System Management PDF

System Management  Foreword  This chapter focuses on openEuler task, network, and process management, including scheduling. 2 Huawei Confidential  Objectives  Upon completion of this course, you will be familiar with:  One-off and scheduled task configur...

System Management  Foreword  This chapter focuses on openEuler task, network, and process management, including scheduling. 2 Huawei Confidential  Objectives  Upon completion of this course, you will be familiar with:  One-off and scheduled task configuration  openEuler network configuration, ensuring hosts can communicate  openEuler process viewing and management 3 Huawei Confidential  Contents 1. Task Management 2. Network Management 3. Process Management 4 Huawei Confidential What Is Task Management?  During system O&M, a specific task may need to be executed at a specific time.  For example, sending periodic emails or backing up and clearing log files.  The content of a task can be regarded as a series of commands, or a script, which needs to be executed at a specific time. 08:00 send email 15:00 reset log.txt... at, cron, anacron send-email.sh, reset.sh... 5 Huawei Confidential Task Management Types  at: scheduled task executed once, at a specified time.  cron: task executed periodically for multiple times. 6 Huawei Confidential Using the at Command for Scheduled Execution  The at command can be used to specify the time Linux will run scripts.  The atd process is the daemon process of at. It runs in the background when the system is started.  The atd process periodically checks the /var/spool/at directory to get the jobs written by running the at command. [root@openEuler ~]# systemctl status atd atd.service - Deferred execution scheduler Loaded: loaded (/usr/lib/systemd/system/atd.service; enabled; vendor preset: enabled) Active: active (running) since Wed 2020-07-08 11:20:10 CST; 2 weeks 6 days ago Docs: man:atd(8) Main PID: 2276 (atd) Tasks: 1 Memory: 2.1M CGroup: /system.slice/atd.service └─2276 /usr/sbin/atd -f Jul 08 11:20:10 localhost.localdomain systemd: Started Deferred execution scheduler. 7 Huawei Confidential at Command  The at command is used to schedule commands to be executed once only.  This command requires at least one command and one execution time.  The at command can specify only the time or both time and date.  at command syntax: at [-V] [-q queue] [-f file_name] [-mldbv] time at -c job [job...] 8 Huawei Confidential Setting an Absolute Time  The scheduled time can be written in any of the following formats:  hh:mm (hour:minute) on the current day. If the time has already passed, the job will be executed the following day.  midnight, noon, teatime (16:00)  12-hour time followed by am or pm  Time + date (month day, mm/dd/yy, or dd.mm.yy) 9 Huawei Confidential Setting a Relative Time  Relative timing is convenient for commands which need to be executed soon.  now+N minutes, hours, days, or weeks  N indicates the number of minutes, hours, days, or weeks. Another method is to use today and tomorrow to specify the time to complete commands.  Assume that the current time is 12:30 on June 7, 2015, and you want to run a command at 4:30 pm. at 4:30pm at now+240 minutes at 16:30 at 16:30 7.6.15 at 16:30 today at 16:30 6/7/15 at now+4 hours at 16:30 Jun 7  These eight commands all give the same result. 10 Huawei Confidential Execution Permission  The at command can only schedule commands from standard input or from the file specified by the -f option.  If user A switches to user B using the su command and then runs at, the at command's execution result will be sent to user B.  For other users, running a command or script depends on the /etc/at.allow and /etc/at.deny files. [root@openEuler ~]# at -f example.sh 15:00 warning: commands will be executed using /bin/sh job 1 at Wed Jul 29 15:00:00 2020 [root@openEuler ~]# atq 1 Wed Jul 29 15:00:00 2020 a root 11 Huawei Confidential Using the cron Command to Run Periodic Commands  The at command can run commands at a scheduled time, but only once.  If you need to run commands more than once, cron is a good helper. 