现象描述：
一台机器挂载了两块数据盘(/dev/sdb,/dev/sdc)
[root@localhost ~]# df -h Filesystem Size Used Avail Use% Mounted on devtmpfs 189M 0 189M 0% /dev tmpfs 203M 0 203M 0% /dev/shm tmpfs 203M 628K 203M 1% /run tmpfs 203M 0 203M 0% /sys/fs/cgroup /dev/mapper/openeuler-root 17G 8.8G 7.0G 56% / tmpfs 203M 4.0K 203M 1% /tmp /dev/sda1 976M 120M 790M 14% /boot tmpfs 41M 0 41M 0% /run/user/989 tmpfs 41M 0 41M 0% /run/user/0 /dev/sdb 9.8G 37M 9.3G 1% /test /dev/sdc 9.8G 37M 9.3G 1% /test1 [root@localhost test1]# ll /test total 24K drwx------ 1 root root 4 Dec 5 17:13 nginx drwx------ 2 root root 4.0K Dec 5 17:13 data drwx------ 2 root root 16K Dec 5 16:35 lost+found [root@localhost test1]# ll /test1 total 24K drwx------ 1 root root 4 Dec 5 17:13 tomcat drwx------ 2 root root 4.0K Dec 5 17:13 data2 drwx------ 2 root root 16K Dec 5 16:36 lost+found [root@localhost ~]# tail -2 /etc/fstab /dev/sdb /test ext4 defaults 0 0 /dev/sdc /test1 ext4 defaults 0 0
由于挂载的sdb一直没有使用，数据都放在sdc下，所以操作将它删除，重启后发现机器要一分多钟才可以连接：查看message日志发现有timed out：
[root@localhost ~]# cat /var/log/messages |grep -C30 'Timed' Dec 5 17:19:59 localhost kernel: [ 56.571447] hv_balloon: Max. dynamic memory size: 1024 MB Dec 5 17:20:40 localhost systemd[1]: dev-sdc.device: Job dev-sdc.device/start timed out. Dec 5 17:20:40 localhost systemd[1]: Timed out waiting for device /dev/sdc. Dec 5 17:20:40 localhost systemd[1]: Dependency failed for /test1. Dec 5 17:20:40 localhost systemd[1]: Dependency failed for Local File Systems. Dec 5 17:20:40 localhost systemd[1]: local-fs.target: Job local-fs.target/start failed with result 'dependency'. Dec 5 17:20:40 localhost systemd[1]: local-fs.target: Triggering OnFailure= dependencies. Dec 5 17:20:40 localhost systemd[1]: local-fs.target: Failed to enqueue OnFailure= job, ignoring: Unit emergency.service has a bad unit file setting. Dec 5 17:20:40 localhost systemd[1]: test1.mount: Job test1.mount/start failed with result 'dependency'. Dec 5 17:20:40 localhost systemd[1]: dev-sdc.device: Job dev-sdc.device/start failed with result 'timeout'. Dec 5 17:20:40 localhost systemd[1]: Starting Restore /run/initramfs on shutdown... Dec 5 17:20:40 localhost systemd[1]: Condition check resulted in Rebuild Dynamic Linker Cache being skipped. Dec 5 17:20:40 localhost systemd[1]: Condition check resulted in Store a System Token in an EFI Variable being skipped. Dec 5 17:20:40 localhost systemd[1]: Condition check resulted in Rebuild Journal Catalog being skipped. Dec 5 17:20:40 localhost systemd[1]: Condition check resulted in Commit a transient machine-id on disk being skipped. Dec 5 17:20:40 localhost systemd[1]: Starting Create Volatile Files and Directories... Dec 5 17:20:40 localhost systemd[1]: Condition check resulted in Update is Completed being skipped.
可能原因：
近期除删除sdb磁盘外无其他操作，可能是删除磁盘导致的
定位思路：
查看磁盘数据和盘符是否正常：
[root@localhost ~]# df -h Filesystem Size Used Avail Use% Mounted on devtmpfs 189M 0 189M 0% /dev tmpfs 203M 0 203M 0% /dev/shm tmpfs 203M 632K 203M 1% /run tmpfs 203M 0 203M 0% /sys/fs/cgroup /dev/mapper/openeuler-root 17G 8.9G 7.0G 56% / tmpfs 203M 4.0K 203M 1% /tmp /dev/sdb 9.8G 37M 9.3G 1% /test /dev/sda1 976M 120M 790M 14% /boot tmpfs 41M 0 41M 0% /run/user/989 tmpfs 41M 0 41M 0% /run/user/0 [root@localhost ~]# ll /test total 24K drwx------ 1 root root 4 Dec 5 17:13 tomcat drwx------ 2 root root 4.0K Dec 5 17:13 data2 drwx------ 2 root root 16K Dec 5 16:36 lost+found
发现数据没有丢失，但磁盘名称和挂载目录由原来的sdc变成sdb,test1目录变成test目录
查看开机自启挂载方式：
[root@localhost ~]# tail -2 /etc/fstab /dev/sdb /test ext4 defaults 0 0 /dev/sdc /test1 ext4 defaults 0 0
确认fstab里挂载写的是磁盘名称，不是UUID形式，所以当删除无用数据盘sdb后，导致sdc顶替成为了sdb,而文件中本来的sdc由于识别不到，导致系统重启Timed out
解决方法：
查看磁盘对应的UUID，更换UUID方式挂载：
[root@localhost ~]# blkid /dev/mapper/openeuler-root: UUID="e45aaa82-334c-4460-a96d-e0f229e1019a" BLOCK_SIZE="4096" TYPE="ext4" /dev/sda2: UUID="VIRBUS-atLc-4Rd6-rsVk-0ZAO-1Gi3-zaCqgZ" TYPE="LVM2_member" PARTUUID="d944d5f4-02" /dev/mapper/openeuler-swap: UUID="3a2e33ca-eda1-473d-aa59-eed4e6e0d533" TYPE="swap" /dev/sdb: UUID="d7770de4-6932-413a-b3ab-5b4e0174dd59" BLOCK_SIZE="4096" TYPE="ext4" /dev/sda1: UUID="541688f6-935c-4ffa-b86b-2c062cbc6c08" BLOCK_SIZE="4096" TYPE="ext4" PARTUUID="d944d5f4-01" [root@localhost ~]# sed -i 's#/dev/sdb#UUID=d7770de4-6932-413a-b3ab-5b4e0174dd59#g' /etc/fstab [root@localhost ~]# tail -2 /etc/fstab UUID=d7770de4-6932-413a-b3ab-5b4e0174dd59 /test ext4 defaults 0 0 /dev/sdc /test1 ext4 defaults 0 0 之后删除/dev/sdc这行，因为他已经更名为了/dev/sdb
重启系统
无Timed out,搞定~！