RHCSA-B1. 破解修改root密码

刺骨的言语ヽ痛彻心扉 2022-09-14 02:23 255阅读 0赞

# 红帽RHCE考试上午-RHCSA（RH134） #

## serverb.example.com 任务 ##

### 1. 改root密码 ###

*  第二部分的题如果破不了密码则进不去系统，则考试就挂了

#### 任务要求 ####

*  将serverb 的root 密码设置为123 。
 *  您需要获得系统访问权限才能进行此操作开机

#### 完成步骤 ####

1.  导航页面按e 键 -> linux 行尾加rd.break console=tty0 -> ctrl x
2.  `mount -o rw,remount /sysroot`
3.  `chroot /sysroot`
4.  `echo 123 | passwd --stdin root touch`
5.  `touch /.autorelabel`  
    `## 若系统之前开启了selinux，则必须执行该命令，否则将无法重启重置（这一步很关键！）`
6.  `sync`

### 考察的知识点： ###

#### mount 挂载 ####

*  救援模式中的根是假根，真根在/sysroot
 *  需要重新挂载上才能进行读写操作  
    `-o remount：将一个已经挂下的档案系统重新用不同的方式挂上。例如原先是唯读的系统，现在用可读写的模式重新挂上。`  
    `-o rw：用可读写模式挂上。`

#### touch /.autorelabel ####

*  .autorelabel 作用是让系统重新进行扫描所有文件。 当selinux关闭的时候，可以不建立该文件；但selinux开启时，必须建立！

#### sync ####

*  强制将内存中的文件缓冲写入磁盘，更新块信息。

#### CentOS 启动过程总结 ####

1.  POST
2.  boot loader centos7是grub2
3.  vmlinux(initramfs.img)
4.  roofs
5.  /sbin/init
6.  /etc/inittab 设置默认运行级别
7.  /etc/rc.d/rc.sysinit 运行系统初始脚本完成系统初始化
8.  /etc/rc\#.d/Sxxxx 启动需要启动服务关闭对应下需要关闭的服务
9.  /etc/rc.d/rc.local
10. 设置登录终端

#### CentOS 7之后版本引导顺序 ####

1.  UEFi或BIOS初始化，运行POST开机自检
2.  选择启动设备
3.  引导装载程序, centos7是grub2,加载装载程序的配置文件：

/etc/grub.d/
    /etc/default/grub
    /boot/grub2/grub.cfg

1.  加载initramfs驱动模块
2.  加载内核选项
3.  内核初始化，centos7使用systemd代替init
4.  执行initrd.target所有单元，包括挂载/etc/fstab
5.  从initramfs根文件系统切换到磁盘根目录
6.  systemd执行默认target配置，配置文件/etc/systemd/system/default.target
7.  systemd执行sysinit.target初始化系统及basic.target准备操作系统
8.  systemd启动multi-user.target下的本机与服务器服务
9.  systemd执行multi-user.target下的/etc/rc.d/rc.local
10. Systemd执行multi-user.target下的getty.target及登录服务
11. systemd执行graphical需要的服务

#### Linux的bootloader ####

*  LILO：LInux LOader，早期的bootloader，功能单一
 *  GRUB: GRand Unified Bootloader, CentOS 5,6 GRUB 0.97: GRUB Legacy， CentOS 7 以后使用GRUB 2.02

#### GRUB 启动阶段 ####

*  primary boot loader :  
    1st stage：MBR的前446个字节  
    1.5 stage：MBR 之后的扇区，让stage1中的bootloader能识别stage2所在的分区上的文件系统
 *  secondary boot loader ：2nd stage，分区文件/boot/grub/