12 Huawei Confidential Cron Running Mechanism  The cron service searches the /var/spool/cron directory for the crontab file named after the username in the /etc/passwd file, and then loads the crontab file into the memory.  It also searches for the /etc/crontab (timetable) file, which is written in a specific format.  If no crontab files are found, the cron service enters sleep mode and releases system resources. The cron service then wakes up every minute to check whether there are commands to be executed. 13 Huawei Confidential Crontab Command  The crontab command is used to install, edit, remove, and list crontab files.  Users can place the sequence of commands to be executed in crontab files. Each user can have their own crontab file.  Common crontab commands: crontab -u //Set a user's cron service. This option is required only when the crontab command is run by the root user. crontab -l //List details about a user's cron service. crontab -r //Remove a user's cron service. crontab -e //Edit a user's cron service. 14 Huawei Confidential Crontab Files  A crontab file contains a list of commands meant to be run at certain times.  Each crontab line has five time-and-date fields, followed by a command.  The fields are separated by spaces and tabs. The format is as follows: minute hour day-of-month month-of-year day-of-week commands 15 Huawei Confidential Crontab File Parameters minute hour day-of-month month-of-year day-of-week commands Parameter Description minute Minute (0–59) hour Hour (0–23) day-of-month Day of a month (1-31) month-of-year Month of a year (1-12) Day of a week (0–6). The value 0 indicates day-of-week Sunday. commands Commands to be executed For example, run a series of commands every Monday at 08:00 a.m. 00 08 * * 1 commands 16 Huawei Confidential Supplementary Description of Crontab File Parameters  The parameters on the previous slide cannot be left blank. They must be set.  An absolute path to the commands shall be provided.  In addition to numerical values, the following special symbols are allowed: Parameter Description * All numbers within the value range / Step value. For example, */5 indicates every five steps. - Value range , Several discrete numbers For example, add sleepy to the /tmp/test.txt file every two hours from 11:00 p.m. to 8:00 a.m. The corresponding line in the crontab file is as follows: * 23-8/2 * * * echo"sleepy" >> /tmp/test.txt 17 Huawei Confidential Editing the Configuration File  The cron service reads, every minute, /etc/crontab and all files in /var/spool/cron.  A crontab file contains user-specific commands. The /etc/crontab file contains system-wide commands.  The file format is as follows: SHELL=/bin/sh PATH=/usr/bin:/usr/sbin:/sbin:/bin:/usr/lib/news/bin MAILTO=root //If an error occurs or data is output, the data is sent to this account by email. HOME=/ # run-parts01 * * * * root run-parts /etc/cron.hourly // Execute the scripts in /etc/cron.hourly every hour. 02 4 * * * root run-parts /etc/cron.daily // Execute the scripts in /etc/cron.daily once a day. 22 4 * * 0 root run-parts /etc/cron.weekly // Execute the scripts in /etc/cron.weekly once a week. 42 4 1 * * root run-parts /etc/cron.monthly // Execute the scripts in /etc/cron.monthly once a month. 18 Huawei Confidential  Contents 1. Task Management 2. Network Management 3. Process Management 19 Huawei Confidential Important openEuler Network Concepts (1)  Device  NIC on the host  Broadcast address  Address used to send packets to all hosts on the network segment  Interface  Created by drivers on the devices so that the system can use the devices 20 Huawei Confidential Important openEuler Network Concepts (2)  Subnet mask  Number that distinguishes the network address and the host address within an IP address  Route  Next-hop IP address when IP packets are transmitted across network segments  Link  Device-to-network connection 21 Huawei Confidential Example of openEuler Device Information [root@openEuler ~]# ip addr // Check devices, including unconfigured network devices. 