RH124 SSH configuration

Both client and server side configuration and usage of SSH involves three packages:

• openssh-server
• openssh-clients
• openssh

We will examine these packages shortly.

Check the status of sshd.service:

$ systemctl status sshd.service
● sshd.service - OpenSSH server daemon
     Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; preset: enabled)
     Active: active (running) since Fri 2026-10-23 02:00:51 EDT; 5h 49min ago
 Invocation: 9f19b671aa534042a2785fca1a1078c5
       Docs: man:sshd(8)
             man:sshd_config(5)
   Main PID: 918 (sshd)
      Tasks: 1 (limit: 48852)
     Memory: 7.5M (peak: 24.8M)
        CPU: 119ms
     CGroup: /system.slice/sshd.service
             └─918 "sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups"

Oct 23 02:00:51 localhost.localdomain systemd[1]: Starting sshd.service - OpenSSH server daemon...
Oct 23 02:00:51 localhost.localdomain sshd[918]: Server listening on 0.0.0.0 port 22.
Oct 23 02:00:51 localhost.localdomain sshd[918]: Server listening on :: port 22.
Oct 23 02:00:51 localhost.localdomain systemd[1]: Started sshd.service - OpenSSH server daemon.
Oct 23 02:04:09 localhost.localdomain sshd-session[1924]: Accepted password for rpjday from 192.168.122.1 port 52956 ssh2
Oct 23 02:04:09 localhost.localdomain sshd-session[1924]: pam_unix(sshd:session): session opened for user rpjday(uid=1000) by rpjday(uid=0)
Oct 23 07:12:23 localhost.localdomain sshd-session[2972]: Accepted password for rpjday from 192.168.122.1 port 43614 ssh2
Oct 23 07:12:23 localhost.localdomain sshd-session[2972]: pam_unix(sshd:session): session opened for user rpjday(uid=1000) by rpjday(uid=0)
$

Stop, check and restart the service:

$ sudo systemctl stop sshd.service
$ systemctl status sshd.service
$ sudo systemctl start sshd.service

NOTE: Stopping sshd.service does not kill existing connections, just attempts at new ones.

References to man/doc pages and build IDs deleted for brevity.

NOTE: Executables under /usr/libexec are not meant to be invoked directly, but are typically “helper” utilities for other programs.

/etc/pam.d/sshd
/etc/ssh/sshd_config
/etc/ssh/sshd_config.d
/etc/ssh/sshd_config.d/40-redhat-crypto-policies.conf
/etc/ssh/sshd_config.d/50-redhat.conf
/etc/sysconfig/sshd
/usr/lib/systemd/system/ssh-host-keys-migration.service
/usr/lib/systemd/system/sshd-keygen.target
/usr/lib/systemd/system/sshd-keygen@.service
/usr/lib/systemd/system/sshd.service
/usr/lib/systemd/system/sshd.socket
/usr/lib/systemd/system/sshd@.service
/usr/lib/sysusers.d/openssh-server.conf
/usr/libexec/openssh/sftp-server
/usr/libexec/openssh/ssh-host-keys-migration.sh
/usr/libexec/openssh/sshd-keygen
/usr/libexec/openssh/sshd-session
/usr/sbin/sshd
/var/lib/.ssh-host-keys-migration

/etc/ssh/ssh_config
/etc/ssh/ssh_config.d
/etc/ssh/ssh_config.d/50-redhat.conf
/usr/bin/scp
/usr/bin/sftp
/usr/bin/ssh
/usr/bin/ssh-add
/usr/bin/ssh-agent
/usr/bin/ssh-copy-id
/usr/bin/ssh-keyscan
/usr/lib/systemd/user/ssh-agent.service
/usr/lib/systemd/user/ssh-agent.socket
/usr/libexec/openssh/ssh-pkcs11-helper
/usr/libexec/openssh/ssh-sk-helper

/etc/ssh
/etc/ssh/moduli
/usr/bin/ssh-keygen
/usr/libexec/openssh

</code> $ ls -l -rw-r–r–. 1 root root 541716 May 19 20:00 moduli -rw-r–r–. 1 root root 1916 May 19 20:00 ssh_config drwxr-xr-x. 2 root root 28 Oct 17 12:18 ssh_config.d -rw——-. 1 root root 3674 May 19 20:00 sshd_config drwx——. 2 root root 66 Oct 17 12:18 sshd_config.d -rw——-. 1 root root 480 Oct 17 12:19 ssh_host_ecdsa_key -rw-r–r–. 1 root root 162 Oct 17 12:19 ssh_host_ecdsa_key.pub -rw——-. 1 root root 387 Oct 17 12:19 ssh_host_ed25519_key -rw-r–r–. 1 root root 82 Oct 17 12:19 ssh_host_ed25519_key.pub -rw——-. 1 root root 2578 Oct 17 12:19 ssh_host_rsa_key -rw-r–r–. 1 root root 554 Oct 17 12:19 ssh_host_rsa_key.pub $ </code>

$ sudo tree -F
./
├── moduli
├── ssh_config
├── ssh_config.d/
│   └── 50-redhat.conf
├── sshd_config
├── sshd_config.d/
│   ├── 40-redhat-crypto-policies.conf
│   └── 50-redhat.conf
├── ssh_host_ecdsa_key
├── ssh_host_ecdsa_key.pub
├── ssh_host_ed25519_key
├── ssh_host_ed25519_key.pub
├── ssh_host_rsa_key
└── ssh_host_rsa_key.pub
$