dd if=/dev/zero 让驱动器内容保持不变? U 盘坏了?

dd if=/dev/zero 让驱动器内容保持不变? U 盘坏了?

我想我可以使用 来破坏驱动器的所有分区dd if=/dev/zero of=/dev/sdX。在过去,这一直对我有用,但在这种情况下,它没有按预期工作。

#check the partitions
➜  ~ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0   477G  0 disk 
├─sda1   8:1    0   512M  0 part /boot/efi
└─sda2   8:2    0 476.4G  0 part /
sdb      8:16   1  14.6G  0 disk 
├─sdb1   8:17   1   292M  0 part /media/james/Gentoo amd64 20190703T214502Z
└─sdb2   8:18   1   6.3M  0 part /media/james/GENTOOLIVE

#unmount and confirm the drive is still seen.

➜  ~ sudo umount "/media/james/Gentoo amd64 20190703T214502Z"
➜  ~ sudo umount "/media/james/GENTOOLIVE"
➜  ~ lsblk                                                   
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0   477G  0 disk 
├─sda1   8:1    0   512M  0 part /boot/efi
└─sda2   8:2    0 476.4G  0 part /
sdb      8:16   1  14.6G  0 disk 
├─sdb1   8:17   1   292M  0 part 
└─sdb2   8:18   1   6.3M  0 part 

#Run dd

➜  ~ sudo dd if=/dev/zero of=/dev/sdb bs=3M                  
dd: error writing '/dev/sdb': No space left on device
2649+0 records in
2648+0 records out
8330620928 bytes (8.3 GB, 7.8 GiB) copied, 5.50879 s, 1.5 GB/s

#the partitions are still there!

➜  ~ lsblk

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0   477G  0 disk 
├─sda1   8:1    0   512M  0 part /boot/efi
└─sda2   8:2    0 476.4G  0 part /
sdb      8:16   1  14.6G  0 disk 
├─sdb1   8:17   1   292M  0 part 
└─sdb2   8:18   1   6.3M  0 part 
➜  ~ lsblk

#after unplugging and replugging the drive, the old partition still mounts and still contains files. I was able to open several and read the contents.

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0   477G  0 disk 
├─sda1   8:1    0   512M  0 part /boot/efi
└─sda2   8:2    0 476.4G  0 part /
sdb      8:16   1  14.6G  0 disk 
├─sdb1   8:17   1   292M  0 part 
└─sdb2   8:18   1   6.3M  0 part /media/james/GENTOOLIVE

真正让我困惑的是,如果我查看 Gparted,设备显示为 8GB 未分配,但这是一个 16GB 驱动器。

我跑了badblocks -wsv,虽然过去了,但跑得很快(几分钟而不是几小时)。拔掉并重新插入后,驱动器显示为/dev/sdc,Gparted 看到名为“gentoo”的 14.56GB 分区

Testing with pattern 0xaa: set_o_direct: Invalid argument/0/0 errors)
done                                                 
Reading and comparing: done                                                 
Testing with pattern 0x55: done                                                 
Reading and comparing: done                                                 
Testing with pattern 0xff: done                                                 
Reading and comparing: done                                                 
Testing with pattern 0x00: done                                                 
Reading and comparing: done                                                 
Pass completed, 0 bad blocks found. (0/0/0 errors)
➜  ~ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0   477G  0 disk 
├─sda1   8:1    0   512M  0 part /boot/efi
└─sda2   8:2    0 476.4G  0 part /
sdc      8:32   1  14.6G  0 disk 
├─sdc1   8:33   1   292M  0 part 
└─sdc2   8:34   1   6.3M  0 part 

