在很多情况下，我们将U盘插入Linux系统之后，通过fdisk 进行磁盘的查看发现，并不是每次显示的设备名都一致，比如每次都是sdb，很有可能下次是sdc,sdd,这个跟你在插入U盘之前，系统是否插入存储有关，平时这个问题可能不会有什么影响，但是在ISCSI共享存储中，我们需要将外接存储一直挂载，并且经常进行操作，比如我们挂接了192.168.3.1上面的存储到本地，磁盘显示为：/dev/sdb,我们进行分区，格式化，将/dev/sdb1 挂载到  /test1目录下，我们需要经常对/test1进行读写操作，但是某次开机发现test1目录并没有挂载/dev/sdb1，为何？这就是共享存储在本地显示的设备名已经不再是sdb了，所以为了解决这样的情况，我们使用 UDEV进行设备管理，关于何为UDEV：百度知道如是说：

还是从ISCSI 的Target端跟Initiator端说起

Target端：ParaSec01 192.168.1.90

1.创建分区设备

[root@ParaSec01 ~]# hostnameParaSec01[root@ParaSec01 ~]# fdisk /dev/sda -lDisk /dev/sda (Sun disk label): 255 heads, 63 sectors, 3649 cylindersUnits = cylinders of 16065 * 512 bytes   Device Flag    Start       End    Blocks   Id  System[root@ParaSec01 ~]# cat | fdisk /dev/sda   << EOF> n> p> 1>> +2GB> w> EOFCommand (m for help): Partition number (1-8): Partition number (1-8): First cylinder (0-3649): Last cylinder or +size or +sizeM or +sizeK (0-3649, default 3649):Command (m for help): The partition table has been altered!Calling ioctl() to re-read partition table.WARNING: Re-reading the partition table failed with error 16: Device or resource busy.The kernel still uses the old table. The new table will be used atthe next reboot or after you run partprobe(8) or kpartx(8)Syncing disks.[root@ParaSec01 ~]# fdisk /dev/sda -lDisk /dev/sda (Sun disk label): 255 heads, 63 sectors, 3649 cylindersUnits = cylinders of 16065 * 512 bytes   Device Flag    Start       End    Blocks   Id  System/dev/sda1             0       243   1951897+  83  Linux native

2.编辑配置文件/etc/tgt/targets.conf，添加

    
         backing-store /dev/sda1
    

3.启动tgtd服务

[root@ParaSec01 ~]# service tgtd startStarting SCSI target daemon:                               [  OK  ][root@ParaSec01 ~]# tgt-admin  --showTarget 1: iqn.2013-05.com.clovem:target1    System information:        Driver: iscsi        State: ready    I_T nexus information:    LUN information:        LUN: 0            Type: controller            SCSI ID: IET     00010000            SCSI SN: beaf10            Size: 0 MB, Block size: 1            Online: Yes            Removable media: No            Prevent removal: No            Readonly: No            Backing store type: null            Backing store path: None            Backing store flags:        LUN: 1            Type: disk            SCSI ID: IET     00010001            SCSI SN: beaf11            Size: 2007 MB, Block size: 512            Online: Yes            Removable media: No            Prevent removal: No            Readonly: No            Backing store type: rdwr            Backing store path: /dev/sda1            Backing store flags:    Account information:    ACL information:        ALL

