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AIX system boot

During the boot process, the system checks the hardware, loads and runs the operating system, and configures the device. In order to guide the operating system

Tong, the following resources are required:

A boot image that can be loaded after the machine is powered on or reset. Access to root and / user file systems.

There are three ways to guide.

Hard disk boot

Diskless network boot

Service maintenance guidance

The system finds all the necessary boot process information on the disk drive. When the system is started by turning on the power switch (cold boot) or rebooted using the reboot or shutdown command, some events occur before the system becomes available. These events can be divided into the following stages

Read-only memory (ROS) kernel initialization phase

This phase will check the motherboard for problems, and the ROS initializer load will search for a list of boot devices. Once the list of boot devices is found, the boot image is read into memory and system initialization begins. Basic equipment configuration phase

This phase configures all devices with the help of the cfgmgr command. System boot phase

During this stage of the boot process, all logical volumes are activated, page scheduling is started, and / etc/inittab files are processed.

The PCI RS/6000 system uses sound and images to show the different stages of the boot process. For example, whenever you power on, as soon as the processor is activated, it will beep, and when the system memory check is complete, it will display the icon of PowerPC (or text), as well as the icon of all devices with legitimate addresses. After the display of the device icon is over, if the ROS of the system is not destroyed, it will beep again.

The alog command maintains and manages logs

The rc.boot script explicitly redirects the boot information to the file / var/adm/bootlog through the alog command. If something goes wrong somewhere in the system, you can boot the system into single-user mode (also called maintenance mode) and access these logs through the alog command to see at which stage the problem occurs.

Alog command

-f xx specifies the log file name

-L lists the log types currently defined in the alog configuration database.

-Q copy standard input to log file

-f xx-o list the contents of the xx log file

The-t log type identifies a log defined in the alog configuration database

(alog-0-t log type (view a certain type of log))

Alog files have no concurrency control; therefore, if multiple processes try to write the same file at the same time, the contents of the log file may be different than expected. Besides, it's a cycle.

Therefore, when its maximum size is reached, it will be overwritten by the overwrite

During the boot process, the system must determine which resources are available. For example, the system must determine what kind of bus it is using, what types of devices are connected to it, where the rootvg is located, and so on. The configuration of these devices is handled by the BOS command cfgmgr. The cfgmgr command configures the device and selectively installs the device software into the system.

Cfgmgr configuration Manager

The configuration of the device is divided into three stages, stage 1, stage 2 (for normal mode boot), and phase 3 (for service mode boot)

During the system boot process, the cfgmgr command configures all devices necessary to use the system. System booting consists of two phases. Phase 1 begins when the kernel (kernel) is imported into the system and the boot file system (boot file system) is initialized. In this phase, the cfgmgr command is invoked with the-f flag to specify this phase as phase 1. The cfgmgr command runs the configuration rules for all Phase 1 to configure the basic device. Phase 2 at this stage, the cfgmgr command is invoked with the-s flag. The cfgmgr command recognizes the configuration rules for three phases: phase 1, phase 2 (the second boot phase in regular mode boot), phase 3 (the second boot phase in maintenance mode boot), and the configuration rules are also a set of executable programs. A configuration rule must consist of the following three items: 1. Phase: at which stage the program specified by the rule runs. two。 Priority: the order in which the rules are run at the same stage. 3. Program: an executable program corresponding to a rule. Priority is a positive integer, and the smaller the number, the higher the priority. The programs contained in the configuration rules stored in the configuration database must be executable programs with full paths. Cfgmgr-f executes all phase one configuration rules, and this parameter cannot run-s after system startup to execute all phase two configuration rules-p xx runs the location of the specified phase xx-I xxx installation media Or the location of the software package-l xxx configuration specifies the device name and all devices connected to it (descendant devices)-v outputs detailed information it will produce an output cfgmgr command similar to the alog-o-t boot command that cannot be interrupted the cfgmgr command configures only those devices that are powered on at system startup and are self-configurable

Last command

The last command is typically used to display all previous login and logout actions recorded in the / var/adm/wtmp file in reverse chronological order. The / var/adm/wtmp file collects their records when login and acctcon2 events occur and retains them until the records are disposed of by the login and acctcon2 commands as part of the daily reporting program.

Login and logout of last name name users xxx Login and logout specified on the terminal specified by the xxx parameter-NUMBER specifies the number of lines to display in the output the last command can also be used to determine when the system was last shut down. The syntax of this command is: last shutdown

Bootlist command

The bootlist command allows you to display and replace a list of boot devices that can be used to boot the system. When the system is booted

It scans the devices in the list and attempts to boot from the first device it discovers that contains a boot image.

Bbotlist supports modifications to the Normal boot list general mode boot list that specifies the possible boot devices when the system is to be booted into normal mode. The Service boot list maintenance mode boot list specifies the possible boot devices when the system is to be booted into service mode. The Previous boot device previous boot device list specifies the device that was last used to boot the system. Some hardware platforms may try the previously used boot device to boot before looking for a boot device from one of the previous two lists

Bootlist

-m xxx: specifies which boot list to display or modify. Possible values for xxx include normal, service,both, or prevboot.

-f xxx: reads information from the specified file

-o: displays the boot list specified by-m

If you need to make changes to your regular boot list, use the following command: bootlist-m normal device 1 name device 2 name. Boot device selection: each device you add to the boot list must be in the AVAILABLE state. Otherwise, the bootlist command will fail And you will encounter an error similar to the following: valid device name for the 0514-210 bootlist: Device xxxxx is not in the AVAILABLE statbootlist command device description fdxx disk drive device logic name hdiskxx physical volume device logic name cdxx SCSI CD-ROM device logic name rmtxx tape device logic name entxx Ethernet The Ethernet adapter logical name tokxx token Ring (Token ring) adapter logical name uptime command will show how long the system has been running (in the up state). The uptime command outputs the current time, the length of time the system has been running, the number of online users, and the load average shutdown command-d shuts down the system and moves from distributed mode (distributed mode) to multi-user mode (multiuser mode). -F shuts down quickly, bypasses the process of sending messages to other users, and shuts down the system as soon as possible. -h stops the operating system completely; it works the same as the-v flag. -I specifies that interactive mode (interactive mode) is used. Display interactive information to guide the user to shut down. -k avoid shutting down the system. -m shut down the system and switch to maintenance (single user) mode. -r restart the system after shutting down with the reboot command. -v completely stop the operating system. Common boot LEDs: LED 201-corrupted boot image LED 223-229-invalid boot lists LED 551,555, and 557-errors including file system corruption and JFS log corruption Led 552,554, and 556-superblock corruption or custom ODM database corruption LED 553-/ etc/inittab file corruption

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