我猜我应该把这个闪存驱动器扔掉,但在我看来,这是一个奇怪的事件序列,我很好奇可能会导致什么样的故障(并不是真正寻找修复)。

编辑:这是在 Xubuntu 18.04 上

Edit2:重新启动后,归零按预期工作。我想这只是操作系统的暂时问题。我仍然很好奇到底是什么样的问题。

Edit3:我说得太早了,重启还不够。我以为dd可以正常工作,因为它需要正常的时间,但事实似乎并非如此。

➜  ~ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0   477G  0 disk 
├─sda1   8:1    0   512M  0 part /boot/efi
└─sda2   8:2    0 476.4G  0 part /
sdb      8:16   1  14.6G  0 disk 
├─sdb1   8:17   1   292M  0 part /media/james/Gentoo amd64 20190703T214502Z
└─sdb2   8:18   1   6.3M  0 part 
➜  ~ sudo dd if=/dev/zero of=/dev/sdb
[sudo] password for james: 
Sorry, try again.
[sudo] password for james: 
dd: writing to '/dev/sdb': No space left on device
30629377+0 records in
30629376+0 records out
15682240512 bytes (16 GB, 15 GiB) copied, 4232.1 s, 3.7 MB/s
➜  ~ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0   477G  0 disk 
├─sda1   8:1    0   512M  0 part /boot/efi
└─sda2   8:2    0 476.4G  0 part /
sdb      8:16   1  14.6G  0 disk 
├─sdb1   8:17   1   292M  0 part /media/james/Gentoo amd64 20190703T214502Z
└─sdb2   8:18   1   6.3M  0 part 

编辑4:好吧,dd确实有效,但 lsblk 直到我弹出并放回后才更新。

➜  ~ lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0   477G  0 disk 
├─sda1   8:1    0   512M  0 part /boot/efi
└─sda2   8:2    0 476.4G  0 part /
sdb      8:16   1  14.6G  0 disk 

编辑 5:我检查了 dmesg,有一条关于磁盘未正确安装的警告。

➜  ~ journalctl --dmesg --since="3 days ago" | grep sdb
Jul 09 19:59:27 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] 30595072 512-byte logical blocks: (15.7 GB/14.6 GiB)
Jul 09 19:59:27 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] Write Protect is off
Jul 09 19:59:27 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] Mode Sense: 43 00 00 00
Jul 09 19:59:27 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
Jul 09 19:59:27 james-Latitude-E7470 kernel:  sdb: sdb1
Jul 09 19:59:27 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] Attached SCSI removable disk
Jul 09 19:59:33 james-Latitude-E7470 kernel: FAT-fs (sdb1): Volume was not properly unmounted. Some data may be corrupt. Please run fsck.
Jul 10 02:38:38 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] 30629376 512-byte logical blocks: (15.7 GB/14.6 GiB)
Jul 10 02:38:38 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] Write Protect is off
Jul 10 02:38:38 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] Mode Sense: 43 00 00 00
Jul 10 02:38:38 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
Jul 10 02:38:38 james-Latitude-E7470 kernel:  sdb: sdb1 sdb2
Jul 10 02:38:38 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] Attached SCSI removable disk
Jul 10 04:12:42 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] 30629376 512-byte logical blocks: (15.7 GB/14.6 GiB)
Jul 10 04:12:42 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] Write Protect is off
Jul 10 04:12:42 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] Mode Sense: 43 00 00 00
Jul 10 04:12:42 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
Jul 10 04:12:42 james-Latitude-E7470 kernel: sd 3:0:0:0: [sdb] Attached SCSI removable disk

答案1

#the partitions are still there!

至少这部分还是正常的。您必须重新读取分区表来更新分区信息。您可以触发重读

blockdev --rereadpt /dev/sdx

(或者,sfdisk --re-read但该选项已从最新版本的 中删除sfdisk)。


对于其他一切,是的,基于闪存的存储可能会陷入只读模式。由于其他原因也可能会发生奇怪的事情,例如,如果 USB 连接不稳定,设备/dev/sdx可能会被丢弃,并重新检测为/dev/sdy所有写入/dev/sdx进入地狱状态,但我想这会在您的lsblk.

有时会出现有趣的错误消息dmesg,但总而言之...如果您的 USB 记忆棒出现故障,您只需要换一个新的,没有办法解决。


为了完整起见,这里还有这种特殊情况(用户错误):

# dd bs=1M if=/dev/zero of=/dev/sdx
dd: error writing '/dev/sdx': No space left on device
7956+0 records in
7955+0 records out
8341966848 bytes (8.3 GB, 7.8 GiB) copied, 2.08568 s, 4.0 GB/s

所以。该命令是否写入设备?

一点也不。我什至没有/dev/sdx。相反,它/dev用 50% RAM 大小的常规零文件填充了我的 tmpfs。 (我真的应该调整我的 tmpfs 大小限制。如果您在两个 tmpfs 实例上执行此操作,系统会因为 RAM 已满而崩溃。)

当设备完全丢失或设备名称输入错误时,就会发生这种情况,因为dd根本不会事先检查是否存在,并且如果您的计算机有大量 RAM,并且/dev不限于像 那样的合理大小10M,那么您会得到这个令人困惑的结果。

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