Initiator:hyperStor  192.168.3.30

[root@hyperStor ~]# hostnamehyperStor[root@hyperStor ~]# ls /dev/sd* -lbrw-rw----. 1 root disk 8,  0 Apr 25 23:46 /dev/sdabrw-rw----. 1 root disk 8,  1 Apr 25 23:46 /dev/sda1brw-rw----. 1 root disk 8,  2 Apr 25 23:46 /dev/sda2brw-rw----. 1 root disk 8,  3 Apr 25 23:46 /dev/sda3brw-rw----. 1 root disk 8, 16 May 10 10:55 /dev/sdbbrw-rw----. 1 root disk 8, 17 Apr 25 23:46 /dev/sdb1brw-rw----. 1 root disk 8, 18 Apr 25 23:46 /dev/sdb2brw-rw----. 1 root disk 8, 21 Apr 25 23:46 /dev/sdb5brw-rw----. 1 root disk 8, 22 Apr 25 23:46 /dev/sdb6brw-rw----. 1 root disk 8, 23 Apr 25 23:46 /dev/sdb7brw-rw----. 1 root disk 8, 24 May 13 09:37 /dev/sdb8[root@hyperStor ~]# iscsiadm  -m discovery -t sendtargets -p 192.168.1.90Starting iscsid:                                           [  OK  ]192.168.1.90:3260,1 iqn.2013-05.com.clovem:target1[root@hyperStor ~]# iscsiadm  -m node -T iqn.2013-05.com.clovem:target1 -lLogging in to [iface: default, target: iqn.2013-05.com.clovem:target1, portal: 192.168.1.90,3260] (multiple)Login to [iface: default, target: iqn.2013-05.com.clovem:target1, portal: 192.168.1.90,3260] successful.[root@hyperStor ~]# ls /dev/sd* -lbrw-rw----. 1 root disk 8,  0 Apr 25 23:46 /dev/sdabrw-rw----. 1 root disk 8,  1 Apr 25 23:46 /dev/sda1brw-rw----. 1 root disk 8,  2 Apr 25 23:46 /dev/sda2brw-rw----. 1 root disk 8,  3 Apr 25 23:46 /dev/sda3brw-rw----. 1 root disk 8, 16 May 10 10:55 /dev/sdbbrw-rw----. 1 root disk 8, 17 Apr 25 23:46 /dev/sdb1brw-rw----. 1 root disk 8, 18 Apr 25 23:46 /dev/sdb2brw-rw----. 1 root disk 8, 21 Apr 25 23:46 /dev/sdb5brw-rw----. 1 root disk 8, 22 Apr 25 23:46 /dev/sdb6brw-rw----. 1 root disk 8, 23 Apr 25 23:46 /dev/sdb7brw-rw----. 1 root disk 8, 24 May 13 09:37 /dev/sdb8brw-rw----. 1 root disk 8, 32 May 13 10:01 /dev/sdc

