现象：
1. 系统启动时卡住。
2. 断电重启后，会出现如下界面：
welcome to emergency mode！
3. 系统/var/log/messages中显示如下：
Apr 9 11:36:21 inspur01 systemd-fsck: /dev/sda2: recovering journal Apr 9 11:36:21 inspur01 systemd-fsck: /dev/sda2: clean, 339/128016 files, 127461/512000 blocks Apr 9 11:36:21 inspur01 systemd: Started File System Check on /dev/disk/by-uuid/f5ddd083-a188-4e3b-9574-3b4dadf5bbfe. Apr 9 11:36:21 inspur01 systemd: Mounting /boot... Apr 9 11:36:21 inspur01 systemd-fsck: /dev/sda6 contains a file system with errors, check forced. Apr 9 11:36:21 inspur01 kernel: EXT4-fs (sda2): mounted filesystem with ordered data mode. Opts: (null) Apr 9 11:36:21 inspur01 systemd: Mounted /boot. Apr 9 11:36:21 inspur01 systemd: Mounting /boot/efi... Apr 9 11:36:21 inspur01 systemd: Mounted /boot/efi. Apr 9 11:36:21 inspur01 kernel: FAT-fs (sda8): Volume was not properly unmounted. Some data may be corrupt. Please run fsck. Apr 9 11:36:22 inspur01 systemd-fsck: /dev/sda6: Deleted inode 29 has zero dtime. FIXED. Apr 9 11:36:22 inspur01 systemd-fsck: /dev/sda6: Inodes that were part of a corrupted orphan linked list found. Apr 9 11:36:22 inspur01 systemd-fsck: /dev/sda6: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY. Apr 9 11:36:22 inspur01 systemd-fsck: (i.e., without -a or -p options) Apr 9 11:36:22 inspur01 systemd-fsck: fsck failed with error code 4. Apr 9 11:36:22 inspur01 systemd-fsck: Running request emergency.target/start/replace Apr 9 11:36:22 inspur01 systemd: Started File System Check on /dev/disk/by-uuid/d63bef64-e374-4239-bf7d-d37edcb6efc2. Apr 9 11:36:22 inspur01 systemd: Mounting /var/log... Apr 9 11:36:22 inspur01 systemd: Stopped Dump dmesg to /var/log/dmesg. Apr 9 11:36:22 inspur01 systemd: Stopped target Multi-User System.
解决方法：
1. 通过日志分析是磁盘sda的sda6分区出现文件系统error。
2.重启系统，进入单用户模式。步骤如下：
reboot--> 长按e ---> 将rhgb quiet替换成 single ---> ctrl + x进行重启。
3. 进入单用户模式后df显示如下
说明sda6是系统的日志分区。
4. 通过umount /var/log卸载挂载目录，并查看/dev/sda6分区，发现存在error。
5. 修复文件系统
fsck.ext4 -f /dev/sda6
并通过fsck.ext4 -a /dev/sda6进行查看