1: lo: mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: enp4s0: mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 28:6e:d4:89:70:de brd ff:ff:ff:ff:ff:ff inet 192.168.110.246/24 brd 192.168.110.255 scope global dynamic noprefixroute enp4s0 valid_lft 552233sec preferred_lft 552233sec inet6 fe80::fc7e:f7ba:e0d0:2f1f/64 scope link noprefixroute valid_lft forever preferred_lft forever 3: virbr0: mtu 1500 qdisc noqueue state DOWN group default qlen 1000 link/ether 52:54:00:c7:04:f6 brd ff:ff:ff:ff:ff:ff inet 192.168.122.1/24 brd 192.168.122.255 scope global virbr0 valid_lft forever preferred_lft forever 4: virbr0-nic: mtu 1500 qdisc fq_codel master virbr0 state DOWN group default qlen 1000 link/ether 52:54:00:c7:04:f6 brd ff:ff:ff:ff:ff:ff 22 Huawei Confidential Configuration File of the openEuler NIC  Default configuration path of network devices: /etc/sysconfig/network-scripts/  Configuration file: ifcfg-* [root@openEuler ~]# ls -l /etc/sysconfig/network-scripts/ total 4 -rw-r--r--. 1 root root 308 Jul 8 11:07 ifcfg-enp4s0 23 Huawei Confidential NIC Configuration File Parameters  Parameter values are case insensitive and quotation marks are not required. Parameter Description TYPE Interface type BOOTPROTO Boot-time protocol ONBOOT Whether to activate the device at boot-time IPADDR IP address NETMASK Subnet mask GATEWAY Gateway address BROADCAST Broadcast address MAC address. You only need to set one MAC address. MAC addresses HWADDR/MACADDR cannot conflict with each other. Whether to specify the DNS server address. If the DHCP protocol is PEERDNS used, the default value is yes. DNS{1, 2} DNS address USERCTL User permission control NAME Network connection name DEVICE Physical interface name 24 Huawei Confidential Modifying the Configuration File  Use an editor to modify the configuration file. Back up the file before modifying it.  Modification does not take effect immediately. For the modification to take effect, restart either the NetworkManager service process or the system. Back up the configuration file. [root@openEuler ~]# cp ifcfg-eth1 ifcfg-eth1.bak Restart the NetworkManager service process. [root@openEuler ~]# systemctl reload NetworkManager 25 Huawei Confidential Example of a Minimal NIC Configuration File  An available NIC configuration file does not need to list all configuration options. This configuration, for example, is valid: TYPE=Ethernet BOOTPROTO=static NAME=enp0s3 DEVICE=enp0s3 ONBOOT=yes IPADDR=192.168.56.100 NETMASK=255.255.255.0 26 Huawei Confidential Viewing the IP Address  Run the ip command to view device and address information. [root@openEuler ~]# ip addr show enp4s0 2: enp4s0: mtu 1500 qdisc fq_codel state UP group default qlen 1000 link/ether 28:6e:d4:89:70:de brd ff:ff:ff:ff:ff:ff inet 192.168.110.246/24 brd 192.168.110.255 scope global dynamic noprefixroute enp4s0 valid_lft 552070sec preferred_lft 552070sec inet6 fe80::fc7e:f7ba:e0d0:2f1f/64 scope link noprefixroute valid_lft forever preferred_lft forever No. Description Status of the current interface. UP: The current interface is enabled. DOWN: The current interface 1 is disabled. 2 Link information: MAC address of the device 3 inet information: IPv4 address and subnet mask 4 Broadcast address, scope, and device name 5 inet6 information: IPv6 information 27 Huawei Confidential Viewing Interface Statistics  Run the ip command to view network performance statistics.  RX indicates received data packet information.  TX indicates transmitted data packet information. [root@openEuler ~]# ip -s link show enp4s0 2: enp4s0: mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000 link/ether 28:6e:d4:89:70:de brd ff:ff:ff:ff:ff:ff RX: bytes packets errors dropped overrun mcast 20274318 204775 0 15 0 0 TX: bytes packets errors dropped carrier collsns 1057639 7024 0 0 0 0 28 Huawei Confidential Viewing Socket Information  Run the ss command to view socket statistics. You can add parameters to filter sockets of different types. For example, to view information about all TCP sockets, run the following command: [root@openEuler ~]# ss -ta State Recv-Q Send-Q Local Address:Port Peer Address:Port Process LISTEN 0 128 0.0.0.0:sunrpc 0.0.0.0:* LISTEN 0 32 192.168.122.1:domain 0.0.0.0:* LISTEN 0 128 0.0.0.0:ssh 0.0.0.0:* LISTEN 0 5 0.0.0.0:44321 0.0.0.0:* LISTEN 0 5 0.0.0.0:dey-sapi 0.0.0.0:* ESTAB 0 0 192.168.110.246:ssh 172.19.130.180:56950 LISTEN 0 128 [::]:sunrpc [::]:* LISTEN 0 128 [::]:ssh [::]:* LISTEN 0 5 [::]:44321 [::]:* LISTEN 0 5 [::]:dey-sapi [::]:* 29 Huawei Confidential NetworkManager  NetworkManager is a daemon process for dynamically controlling and configuring networks in the system. It is used to keep the current network devices and connections working.  