红帽学习笔记[RHCSA] 第八课[Nice值、时间同步、RPM与Yum软件安装]

第八课

nice值

• 什么是nice值

给进程设置的优先级就是nice。nice的范围是-20~20。nice值越小占用的系统资源就越多，就是这个进程不nice。

• 如何查看nice值

# 使用top命令查看时 会有一列时NI 就是nice值
top - 14:01:36 up 9 min,  2 users,  load average: 0.08, 0.23, 0.18
Tasks: 494 total,   2 running, 492 sleeping,   0 stopped,   0 zombie
%Cpu(s): 16.7 us, 16.7 sy,  0.0 ni, 66.7 id,  0.0 wa,  0.0 hi,  0.0 si,  0.0 st

   PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                              
  3742 root      20   0  619884  18616  12072 R  60.4  1.0   0:00.85 gnome-terminal-                      
  3778 root      20   0  123924   1940   1152 R  60.4  0.1   0:00.43 top                                  
     1 root      20   0   53692   7660   2524 S   0.0  0.4   0:03.93 systemd                              
     2 root      20   0       0      0      0 S   0.0  0.0   0:00.07 kthreadd                             
     3 root      20   0       0      0      0 S   0.0  0.0   0:00.34 ksoftirqd/0                          
     5 root       0 -20       0      0      0 S   0.0  0.0   0:00.00 kworker/0:0H                         
     7 root      rt   0       0      0      0 S   0.0  0.0   0:00.66 migration/0     

• 设置nice值

# 执行4个 dd命令 一致在吃资源
PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                              
  3985 root      20   0  107920    624    532 R  95.6  0.0   0:14.21 dd if=/dev/zero of=/dev/null         
  3977 root      20   0  107920    624    532 R  93.7  0.0   0:15.64 dd if=/dev/zero of=/dev/null         
  3981 root      20   0  107920    620    532 R  86.4  0.0   0:14.18 dd if=/dev/zero of=/dev/null         
  3973 root      20   0  107920    624    532 R  84.4  0.0   0:16.26 dd if=/dev/zero of=/dev/null 
# renice 其那两个nice值为-20
renice -19 3977
renice -20 3985
renice +19 3981
renice +19 3973
#再次查看top
   PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND                              
  3977 root       1 -19  107920    624    532 R 100.0  0.0  10:14.42 dd if=/dev/zero of=/dev/null         
  3985 root       0 -20  107920    624    532 R 100.0  0.0  10:38.96 dd if=/dev/zero of=/dev/null         
  3981 root      39  19  107920    620    532 R  96.5  0.0  10:01.17 dd if=/dev/zero of=/dev/null         
  3973 root      39  19  107920    624    532 R  88.6  0.0   9:55.61 dd if=/dev/zero of=/dev/null   
# 修改后-20的进程一直比19nice值得占用的多，此时如果再开一个进程会更明显，但是虚拟机卡住了，做不了任何操作

调整时间

• timedatectl

# 查看
[root@master /]# timedatectl
      Local time: Fri 2019-08-30 14:21:58 CST
  Universal time: Fri 2019-08-30 06:21:58 UTC
        RTC time: Fri 2019-08-30 14:21:58
        Timezone: Asia/Shanghai (CST, +0800)
     NTP enabled: yes
NTP synchronized: no
 RTC in local TZ: no
      DST active: n/a
# 设置时间
[root@master /]# timedatectl set-time "2019-08-30 14:24:20"
[root@master /]# date
Fri Aug 30 14:24:23 CST 2019
# 查看所有时区
[root@master /]# timedatectl list-timezones 
# 设置时区
[root@master /]# timedatectl set-timezone Asia/Hong_Kong
# 设置ntp同步为yes
timedatectl set-ntp 1

• 自动对时

使用的时服务 chronyd。redhat7自带的。

# 编辑配置文件，注释掉默认的4行，增加阿里云的同步时间配置
[root@master ~]# vi /etc/chrony.conf 
#server 0.rhel.pool.ntp.org iburst
#server 1.rhel.pool.ntp.org iburst
#server 2.rhel.pool.ntp.org iburst
#server 3.rhel.pool.ntp.org iburst
server ntp6.aliyun.com iburst
[root@localhost ~]# vi /etc/chrony.conf 
[root@localhost ~]# vi /etc/chrony.conf 
[root@localhost ~]# systemctl restart chronyd
[root@localhost ~]# systemctl enable chronyd