[root@hyperStor ~]# udevadm  monitormonitor will print the received events for:UDEV - the event which udev sends out after rule processingKERNEL - the kernel ueventKERNEL[1368410441.394299] add      /module/iscsi_tcp (module)KERNEL[1368410441.394360] add      /devices/virtual/iscsi_transport/tcp (iscsi_transport)KERNEL[1368410441.399931] add      /module/ib_addr (module)UDEV  [1368410441.403255] add      /module/iscsi_tcp (module)UDEV  [1368410441.403488] add      /devices/virtual/iscsi_transport/tcp (iscsi_transport)UDEV  [1368410441.404113] add      /module/ib_addr (module)KERNEL[1368410441.438772] add      /module/ib_core (module)UDEV  [1368410441.439227] add      /module/ib_core (module)KERNEL[1368410441.439564] add      /class/infiniband (class)UDEV  [1368410441.440168] add      /class/infiniband (class)KERNEL[1368410441.455582] add      /module/ib_mad (module)UDEV  [1368410441.456116] add      /module/ib_mad (module)KERNEL[1368410441.471202] add      /module/ib_sa (module)UDEV  [1368410441.471775] add      /module/ib_sa (module)KERNEL[1368410441.480950] add      /module/iw_cm (module)UDEV  [1368410441.481503] add      /module/iw_cm (module)KERNEL[1368410441.500212] add      /module/ib_cm (module)KERNEL[1368410441.500412] add      /class/infiniband_cm (class)UDEV  [1368410441.500802] add      /module/ib_cm (module)UDEV  [1368410441.500877] add      /class/infiniband_cm (class)KERNEL[1368410441.526953] add      /module/rdma_cm (module)UDEV  [1368410441.527567] add      /module/rdma_cm (module)KERNEL[1368410441.546686] add      /module/ib_iser (module)KERNEL[1368410441.546958] add      /devices/virtual/iscsi_transport/iser (iscsi_transport)UDEV  [1368410441.547237] add      /module/ib_iser (module)UDEV  [1368410441.547530] add      /devices/virtual/iscsi_transport/iser (iscsi_transport)KERNEL[1368410441.572754] add      /module/cxgb3i (module)KERNEL[1368410441.572918] add      /devices/virtual/iscsi_transport/cxgb3i (iscsi_transport)UDEV  [1368410441.573341] add      /module/cxgb3i (module)UDEV  [1368410441.573376] add      /devices/virtual/iscsi_transport/cxgb3i (iscsi_transport)KERNEL[1368410441.598469] add      /module/cxgb4i (module)KERNEL[1368410441.598592] add      /devices/virtual/iscsi_transport/cxgb4i (iscsi_transport)UDEV  [1368410441.598984] add      /module/cxgb4i (module)UDEV  [1368410441.599109] add      /devices/virtual/iscsi_transport/cxgb4i (iscsi_transport)KERNEL[1368410441.614902] add      /module/cnic (module)UDEV  [1368410441.615642] add      /module/cnic (module)KERNEL[1368410441.616337] add      /class/uio (class)UDEV  [1368410441.616888] add      /class/uio (class)KERNEL[1368410441.622577] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.0/uio/uio0 (uio)KERNEL[1368410441.625568] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.1/uio/uio1 (uio)KERNEL[1368410441.628628] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.0/uio/uio2 (uio)KERNEL[1368410441.631882] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.1/uio/uio3 (uio)KERNEL[1368410441.651946] add      /module/bnx2i (module)KERNEL[1368410441.652135] add      /devices/virtual/iscsi_transport/bnx2i (iscsi_transport)KERNEL[1368410441.652626] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.1/host9 (scsi)KERNEL[1368410441.652756] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.1/host9/scsi_host/host9 (scsi_host)KERNEL[1368410441.652935] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.1/host9/iscsi_host/host9 (iscsi_host)UDEV  [1368410441.653566] add      /module/bnx2i (module)UDEV  [1368410441.654118] add      /devices/virtual/iscsi_transport/bnx2i (iscsi_transport)KERNEL[1368410441.654909] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.0/host10 (scsi)UDEV  [1368410441.655058] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.1/host9 (scsi)KERNEL[1368410441.655165] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.0/host10/scsi_host/host10 (scsi_host)UDEV  [1368410441.655857] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.0/host10 (scsi)UDEV  [1368410441.657690] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.0/host10/scsi_host/host10 (scsi_host)KERNEL[1368410441.664302] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.0/host10/iscsi_host/host10 (iscsi_host)UDEV  [1368410441.664750] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.1/uio/uio3 (uio)UDEV  [1368410441.664962] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.0/uio/uio2 (uio)UDEV  [1368410441.665354] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.0/host10/iscsi_host/host10 (iscsi_host)UDEV  [1368410441.665613] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.1/host9/scsi_host/host9 (scsi_host)UDEV  [1368410441.665895] add      /devices/pci0000:00/0000:00:06.0/0000:05:00.1/host9/iscsi_host/host9 (iscsi_host)UDEV  [1368410441.666201] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.0/uio/uio0 (uio)UDEV  [1368410441.666256] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.1/uio/uio1 (uio)KERNEL[1368410441.666721] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.1/host11 (scsi)KERNEL[1368410441.666991] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.1/host11/scsi_host/host11 (scsi_host)KERNEL[1368410441.667305] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.1/host11/iscsi_host/host11 (iscsi_host)UDEV  [1368410441.667432] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.1/host11 (scsi)UDEV  [1368410441.668033] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.1/host11/iscsi_host/host11 (iscsi_host)UDEV  [1368410441.668233] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.1/host11/scsi_host/host11 (scsi_host)KERNEL[1368410441.668691] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.0/host12 (scsi)KERNEL[1368410441.668811] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.0/host12/scsi_host/host12 (scsi_host)KERNEL[1368410441.668996] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.0/host12/iscsi_host/host12 (iscsi_host)UDEV  [1368410441.669223] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.0/host12 (scsi)UDEV  [1368410441.670053] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.0/host12/scsi_host/host12 (scsi_host)UDEV  [1368410441.670093] add      /devices/pci0000:00/0000:00:04.0/0000:04:00.0/host12/iscsi_host/host12 (iscsi_host)KERNEL[1368410483.991398] add      /devices/platform/host13 (scsi)KERNEL[1368410483.991455] add      /devices/platform/host13/scsi_host/host13 (scsi_host)KERNEL[1368410483.992838] add      /devices/platform/host13/iscsi_host/host13 (iscsi_host)KERNEL[1368410483.992890] add      /devices/platform/host13/session2/iscsi_session/session2 (iscsi_session)UDEV  [1368410483.994795] add      /devices/platform/host13 (scsi)UDEV  [1368410483.997767] add      /devices/platform/host13/iscsi_host/host13 (iscsi_host)UDEV  [1368410483.997797] add      /devices/platform/host13/scsi_host/host13 (scsi_host)UDEV  [1368410483.998026] add      /devices/platform/host13/session2/iscsi_session/session2 (iscsi_session)KERNEL[1368410484.018634] add      /devices/platform/host13/session2/connection2:0/iscsi_connection/connection2:0 (iscsi_connection)UDEV  [1368410484.020514] add      /devices/platform/host13/session2/connection2:0/iscsi_connection/connection2:0 (iscsi_connection)KERNEL[1368410484.280337] add      /devices/platform/host13/session2/target13:0:0 (scsi)KERNEL[1368410484.280395] add      /devices/platform/host13/session2/target13:0:0/13:0:0:0 (scsi)KERNEL[1368410484.280430] add      /devices/platform/host13/session2/target13:0:0/13:0:0:0/scsi_device/13:0:0:0 (scsi_device)UDEV  [1368410484.280683] add      /devices/platform/host13/session2/target13:0:0 (scsi)KERNEL[1368410484.281316] add      /devices/platform/host13/session2/target13:0:0/13:0:0:0/scsi_generic/sg3 (scsi_generic)KERNEL[1368410484.281371] add      /devices/platform/host13/session2/target13:0:0/13:0:0:0/bsg/13:0:0:0 (bsg)KERNEL[1368410484.287272] add      /devices/platform/host13/session2/target13:0:0/13:0:0:1 (scsi)KERNEL[1368410484.287323] add      /devices/platform/host13/session2/target13:0:0/13:0:0:1/scsi_disk/13:0:0:1 (scsi_disk)KERNEL[1368410484.287353] add      /devices/platform/host13/session2/target13:0:0/13:0:0:1/scsi_device/13:0:0:1 (scsi_device)KERNEL[1368410484.287547] add      /devices/platform/host13/session2/target13:0:0/13:0:0:1/scsi_generic/sg4 (scsi_generic)KERNEL[1368410484.287662] add      /devices/platform/host13/session2/target13:0:0/13:0:0:1/bsg/13:0:0:1 (bsg)UDEV  [1368410484.288105] add      /devices/platform/host13/session2/target13:0:0/13:0:0:1 (scsi)UDEV  [1368410484.288619] add      /devices/platform/host13/session2/target13:0:0/13:0:0:1/scsi_disk/13:0:0:1 (scsi_disk)KERNEL[1368410484.305162] add      /devices/virtual/bdi/8:32 (bdi)UDEV  [1368410484.305978] add      /devices/virtual/bdi/8:32 (bdi)UDEV  [1368410484.306235] add      /devices/platform/host13/session2/target13:0:0/13:0:0:0 (scsi)UDEV  [1368410484.307427] add      /devices/platform/host13/session2/target13:0:0/13:0:0:0/scsi_device/13:0:0:0 (scsi_device)UDEV  [1368410484.309146] add      /devices/platform/host13/session2/target13:0:0/13:0:0:1/bsg/13:0:0:1 (bsg)UDEV  [1368410484.309205] add      /devices/platform/host13/session2/target13:0:0/13:0:0:1/scsi_generic/sg4 (scsi_generic)UDEV  [1368410484.317218] add      /devices/platform/host13/session2/target13:0:0/13:0:0:0/bsg/13:0:0:0 (bsg)UDEV  [1368410484.318017] add      /devices/platform/host13/session2/target13:0:0/13:0:0:1/scsi_device/13:0:0:1 (scsi_device)UDEV  [1368410484.318073] add      /devices/platform/host13/session2/target13:0:0/13:0:0:0/scsi_generic/sg3 (scsi_generic)KERNEL[1368410484.335570] add      /devices/platform/host13/session2/target13:0:0/13:0:0:1/block/sdc (block)UDEV  [1368410484.685488] add      /devices/platform/host13/session2/target13:0:0/13:0:0:1/block/sdc (block)