The nmcli command line tool can be used to control NetworkManager. nmcli is comprehensive, powerful, and sophisticated.  Key concepts  Device: On a network, a device is a network interface.  Connection: A connection is a configuration used by a device.  A device may have multiple connections, but only one connection at a time can be active. 30 Huawei Confidential Viewing Network Information Using nmcli  con indicates a connection. The --active option can be used to filter active connections. [root@openEuler ~]# nmcli connection show --active NAME UUID TYPE DEVICE enp4s0 1d859d5a-b0c0-3b49-b153-269e0d4a85ce ethernet enp4s0 virbr0 52137c43-98c9-4f34-8954-d3d1ea89b946 bridge virbr0 31 Huawei Confidential Creating a Connection Using nmcli 1. Create a connection named Demo and connect it to the enp4s0 network port in DHCP mode. 2. Display all connections. [root@openEuler ~]# nmcli connection show --active NAME UUID TYPE DEVICE enp4s0 1d859d5a-b0c0-3b49-b153-269e0d4a85ce ethernet enp4s0 3. Start the created Demo connection. virbr0 52137c43-98c9-4f34-8954-d3d1ea89b946 bridge virbr0 [root@openEuler ~]# nmcli connection show NAME UUID TYPE DEVICE 4. Check the status of the connection. enp4s0 1d859d5a-b0c0-3b49-b153-269e0d4a85ce ethernet enp4s0 virbr0 52137c43-98c9-4f34-8954-d3d1ea89b946 bridge virbr0 [root@openEuler ~]# nmcli connection add con-name 'Demo' type Ethernet ifname enp4s0 Connection 'Demo' (789c723b-cd60-4515-99fc-5074b6f38498) successfully added. [root@openEuler ~]# nmcli connection show NAME UUID TYPE DEVICE enp4s0 1d859d5a-b0c0-3b49-b153-269e0d4a85ce ethernet enp4s0 virbr0 52137c43-98c9-4f34-8954-d3d1ea89b946 bridge virbr0 Demo 789c723b-cd60-4515-99fc-5074b6f38498 ethernet -- [root@openEuler ~]# nmcli connection up 'Demo' Connection successfully activated (D-Bus active path: /org/freedesktop/NetworkManager/ActiveConnection/16) [root@openEuler ~]# nmcli connection show NAME UUID TYPE DEVICE Demo 789c723b-cd60-4515-99fc-5074b6f38498 ethernet enp4s0 virbr0 52137c43-98c9-4f34-8954-d3d1ea89b946 bridge virbr0 enp4s0 1d859d5a-b0c0-3b49-b153-269e0d4a85ce ethernet -- 32 Huawei Confidential Modifying a Connection Using nmcli (1)  Run the nmcli con mod command to modify a connection. The input parameters are key-value pairs.  The key is the attribute name, which can be queried by running the nmcli con show [connection_name] command. For example: [root@openEuler ~]# nmcli connection show Demo connection.id: Demo connection.uuid: 789c723b-cd60-4515-99fc-5074b6f38498 connection.stable-id: -- connection.type: 802-3-ethernet connection.interface-name: enp4s0 connection.autoconnect: yes connection.autoconnect-priority: 0 connection.autoconnect-retries: -1 (default) connection.multi-connect: 0 (default) connection.auth-retries: -1 connection.timestamp: 1595988280 33 Huawei Confidential Modifying a Connection Using nmcli (2)  The following uses the domain name resolution (DNS) server as an example: [root@openEuler ~]# nmcli connection modify 'Demo' ipv4.dns 192.168.100.250 [root@openEuler ~]# nmcli connection show Demo | grep ipv4.dns ipv4.dns: 192.168.100.250 ipv4.dns-search: -- ipv4.dns-options: "" ipv4.dns-priority: 0 34 Huawei Confidential Routing  To enable two hosts in different subnets to communicate with each other, a mechanism is required to describe the traffic path between one host and another. This mechanism is called routing. Routing is described using routing entries.  A routing entry is a pair of predefined addresses: destination and gateway.  