#### GURB主要内容 ####

[root@C8-4-184-nfs ~]# ll /etc/grub.d/
    total 84
    -rwxr-xr-x. 1 root root  8958 Nov 26  2019 00_header
    -rwxr-xr-x. 1 root root  1043 Jun 27  2019 00_tuned
    -rwxr-xr-x. 1 root root  1240 Nov 26  2019 01_menu_auto_hide
    -rwxr-xr-x. 1 root root   232 Nov 26  2019 01_users
    -rwxr-xr-x. 1 root root 13434 Nov 26  2019 10_linux
    -rwxr-xr-x. 1 root root 11696 Nov 26  2019 20_linux_xen
    -rwxr-xr-x. 1 root root  2559 Nov 26  2019 20_ppc_terminfo
    -rwxr-xr-x. 1 root root 10670 Nov 26  2019 30_os-prober
    -rwxr-xr-x. 1 root root  1412 Nov 26  2019 30_uefi-firmware
    -rwxr-xr-x. 1 root root   214 Nov 26  2019 40_custom
    -rwxr-xr-x. 1 root root   216 Nov 26  2019 41_custom
    -rw-r--r--. 1 root root   483 Nov 26  2019 README
    [root@C8-4-184-nfs ~]# ll /etc/default/grub
    -rw-r--r-- 1 root root 350 May 20 06:28 /etc/default/grub
    [root@C8-4-184-nfs ~]# cat /etc/default/grub
    GRUB_TIMEOUT=5
    GRUB_DISTRIBUTOR="$(sed 's, release .*$,,g' /etc/system-release)"
    GRUB_DEFAULT=saved
    GRUB_DISABLE_SUBMENU=true
    GRUB_TERMINAL_OUTPUT="console"
    GRUB_CMDLINE_LINUX="net.ifnames=0 crashkernel=auto resume=UUID=b3fd1c68-6653-41ff-8ecb-25fdcfeeced9 rhgb quiet net.ifnames=0 net.ifnames=0"
    GRUB_DISABLE_RECOVERY="true"
    GRUB_ENABLE_BLSCFG=true
    [root@C8-4-184-nfs ~]# cat /etc/grub
    grub2.cfg  grub.d/    
    [root@C8-4-184-nfs ~]# cat /etc/grub2.cfg 
    #
    # DO NOT EDIT THIS FILE
    #
    # It is automatically generated by grub2-mkconfig using templates
    # from /etc/grub.d and settings from /etc/default/grub
    #
    
    ### BEGIN /etc/grub.d/00_header ###
    set pager=1
    
    if [ -f ${config_directory}/grubenv ]; then
      load_env -f ${config_directory}/grubenv
    elif [ -s $prefix/grubenv ]; then
      load_env
    fi
    if [ "${next_entry}" ] ; then
       set default="${next_entry}"
       set next_entry=
       save_env next_entry
       set boot_once=true
    else
       set default="${saved_entry}"
    fi
    
    if [ x"${feature_menuentry_id}" = xy ]; then
      menuentry_id_option="--id"
    else
      menuentry_id_option=""
    fi
    
    export menuentry_id_option
    
    if [ "${prev_saved_entry}" ]; then
      set saved_entry="${prev_saved_entry}"
      save_env saved_entry
      set prev_saved_entry=
      save_env prev_saved_entry
      set boot_once=true
    fi
    
    function savedefault { 
      if [ -z "${boot_once}" ]; then
        saved_entry="${chosen}"
        save_env saved_entry
      fi
    }
    
    function load_video { 
      if [ x$feature_all_video_module = xy ]; then
        insmod all_video
      else
        insmod efi_gop
        insmod efi_uga
        insmod ieee1275_fb
        insmod vbe
        insmod vga
        insmod video_bochs
        insmod video_cirrus
      fi
    }
    
    terminal_output console
    if [ x$feature_timeout_style = xy ] ; then
      set timeout_style=menu
      set timeout=5
    # Fallback normal timeout code in case the timeout_style feature is
    # unavailable.
    else
      set timeout=5
    fi
    ### END /etc/grub.d/00_header ###
    
    ### BEGIN /etc/grub.d/00_tuned ###
    set tuned_params=""
    set tuned_initrd=""
    ### END /etc/grub.d/00_tuned ###
    
    ### BEGIN /etc/grub.d/01_menu_auto_hide ###
    if [ "${boot_success}" = "1" -o "${boot_indeterminate}" = "1" ]; then
      set last_boot_ok=1
    else
      set last_boot_ok=0
    fi
    
    # Reset boot_indeterminate after a successful boot
    if [ "${boot_success}" = "1" ] ; then
      set boot_indeterminate=0
    # Avoid boot_indeterminate causing the menu to be hidden more then once
    elif [ "${boot_indeterminate}" = "1" ]; then
      set boot_indeterminate=2
    fi
    set boot_success=0
    save_env boot_success boot_indeterminate
    
    if [ x$feature_timeout_style = xy ] ; then
      if [ "${menu_show_once}" ]; then
        unset menu_show_once
        save_env menu_show_once
        set timeout_style=menu
        set timeout=60
      elif [ "${menu_auto_hide}" -a "${last_boot_ok}" = "1" ]; then
        set orig_timeout_style=${timeout_style}
        set orig_timeout=${timeout}
        if [ "${fastboot}" = "1" ]; then
          # timeout_style=menu + timeout=0 avoids the countdown code keypress check
          set timeout_style=menu
          set timeout=0
        else
          set timeout_style=hidden
          set timeout=1
        fi
      fi
    fi
    ### END /etc/grub.d/01_menu_auto_hide ###
    
    ### BEGIN /etc/grub.d/01_users ###
    if [ -f ${prefix}/user.cfg ]; then
      source ${prefix}/user.cfg
      if [ -n "${GRUB2_PASSWORD}" ]; then
        set superusers="root"
        export superusers
        password_pbkdf2 root ${GRUB2_PASSWORD}
      fi
    fi
    ### END /etc/grub.d/01_users ###
    
