I have a Juniper router which uses Junos(based on FreeBSD) operating system where I can backup certain partitions from router CLI. Under the hood router starts the restore process and copies /dev/ad0s1a to /dev/ad1s1a and /dev/ad0s1e to /dev/ad1s1e. FreeBSD partitions before this copy operation are following:
# bsdlabel /dev/ad0s1
# /dev/ad0s1:
8 partitions:
# size offset fstype [fsize bsize bps/cpg]
a: 451556 0 4.2BSD 2048 16384 28224
c: 501728 0 unused 0 0 # "raw" part, don't edit
e: 50172 451556 4.2BSD 2048 16384 3136
# bsdlabel /dev/ad1s1
# /dev/ad1s1:
8 partitions:
# size offset fstype [fsize bsize bps/cpg]
a: 451556 0 4.2BSD 2048 16384 96
b: 4194288 451556 swap
c: 58605057 0 unused 0 0 # "raw" part, don't edit
e: 50172 4645844 4.2BSD 2048 16384 105
f: 53909041 4696016 4.2BSD 2048 16384 89
#
After the copy operation they are following:
# bsdlabel /dev/ad0s1
# /dev/ad0s1:
8 partitions:
# size offset fstype [fsize bsize bps/cpg]
a: 451556 0 4.2BSD 2048 16384 28224
c: 501728 0 unused 0 0 # "raw" part, don't edit
e: 50172 451556 4.2BSD 2048 16384 3136
# bsdlabel /dev/ad1s1
# /dev/ad1s1:
8 partitions:
# size offset fstype [fsize bsize bps/cpg]
a: 451556 0 4.2BSD 2048 16384 28224
b: 4194288 451556 swap
c: 58605057 0 unused 0 0 # "raw" part, don't edit
e: 50172 4645844 4.2BSD 2048 16384 3136
f: 53909041 4696016 4.2BSD 2048 16384 89
#
从bsdlabel复制操作之前和之后的输出可以看出，在bps/cpg对/dev/ad1s1a和/dev/ad1s1e分区进行处理之后，计数器会增加。我是否纠正过在复制操作/dev/ad1s1a和之前/dev/ad1s1e存在分区，但它们几乎为空的情况？因此，此复制操作可能将整个文件系统从镜像/dev/ad0s1a到，/dev/ad1s1a并镜像/dev/ad0s1e到/dev/ad1s1e？
是的，我相信你是正确的。尽管bsdlabel提供了有关分区的信息，但在bps/cpg列中还提供了有关分区中文件系统的一些信息。有关更多信息，请参见bsdlabel手册页。该restore命令可能正在从该dump命令接收数据。有关更多详细信息，请参见还原手册页和转储手册页。
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