A routing entry allows communication with the destination to be completed through the gateway. Routing entries are listed in a routing table. 35 Huawei Confidential openEuler Route Management and Configuration  In openEuler, the route command is used to view, configure, and manage local routes.  Routes can also be managed using the ip and nmcli commands.  These commands modify the routing table of the system. When the system is started, the routing table is loaded into the memory and maintained by the kernel. 36 Huawei Confidential Using the route Command to View the Routing Table  Run the route command to view the routing table. [root@openEuler ~]# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.110.254 0.0.0.0 UG 100 0 0 enp4s0 192.168.110.0 0.0.0.0 255.255.255.0 U 100 0 0 enp4s0 192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0 37 Huawei Confidential Using the route Command to Add a Route  Add a temporary route to the network segment or host. route [-f] [-p] [Command [Destination] [mask Netmask] [Gateway] [metric Metric]] [if Interface]]  Example: [root@openEuler ~]# route add -net 192.168.101.0 netmask 255.255.255.0 dev enp4s0 [root@openEuler ~]# route add -host 192.168.100.10 dev enp4s0 [root@openEuler ~]# route Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface default _gateway 0.0.0.0 UG 100 0 0 enp4s0 192.168.100.10 0.0.0.0 255.255.255.255 UH 0 0 0 enp4s0 192.168.101.0 0.0.0.0 255.255.255.0 U 0 0 0 enp4s0 192.168.110.0 0.0.0.0 255.255.255.0 U 100 0 0 enp4s0 192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0 38 Huawei Confidential Using the route Command to Delete a Route  Run the route del command to delete a route to a network segment or host.  Syntax: route del [-net|-host] [netmask Nm] [gw Gw] [[dev] If]  Example: [root@openEuler ~]# route del -host 192.168.100.10 dev enp4s0 [root@openEuler ~]# route Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface default _gateway 0.0.0.0 UG 100 0 0 enp4s0 192.168.101.0 0.0.0.0 255.255.255.0 U 0 0 0 enp4s0 192.168.110.0 0.0.0.0 255.255.255.0 U 100 0 0 enp4s0 192.168.122.0 0.0.0.0 255.255.255.0 U 0 0 0 virbr0 39 Huawei Confidential Using the nmcli Command to Configure a Static Route  Run the nmcli command to configure a static route for a network connection. # nmcli connection modify enp3s0 +ipv4.routes "192.168.122.0/24 10.10.10.1"  Run the following interactive commands to configure a static route using the editor: # nmcli con edit type ethernet con-name enp3s0 ===| nmcli interactive connection editor |=== Adding a new '802-3-ethernet' connection Type 'help' or '?' for available commands. Type 'describe [.]' for detailed property description. You may edit the following settings: connection, 802-3-ethernet (ethernet), 802-1x, ipv4, ipv6, dcb nmcli> set ipv4.routes 192.168.122.0/24 10.10.10.1 nmcli> nmcli> save persistent Saving the connection with 'autoconnect=yes'. That might result in an immediate activation of the connection. Do you still want to save? [yes] yes Connection 'enp3s0' (1464ddb4-102a-4e79-874a-0a42e15cc3c0) successfully saved. nmcli> quit 40 Huawei Confidential Host Name  A host name uniquely identifies a device in a LAN.  The device can be a physical or a virtual machine.  The host name is stored in the /etc/hostname file. [root@openEuler ~]# cat /etc/hostname openEuler 41 Huawei Confidential Setting the Host Name  Run the hostname new-name command to temporarily set a host name (valid until next restart).  Setting a permanent host name: hostnamectl set-hostname new-name  Setting a host name by modifying the hostname file: write new-name to the /etc/hostname file. [root@openEuler ~]# hostname openEuler [root@openEuler ~]# hostname huawei [root@openEuler ~]# hostname huawei [root@openEuler ~]# hostnamectl set-hostname openEuler01 [root@openEuler ~]# hostname openEuler01 [root@openEuler ~]# echo "HCIA-openEuler" > /etc/hostname [root@openEuler ~]# hostname openEuler01 42 Huawei Confidential hosts File  Hosts in a LAN can be accessed through IP addresses.  When there are a large number of hosts in the LAN, IP addresses are difficult to remember. Therefore, we want to access hosts directly through their host names.  