可以发现新设备名为sdc

使用udevadm info -a -p /sys/block/sdc 查看设备详细信息

[root@hyperStor ~]# udevadm  info -a -p /sys/block/sdc/Udevadm info starts with the device specified by the devpath and thenwalks up the chain of parent devices. It prints for every devicefound, all possible attributes in the udev rules key format.A rule to match, can be composed by the attributes of the deviceand the attributes from one single parent device.  looking at device '/devices/platform/host13/session2/target13:0:0/13:0:0:1/block/sdc':    KERNEL=="sdc"    SUBSYSTEM=="block"    DRIVER==""    ATTR{range}=="16"    ATTR{ext_range}=="256"    ATTR{removable}=="0"    ATTR{ro}=="0"    ATTR{size}=="3919797"    ATTR{alignment_offset}=="0"    ATTR{discard_alignment}=="0"    ATTR{capability}=="52"    ATTR{stat}=="     169     1177     1346      541        0        0        0        0        0      541      541"    ATTR{inflight}=="       0        0"  looking at parent device '/devices/platform/host13/session2/target13:0:0/13:0:0:1':    KERNELS=="13:0:0:1"    SUBSYSTEMS=="scsi"    DRIVERS=="sd"    ATTRS{device_blocked}=="0"    ATTRS{type}=="0"    ATTRS{scsi_level}=="6"    ATTRS{vendor}=="IET     "    ATTRS{model}=="VIRTUAL-DISK    "    ATTRS{rev}=="0001"    ATTRS{state}=="running"    ATTRS{timeout}=="30"    ATTRS{iocounterbits}=="32"    ATTRS{iorequest_cnt}=="0xc8"    ATTRS{iodone_cnt}=="0xc8"    ATTRS{ioerr_cnt}=="0x1"    ATTRS{modalias}=="scsi:t-0x00"    ATTRS{evt_media_change}=="0"    ATTRS{dh_state}=="detached"    ATTRS{queue_depth}=="32"    ATTRS{queue_ramp_up_period}=="120000"    ATTRS{queue_type}=="none"  looking at parent device '/devices/platform/host13/session2/target13:0:0':    KERNELS=="target13:0:0"    SUBSYSTEMS=="scsi"    DRIVERS==""  looking at parent device '/devices/platform/host13/session2':    KERNELS=="session2"    SUBSYSTEMS==""    DRIVERS==""  looking at parent device '/devices/platform/host13':    KERNELS=="host13"    SUBSYSTEMS=="scsi"    DRIVERS==""  looking at parent device '/devices/platform':    KERNELS=="platform"    SUBSYSTEMS==""    DRIVERS==""