安装软件包

• 什么时RPM：RPM package manager 包管理

• 包的全名：

httpd-tools-2.4.6-17.el7.x86_64.rpm
# httpd-tools是名字
# 2.4.6是版本
# 17是发行班号（发行的次数）
# .el7是radhat7平台
# .x86_64处理器cpu的架构
# .noarch是32位64位都可以

• 考试提供的iso镜像中有rpm的包。挂载后直接使用

[root@localhost /]# mount /dev/sr0 /mnt
mount: /dev/sr0 is write-protected, mounting read-only
[root@localhost /]# cd /mnt/Packages/
# packages下面全都是rpm包 
	# -i 安装 -v详细信息 -h 显示进度条
[root@localhost Packages]#  rpm -ivh tree-1.6.0-10.el7.x86_64.rpm 
warning: tree-1.6.0-10.el7.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID fd431d51: NOKEY
Preparing...                          ################################# [100%]
Updating / installing...
   1:tree-1.6.0-10.el7                ################################# [100%]
# 卸载
[root@localhost Packages]# rpm -evh tree
Preparing...                          ################################# [100%]
Cleaning up / removing...
   1:tree-1.6.0-10.el7                ################################# [100%]
# 查看包
[root@localhost Packages]# rpm -q tree
tree-1.6.0-10.el7.x86_64
#查看所有包，太多了不直接显示
[root@localhost Packages]# rpm -qa|grep "tree"
tree-1.6.0-10.el7.x86_64
# 查看包的详细
[root@localhost Packages]# rpm -qi tree
Name        : tree
Version     : 1.6.0
Release     : 10.el7
Architecture: x86_64
Install Date: Fri 30 Aug 2019 04:16:26 PM CST
Group       : Applications/File
Size        : 89505
License     : GPLv2+
Signature   : RSA/SHA256, Thu 03 Apr 2014 05:33:48 AM CST, Key ID 199e2f91fd431d51
Source RPM  : tree-1.6.0-10.el7.src.rpm
Build Date  : Tue 28 Jan 2014 01:29:58 AM CST
Build Host  : x86-020.build.eng.bos.redhat.com
Relocations : (not relocatable)
Packager    : Red Hat, Inc. <http://bugzilla.redhat.com/bugzilla>
Vendor      : Red Hat, Inc.
URL         : http://mama.indstate.edu/users/ice/tree/
Summary     : File system tree viewer
Description :
The tree utility recursively displays the contents of directories in a
tree-like format.  Tree is basically a UNIX port of the DOS tree
utility.
# 查看包装在哪里
[root@localhost Packages]# rpm -ql tree
/usr/bin/tree
/usr/share/doc/tree-1.6.0
/usr/share/doc/tree-1.6.0/LICENSE
/usr/share/doc/tree-1.6.0/README
/usr/share/man/man1/tree.1.gz
# 查看文件从哪个包来的
[root@localhost Packages]# rpm -qf /usr/share/doc/tree-1.6.0
tree-1.6.0-10.el7.x86_64

• 关于rpm 包的依赖问题

  • 树形依赖: a->b->c直接按照提示从下层一个个装就可以，按照c>b>a的顺序

  • 环形依赖：a->b->c->a将三个包名写在一起，直接一次装

  • 模块依赖：用httpd举例

# 需要一些模块
[root@localhost Packages]# rpm -ivh httpd-2.4.6-17.el7.x86_64.rpm 
warning: httpd-2.4.6-17.el7.x86_64.rpm: Header V3 RSA/SHA256 Signature, key ID fd431d51: NOKEY
error: Failed dependencies:
	/etc/mime.types is needed by httpd-2.4.6-17.el7.x86_64
	httpd-tools = 2.4.6-17.el7 is needed by httpd-2.4.6-17.el7.x86_64
	libapr-1.so.0()(64bit) is needed by httpd-2.4.6-17.el7.x86_64
	libaprutil-1.so.0()(64bit) is needed by httpd-2.4.6-17.el7.x86_64
# 访问 http://www.rpmfind.net/ 去查找这个模块在哪个包中，安装那个包