To do this, we can find the hosts we need in a table that records mappings between host names and IP addresses. This table is hosts. [root@openEuler ~]# cat /etc/hosts 127.0.0.1 localhost localhost.localdomain localhost4 localhost4.localdomain4 ::1 localhost localhost.localdomain localhost6 localhost4.localdomain6 43 Huawei Confidential Modifying the hosts File  You can use an editor to modify the hosts file in the following format: ipdomain.com 192.168.10.20 www.example.com  To delete an entry, add # to comment it out. For example: #ipdomain.com #192.168.10.20 www.example.com 44 Huawei Confidential Hosts and DNS  As the number of hosts on a network increases, it becomes difficult for a single hosts file to carry a large number of mappings.  If the IP address mapped to a domain name cannot be found in the hosts file, the host submits the domain name to the DNS server, after which the DNS server returns the IP address to the host. This process is called domain name resolution.  The DNS server is like a public hosts file or distributed database. 45 Huawei Confidential Querying a DNS Record (1)  In openEuler, run the nslookup command to query records on the DNS server.  You can run the nslookup command to check whether domain name resolution is normal and diagnose network problems.  The format of the nslookup command is as follows: nslookup domain [dns-server] In the preceding command, domain indicates the domain name to be queried. [dns-server] specifies the DNS server. This parameter is optional. Common values are 8.8.8.8 and 114.114.114.114. 46 Huawei Confidential Querying a DNS Record (2)  For example, to query the IP address mapped to exam.openEuler.com, run the following command: [root@openEuler ~]# nslookup exam.openEuler.com Server: 192.168.100.250 Address: 192.168.100.250#53 Name: exam.openEuler.com Address: 192.168.100.250 47 Huawei Confidential DNS Resolution Records  In addition to resolving a domain name to an IP address, the DNS server also supports other types of resolution records. Record Description A Maps a domain name to an IPv4 address. Maps one domain name to another domain name, to achieve the same domain access using both CNAME names. MX Sets up an email service that points to the email server address. NS Specifies a DNS server to resolve a subdomain name. TXT This parameter can be set to any value or left blank. Generally, it is used for verification. AAAA Maps a host name (or a domain name) to an IPv6 address. SRV Identifies computers hosting specific services. Indicates the start of authority. This record includes administrative information about its zone, SOA including the master server among multiple NS records. PTR Indicates the reverse of the A record, resolving an IP address to a domain name. Maps a domain name to an HTTP/HTTPS address. When a user accesses the domain name, the Explicit/Implicit URL user is automatically redirected to the target address. The real address is displayed in explicit forwarding forwarding and hidden in implicit forwarding. 48 Huawei Confidential Querying Other Records  Run the nslookup command to query various types of records. For example: [root@openEuler ~]# nslookup > set type=A > exam.openEuler.com Server: 192.168.100.250 Address: 192.168.100.250#53 Name: exam.openEuler.com Address: 192.168.100.250 49 Huawei Confidential  Contents 1. Task Management 2. Network Management 3. Process Management 50 Huawei Confidential Introduction to Processes  A process is an entity of a running program in a computer. It is a specific implementation of that program.  When a Linux process is created, the system allocates a segment of memory space (a certain logical address space) to the process. Stack Local variables High address ------------- ------------- Heap Dynamically requested memory area BSS segment Uninitialized static variables and global variables executable file Stored in the Low address Data Resident memory segment Initialized static variables and global variables Code segment Code area, including global constants (read-only) 51 Huawei Confidential Process Life Cycle  Each process has a unique process ID (PID), which is used for tracing the process.  