手动编辑新设备规则

[root@hyperStor ~]# ls  /etc/udev/rules.d/  -ltotal 56-rw-r--r--. 1 root root 6858 Jul 19  2011 40-hplip.rules-rw-r--r--. 1 root root  706 Jul 19  2011 56-hpmud_support.rules-rw-r--r--. 1 root root 1652 Nov 12  2010 60-fprint-autosuspend.rules-rw-r--r--. 1 root root 1060 Nov 12  2010 60-pcmcia.rules-rw-r--r--. 1 root root  316 Dec  8  2011 60-raw.rules-rw-r--r--. 1 root root  911 Mar 12 11:16 70-persistent-net.rules-rw-r--r--. 1 root root   40 Dec  8  2011 80-kvm.rules-rw-r--r--. 1 root root  320 May 15  2009 90-alsa.rules-rw-r--r--. 1 root root   83 Jul 20  2011 90-hal.rules-rw-r--r--. 1 root root   53 Dec  8  2011 91-drm-modeset.rules-rw-r--r--. 1 root root 2486 Nov 11  2010 97-bluetooth-serial.rules-rw-r--r--. 1 root root  292 Dec  8  2011 98-kexec.rules-rw-r--r--. 1 root root   54 Dec  8  2011 99-fuse.rules

创建新规则叫做 90-iscsi.rules，切记不可以100-xx.rules 命名，切记，好像最多识别到99-xx.rules

[root@hyperStor rules.d]# ls /dev/iscsi/ls: cannot access /dev/iscsi/: No such file or directory[root@hyperStor rules.d]# cat 90-iscsi.rulesACTION=="add", SUBSYSTEM=="block",DRIVERS=="sd", ENV{ID_MODEL}=="VIRTUAL-DISK",SYMLINK+="iscsi/NETDISK%n", MODE="0644"[root@hyperStor rules.d]# service iscsi restartStopping iscsi:                                            [  OK  ]Starting iscsi:                                            [  OK  ][root@hyperStor rules.d]# ls /dev/iscsi/NETDISK

ACTION: 动作为添加符号连接

注意符号：

=     赋值

对/dev/sdc 进行分区，查看UDEV名的变化‘

[root@hyperStor rules.d]# fdisk /dev/sdc -lDisk /dev/sdc: 2006 MB, 2006936064 bytes62 heads, 62 sectors/track, 1019 cylindersUnits = cylinders of 3844 * 512 = 1968128 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisk identifier: 0x4606abe9   Device Boot      Start         End      Blocks   Id  System/dev/sdc1               1         509      978267   83  Linux/dev/sdc2             510        1018      978298   83  Linux[root@hyperStor rules.d]# ls /dev/iscsi/NETDISK1  NETDISK2[root@hyperStor rules.d]# service iscsi restartStopping iscsi:                                            [  OK  ]Starting iscsi:                                            [  OK  ][root@hyperStor rules.d]# ls /dev/iscsi/NETDISK  NETDISK1  NETDISK2

[root@hyperStor rules.d]# ls /dev/iscsi/* -llrwxrwxrwx. 1 root root 6 May 13 11:12 /dev/iscsi/NETDISK -> ../sdclrwxrwxrwx. 1 root root 7 May 13 11:12 /dev/iscsi/NETDISK1 -> ../sdc1lrwxrwxrwx. 1 root root 7 May 13 11:12 /dev/iscsi/NETDISK2 -> ../sdc2