool (MariaDB-specific)
thread_handling...

Tune MariaDB Performance on Ubuntu 24.04

my.cnf

[mysqld]
innodb_buffer_pool_size        = 4G
innodb_buffer_pool_instances   = 4
innodb_log_file_size           = 512M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method            = O_DIRECT

# Thread pool (MariaDB-specific)
thread_handling...

Tune MySQL Performance on AlmaLinux 9

my.cnf

[mysqld]
innodb_buffer_pool_size        = 4G
innodb_buffer_pool_instances   = 4
innodb_log_file_size           = 512M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method            = O_DIRECT
max_connections                = 200
thread_cache_size...

Tune MySQL Performance on Arch Linux

my.cnf

[mysqld]
innodb_buffer_pool_size        = 4G
innodb_buffer_pool_instances   = 4
innodb_log_file_size           = 512M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method            = O_DIRECT
max_connections                = 200
thread_cache_size...

Tune MySQL Performance on Debian 12

my.cnf

[mysqld]
innodb_buffer_pool_size        = 4G
innodb_buffer_pool_instances   = 4
innodb_log_file_size           = 512M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method            = O_DIRECT
max_connections                = 200
thread_cache_size...

Tune MySQL Performance on Gentoo Linux

my.cnf

[mysqld]
innodb_buffer_pool_size        = 4G
innodb_buffer_pool_instances   = 4
innodb_log_file_size           = 512M
innodb_flush_log_at_trx_commit = 1
innodb_flush_method            = O_DIRECT
max_connections                = 200
thread_cache_size...