Any process can create a child process by copying its own address space (fork). The parent process ID (PPID) is recorded in the child process.  The first system process is systemd, and all the other processes are its descendants. Parent wait( ) Parent process process fork( ) Child Child Child process process exec( ) process exit( ) Zombie state 52 Huawei Confidential Process State User running state running/0 System call or Return Interrupt, interrupt return interrupt Sleep Kernel Terminate Interruptible sleep state Zombie state running state interruptible/1 zombie/3 running/0 Stop Sleep Schedule Resume Uninterruptible sleep state Ready state Continue Stopped state uninterruptible/2 Resume running/0 stopped/4 53 Huawei Confidential Process Priority (1)  A process's CPU resource (time slice) allocation refers to the priority of that process.  Processes with a higher priority will be executed first.  Configuring the priority of a process can improve system performance in a multitasking Linux environment. [root@openEuler ~]# ps -l F S UID PID PPID C PRI NI ADDR SZ WCHAN TTY TIME CMD 0S 0 686110 686109 0 80 0 - 3383 do_wai pts/0 00:00:00 bash 0S 0 686217 686110 0 80 0 - 3386 do_wai pts/0 00:00:00 bash 0R 0 688767 686217 0 80 0 - 3399 - pts/0 00:00:00 ps 54 Huawei Confidential Process Priority (2)  PRI: process priority, indicating the sequence in which a program will be executed by the CPU. A smaller value indicates higher process priority.  NI: nice value, indicating a corrected process priority value. It can be understood as "concession".  The nice value of a process is not the priority of that process. You can, however, adjust the nice value to affect the priority value. Priority (PRI) Range Description High priority -20 nice 19 0—99 Real-time process Real-time Common 100—139 Non-real-time process 139 0 100 55 Huawei Confidential Adjusting the Priority of a Process  In openEuler, nice and renice are used to adjust the nice value of a process, which affects the process priority.  The syntax of the nice command is as follows (the adjustment value range is -19 to 20): nice [-n adjustment] [command [arg...]]  To set vi priority to -18, for example, run the following command: nice -n -18 vi &  The adjustment range of the renice command is the same as for nice. Objects include the program group -g, process -p, and user -u. The syntax is as follows: renice [-n adjustment] [-]  To set vi priority to -12, for example, run the following command: # renice -n 12 -p 9700 9700(process ID) old priority -18, new priority 12 56 Huawei Confidential Foreground and Background Processes  Background processes barely interact with users, so they do not need high priority.  A daemon process of Linux is a special background process that is independent of the terminal. It periodically executes tasks, or waits to resume executing tasks.  Foreground processes interact with users, requiring a high response speed and high priority.  A foreground process is a process used by a user to control a terminal. 57 Huawei Confidential Controlling Foreground and Background Processes  The following are common commands used in openEuler to manage processes, including starting, stopping, and switching between foreground and background:  &: Place an ampersand (&) at the end of a command to execute it in the background.  Ctrl+z: Moves a running foreground process to the background and suspends it.  Ctrl+c: Interrupts a running process.  jobs: Lists processes running in the background.  fg: Moves a background process to the foreground.  bg: Resumes a background process. 58 Huawei Confidential Viewing Processes  When troubleshooting the system, it is important to know the status of processes.  In openEuler, run the ps or top command to view the details of different processes. 59 Huawei Confidential Using the ps and top Commands to View Processes  Run the ps command to list currently running processes and their accompanying details. The table below describes the fields.  