    ### BEGIN /etc/grub.d/10_linux ###
    insmod part_msdos
    insmod ext2
    set root='hd0,msdos1'
    if [ x$feature_platform_search_hint = xy ]; then
      search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 --hint='hd0,msdos1'  ea560777-7040-46e1-9931-633142400896
    else
      search --no-floppy --fs-uuid --set=root ea560777-7040-46e1-9931-633142400896
    fi
    insmod part_msdos
    insmod ext2
    set boot='hd0,msdos1'
    if [ x$feature_platform_search_hint = xy ]; then
      search --no-floppy --fs-uuid --set=boot --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 --hint='hd0,msdos1'  ea560777-7040-46e1-9931-633142400896
    else
      search --no-floppy --fs-uuid --set=boot ea560777-7040-46e1-9931-633142400896
    fi
    
    # This section was generated by a script. Do not modify the generated file - all changes
    # will be lost the next time file is regenerated. Instead edit the BootLoaderSpec files.
    #
    # The blscfg command parses the BootLoaderSpec files stored in /boot/loader/entries and
    # populates the boot menu. Please refer to the Boot Loader Specification documentation
    # for the files format: https://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/.
    
    set default_kernelopts="root=UUID=827b1562-fd3a-4e03-ad8b-f4c0b8def517 ro net.ifnames=0 crashkernel=auto resume=UUID=b3fd1c68-6653-41ff-8ecb-25fdcfeeced9 rhgb quiet net.ifnames=0 net.ifnames=0 "
    
    insmod blscfg
    blscfg
    ### END /etc/grub.d/10_linux ###
    
    ### BEGIN /etc/grub.d/20_linux_xen ###
    ### END /etc/grub.d/20_linux_xen ###
    
    ### BEGIN /etc/grub.d/20_ppc_terminfo ###
    ### END /etc/grub.d/20_ppc_terminfo ###
    
    ### BEGIN /etc/grub.d/30_os-prober ###
    ### END /etc/grub.d/30_os-prober ###
    
    ### BEGIN /etc/grub.d/30_uefi-firmware ###
    ### END /etc/grub.d/30_uefi-firmware ###
    
    ### BEGIN /etc/grub.d/40_custom ###
    # This file provides an easy way to add custom menu entries. Simply type the
    # menu entries you want to add after this comment. Be careful not to change
    # the 'exec tail' line above.
    ### END /etc/grub.d/40_custom ###
    
    ### BEGIN /etc/grub.d/41_custom ###
    if [ -f  ${config_directory}/custom.cfg ]; then
      source ${config_directory}/custom.cfg
    elif [ -z "${config_directory}" -a -f  $prefix/custom.cfg ]; then
      source $prefix/custom.cfg;
    fi
    ### END /etc/grub.d/41_custom ###
    [root@C8-4-184-nfs ~]# cat /boot/grub2/grub.cfg 
    #
    # DO NOT EDIT THIS FILE
    #
    # It is automatically generated by grub2-mkconfig using templates
    # from /etc/grub.d and settings from /etc/default/grub
    #
    
    ### BEGIN /etc/grub.d/00_header ###
    set pager=1
    
    if [ -f ${config_directory}/grubenv ]; then
      load_env -f ${config_directory}/grubenv
    elif [ -s $prefix/grubenv ]; then
      load_env
    fi
    if [ "${next_entry}" ] ; then
       set default="${next_entry}"
       set next_entry=
       save_env next_entry
       set boot_once=true
    else
       set default="${saved_entry}"
    fi
    
    if [ x"${feature_menuentry_id}" = xy ]; then
      menuentry_id_option="--id"
    else
      menuentry_id_option=""
    fi
    
    export menuentry_id_option
    
    if [ "${prev_saved_entry}" ]; then
      set saved_entry="${prev_saved_entry}"
      save_env saved_entry
      set prev_saved_entry=
      save_env prev_saved_entry
      set boot_once=true
    fi
    
    function savedefault { 
      if [ -z "${boot_once}" ]; then
        saved_entry="${chosen}"
        save_env saved_entry
      fi
    }
    
    function load_video { 
      if [ x$feature_all_video_module = xy ]; then
        insmod all_video
      else
        insmod efi_gop
        insmod efi_uga
        insmod ieee1275_fb
        insmod vbe
        insmod vga
        insmod video_bochs
        insmod video_cirrus
      fi
    }
    
    terminal_output console
    if [ x$feature_timeout_style = xy ] ; then
      set timeout_style=menu
      set timeout=5
    # Fallback normal timeout code in case the timeout_style feature is
    # unavailable.
    else
      set timeout=5
    fi
    ### END /etc/grub.d/00_header ###
    