使用yum 安装软件包

• 什么是yum ： yellow dog update manage黄狗更新管理器

• 使用rpm安装yum

[root@master Packages]# rpm -ivh yum-3.4.3-118.el7.noarch.rpm 
warning: yum-3.4.3-118.el7.noarch.rpm: Header V3 RSA/SHA256 Signature, key ID fd431d51: NOKEY
Preparing...                          ################################# [100%]
	package yum-3.4.3-118.el7.noarch is already installed

• 配置yum源

###注：考试给一个http的连接给啥写啥###
# 将iso光盘挂在到/mnt目录上
sudo mount -o /dev/sr0 /mnt
# 查看目录挂载
[kane@master mnt]$ df -H
Filesystem             Size  Used Avail Use% Mounted on
/dev/mapper/rhel-root   19G  3.3G   16G  18% /
devtmpfs               949M     0  949M   0% /dev
tmpfs                  958M  152k  958M   1% /dev/shm
tmpfs                  958M  9.4M  949M   1% /run
tmpfs                  958M     0  958M   0% /sys/fs/cgroup
/dev/sda1              521M  125M  397M  24% /boot
/dev/sr0               3.8G  3.8G     0 100% /mnt
# 我们将iso中的package配置成yum源
sudo yum-config-manager --add-repo=file:///mnt
# 到 yum源目录下
[root@master request-key.d]# cd /etc/yum.repos.d/
# 追加内容gpgcheck=0。让其不检查
[root@master yum.repos.d]# echo "gpgcheck=0" >> ./mnt.repo
# 刷新缓存
[root@master yum.repos.d]# yum makechahe

• 安装与安装回滚

# 安装httpd
[root@master yum.repos.d]# yum install httpd
# 查看安装历史
[root@master yum.repos.d]# yum history
Loaded plugins: langpacks, product-id, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
ID     | Login user               | Date and time    | Action(s)      | Altered
-------------------------------------------------------------------------------
     5 | kane <kane>              | 2019-10-22 13:45 | Install        |    5      
history list
# 回滚某次安装 使用ID
[root@master yum.repos.d]# yum history undo 5
# 再次查看，会多一个抹去的操作
[root@master yum.repos.d]# yum history
Loaded plugins: langpacks, product-id, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
ID     | Login user               | Date and time    | Action(s)      | Altered
-------------------------------------------------------------------------------
     6 | kane <kane>              | 2019-10-22 13:47 | Erase          |    5   
     5 | kane <kane>              | 2019-10-22 13:45 | Install        |    5    
history list
# 此处看不到每个Id都是做什么的，我们可以查看yum安装log
[root@master yum.repos.d]# cat /var/log/yum.log
Oct 22 13:45:09 Installed: apr-1.4.8-3.el7.x86_64
Oct 22 13:45:09 Installed: apr-util-1.5.2-6.el7.x86_64
Oct 22 13:45:09 Installed: httpd-tools-2.4.6-17.el7.x86_64
Oct 22 13:45:09 Installed: mailcap-2.1.41-2.el7.noarch
Oct 22 13:45:11 Installed: httpd-2.4.6-17.el7.x86_64
Oct 22 13:47:04 Erased: httpd-2.4.6-17.el7.x86_64
Oct 22 13:47:04 Erased: httpd-tools-2.4.6-17.el7.x86_64
Oct 22 13:47:04 Erased: mailcap-2.1.41-2.el7.noarch
Oct 22 13:47:04 Erased: apr-util-1.5.2-6.el7.x86_64
Oct 22 13:47:05 Erased: apr-1.4.8-3.el7.x86_64

• 软件包组

[root@master yum.repos.d]# yum groups list
Loaded plugins: langpacks, product-id, subscription-manager
This system is not registered to Red Hat Subscription Management. You can use subscription-manager to register.
There is no installed groups file.
Maybe run: yum groups mark convert (see man yum)
Available environment groups:
   Minimal Install
   Infrastructure Server
   File and Print Server
   Basic Web Server
   Virtualization Host
   Server with GUI
Available Groups:
   Compatibility Libraries
   Console Internet Tools
   Development Tools
   Graphical Administration Tools
   Legacy UNIX Compatibility
   Scientific Support
   Security Tools
   Smart Card Support
   System Administration Tools
   System Management
Done