Run the ps aux or ps -ef command to view process information.  The ps command lists processes at a specific point in time. The top command shows processes in real time. Field Description UID User identifier PID Unique process identifier %CPU Process CPU usage %MEM Process memory usage NI Nice value (process concession) PRI Process priority TTY Terminal associated with the process STAT Process state 60 Huawei Confidential Using Signals to Manage Processes  In openEuler, processes communicate with each other through signals. The table below lists common signals.  A process signal is a predefined message that a process recognizes and chooses to act upon or ignore.  The system administrator needs to know what kind of signal to send to a process, and when. Signal Field Description 1 HUP Hangup 2 INT Terminal interrupt 3 QUIT Terminal quit 9 KILL Unconditional termination 11 SEGV Segment error 15 TERM Termination 17 STOP Stop executing unconditionally (but do not terminate) 18 TSTP Terminal stop (but continue to run in the background) 19 CONT Continue executing, if stopped (STOP or TSTP) 61 Huawei Confidential Managing Processes  In openEuler, the kill and killall commands send signals to processes.  To send signals to a process, the current user must be the owner of that process, or the root user.  kill PID can send a signal to a process. The TERM signal is sent by default. Use the –s option to specify other signals. For example: # kill 3389 # kill -s HUP 3389  killall process_name can send a signal to a process matching the specified process name. Supporting wildcard characters, killall can also send a signal to multiple processes. The following command, for example, will send a signal to all processes starting with 'python' # killall python* 62 Huawei Confidential  Quiz 1. (Single-answer) Which of the following commands can dynamically check host resource usage? A. ps B. top C. free D. lscpu 2. (True or false) The route command can view or configure host route information. Configured route information will remain valid permanently. A. True B. False 63 Huawei Confidential  Summary This chapter described common management operations in openEuler, including task, network, and process management.  Task management: how to schedule tasks in the system.  Network management: basic network knowledge and how to manage network elements in the system.  Process management: how to view and manage system processes. 64 Huawei Confidential Acronyms Acronym Full Name Description Portable Operating System Interface (POSIX) is the name of a family of related standards specified by the IEEE to define the application programming interface (API), along with POSIX Portable Operating System Interface shell and utilities interfaces for software compatible with variants of the Unix operating system, although the standard can apply to any operating system. GNU (prononunced GAH-noo with a hard "G") is an ambitious project started by Richard GNU GNU's Not Unix Stallman to create a completely free operating system based upon the design of Unix. AT&T American Telephone and Telegraph Co. It was an American telecommunications company founded in 1877 KDE K Desktop Environment One of the popular desktop environments for Linux. Kubuntu uses KDE by default. An interactive command interpreter and a command programming language. 2. A ksh Korn shell command interpreter developed for UNIX, which forms the basis for the z/OS shell. A command line processor for UNIX that provides interactive features such as job control csh C shell and command history. A visual computer environment that represents programs, files, and options with GUI graphical user interface graphical images, such as icons, menus, and dialog boxes, on the screen. A means of communication between a program and its user, based solely on textual CLI command-line interface input and output. 65 Huawei Confidential Thank you. 把数字世界带入每个人、每个家庭、 每个组织，构建万物互联的智能世界。 Bring digital to every person, home, and organization for a fully connected, intelligent world. 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