What's changed: Initial version (topic 1.01, subtopics 1.01.1–1.01.5)
1.1Installing, Booting, Connecting to, and Shutting Down Linux
Learn the basics of installing Linux on physical/virtual machines and starting, stopping, and connecting remotely: boot priority in UEFI/BIOS, install-time choices (package groups, time zone, GUI/CUI), stopping with shutdown/reboot/halt, and SSH public key authentication (authorized_keys, known_hosts).
The starting point of Linux server administration is the lifecycle: install, boot, connect, and stop correctly. Exam 101 tests these basics in practical form: installing from DVD/ISO images, connecting remotely over SSH, and shutting down safely from the command line.
1.1.1Installation and boot media priority
- Change the boot media priority in the UEFI/BIOS setup so the machine boots the DVD/USB installer. Putting optical/USB before the internal disk is the standard move.
- Key install-spec choices: package groups (for servers, minimal install plus required roles), time zone (e.g., Asia/Tokyo), root/user passwords, and GUI vs CUI.
- Servers usually run CUI (text console); GUI (desktop) is for workstation use. You can add package groups later.
1.1.2Start/stop and connect/disconnect
- Stop/restart commands: shutdown (the canonical way, with scheduling and warnings to logged-in users:
shutdown -h now,shutdown -r +5 "rebooting for maintenance"), reboot, and halt. - SSH public key authentication: create the private key
~/.ssh/id_rsaand public keyid_rsa.publocally, and register the public key in~/.ssh/authorized_keyson the server. The client's~/.ssh/known_hostsrecords the host key of servers you connect to. - Disconnect cleanly with logout, exit, or Ctrl+D (^D). Close sessions explicitly instead of leaving them open.
Exam staples: public key goes to the server's authorized_keys, host keys are recorded in the client's known_hosts, scheduled shutdown with warnings = shutdown, and prefer the proper stop procedure over cutting power. Always distinguish which machine each file lives on.
In practice: to stand up a new server, set the install media first in UEFI/BIOS, boot the ISO image, and complete installation per the spec (package groups, time zone, passwords, GUI/CUI). Day-to-day work is remote: ssh user01@server01. Accepting the fingerprint on first connect appends the host key to known_hosts; if that host's key later changes you get a warning (spoofing detection). For public key authentication—safer than passwords—generate id_rsa/id_rsa.pub with ssh-keygen and register only the public key in the server's authorized_keys. Stop with shutdown (-h halt, -r reboot, absolute/relative time, broadcast message). Note that halt may stop the CPU without powering off, and reboot is equivalent to shutdown -r now.
| File/command | Location / purpose | Key point |
|---|---|---|
| ~/.ssh/id_rsa | Client, private key | Never distribute |
| ~/.ssh/authorized_keys | Server, registered public keys | Append public keys to allow key auth |
| ~/.ssh/known_hosts | Client, records of host keys | Warns when a host key changes |
| shutdown -h / -r | Canonical stop/restart | Supports scheduling and warnings |
Trap: "register the private key (id_rsa) in the server's authorized_keys" is wrong—you register the public key (id_rsa.pub); the private key never leaves the client. "known_hosts lives on the server" is also wrong—it is a client-side record of server host keys.
1.1.3Section summary
- Install = boot priority in UEFI/BIOS, then follow the spec for package groups / time zone / GUI vs CUI
- Key auth = public key into the server's authorized_keys / host keys in the client's known_hosts / stop with shutdown
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Quick check
(just a quick review)Q1. You want to enable SSH public key login to a remote server. Which file goes where on the server?
Q2. You want to warn logged-in users and stop the system in five minutes. Which command?
Q3. Connecting over SSH as usual, you get a warning that the host key has changed. What does this mean?