    ### BEGIN /etc/grub.d/00_tuned ###
    set tuned_params=""
    set tuned_initrd=""
    ### END /etc/grub.d/00_tuned ###
    
    ### BEGIN /etc/grub.d/01_menu_auto_hide ###
    if [ "${boot_success}" = "1" -o "${boot_indeterminate}" = "1" ]; then
      set last_boot_ok=1
    else
      set last_boot_ok=0
    fi
    
    # Reset boot_indeterminate after a successful boot
    if [ "${boot_success}" = "1" ] ; then
      set boot_indeterminate=0
    # Avoid boot_indeterminate causing the menu to be hidden more then once
    elif [ "${boot_indeterminate}" = "1" ]; then
      set boot_indeterminate=2
    fi
    set boot_success=0
    save_env boot_success boot_indeterminate
    
    if [ x$feature_timeout_style = xy ] ; then
      if [ "${menu_show_once}" ]; then
        unset menu_show_once
        save_env menu_show_once
        set timeout_style=menu
        set timeout=60
      elif [ "${menu_auto_hide}" -a "${last_boot_ok}" = "1" ]; then
        set orig_timeout_style=${timeout_style}
        set orig_timeout=${timeout}
        if [ "${fastboot}" = "1" ]; then
          # timeout_style=menu + timeout=0 avoids the countdown code keypress check
          set timeout_style=menu
          set timeout=0
        else
          set timeout_style=hidden
          set timeout=1
        fi
      fi
    fi
    ### END /etc/grub.d/01_menu_auto_hide ###
    
    ### BEGIN /etc/grub.d/01_users ###
    if [ -f ${prefix}/user.cfg ]; then
      source ${prefix}/user.cfg
      if [ -n "${GRUB2_PASSWORD}" ]; then
        set superusers="root"
        export superusers
        password_pbkdf2 root ${GRUB2_PASSWORD}
      fi
    fi
    ### END /etc/grub.d/01_users ###
    
    ### BEGIN /etc/grub.d/10_linux ###
    insmod part_msdos
    insmod ext2
    set root='hd0,msdos1'
    if [ x$feature_platform_search_hint = xy ]; then
      search --no-floppy --fs-uuid --set=root --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 --hint='hd0,msdos1'  ea560777-7040-46e1-9931-633142400896
    else
      search --no-floppy --fs-uuid --set=root ea560777-7040-46e1-9931-633142400896
    fi
    insmod part_msdos
    insmod ext2
    set boot='hd0,msdos1'
    if [ x$feature_platform_search_hint = xy ]; then
      search --no-floppy --fs-uuid --set=boot --hint-bios=hd0,msdos1 --hint-efi=hd0,msdos1 --hint-baremetal=ahci0,msdos1 --hint='hd0,msdos1'  ea560777-7040-46e1-9931-633142400896
    else
      search --no-floppy --fs-uuid --set=boot ea560777-7040-46e1-9931-633142400896
    fi
    
    # This section was generated by a script. Do not modify the generated file - all changes
    # will be lost the next time file is regenerated. Instead edit the BootLoaderSpec files.
    #
    # The blscfg command parses the BootLoaderSpec files stored in /boot/loader/entries and
    # populates the boot menu. Please refer to the Boot Loader Specification documentation
    # for the files format: https://www.freedesktop.org/wiki/Specifications/BootLoaderSpec/.
    
    set default_kernelopts="root=UUID=827b1562-fd3a-4e03-ad8b-f4c0b8def517 ro net.ifnames=0 crashkernel=auto resume=UUID=b3fd1c68-6653-41ff-8ecb-25fdcfeeced9 rhgb quiet net.ifnames=0 net.ifnames=0 "
    
    insmod blscfg
    blscfg
    ### END /etc/grub.d/10_linux ###
    
    ### BEGIN /etc/grub.d/20_linux_xen ###
    ### END /etc/grub.d/20_linux_xen ###
    
    ### BEGIN /etc/grub.d/20_ppc_terminfo ###
    ### END /etc/grub.d/20_ppc_terminfo ###
    
    ### BEGIN /etc/grub.d/30_os-prober ###
    ### END /etc/grub.d/30_os-prober ###
    
    ### BEGIN /etc/grub.d/30_uefi-firmware ###
    ### END /etc/grub.d/30_uefi-firmware ###
    
    ### BEGIN /etc/grub.d/40_custom ###
    # This file provides an easy way to add custom menu entries. Simply type the
    # menu entries you want to add after this comment. Be careful not to change
    # the 'exec tail' line above.
    ### END /etc/grub.d/40_custom ###
    
    ### BEGIN /etc/grub.d/41_custom ###
    if [ -f  ${config_directory}/custom.cfg ]; then
      source ${config_directory}/custom.cfg
    elif [ -z "${config_directory}" -a -f  $prefix/custom.cfg ]; then
      source $prefix/custom.cfg;
    fi
    ### END /etc/grub.d/41_custom ###