zdb命令本身是可以查阅man zdb或zdb –help提供帮助的，无奈帮助太过简洁，而且省略了很多非常重要、有用的参数，正巧这几天研究，就记录一下。
以下假设pool的名称为case2.2：
zdb –uuu case2.2
作用：显示case2.2的活动uberblock，并显示其DVA,结果如下图所示：
zdb –ddddd case2.2
作用：显示所有文件系统集合上的对象的详细摘要信息，导出后有用信息太多了。足够看N久的了。
zdb –ddddd case2.2/ 4
作用：显示case2.2用户文件系统下第4号节点文件的摘要信息，包括dva信息等，如果是zdb –ddddd case2.2 4，则表示是meta集合的第4号节点的摘要信息。
#!/bin/bash echo "readzfsobj.sh" touch $3 zdb -ddddd $1/ $2 |sed -n "/^ *[0123456789abcdef]* *L0 * /p" |awk '{print $3}'|while read line do #echo "zy:$line" zdb -R $1 $line:r >>$3 done
作用：使用此shell脚本，配合zdb命令，即可导出指定对象，主要用于研究目录等非文件集合数据。如通过ls -i 命令知道某个目录的节点号，执行
readzfsobj.sh case2.2 4 root.img
即可将文件系统根目录块导出成一个普通文件，再用二进制工具查看则较容易读懂mzap，fatzap的结构。
大致原理：假设有一大目录id是13，因执行zdb -ddddd case2.2 13时，会列出如下图所示目录的地址索引信息，通过sed命令过滤出这些行，再通过awk打印其中的DVA。最后，通过一行一行地执行zdb -R 命令把块导出后输入到目标文件中(本示例为去掉压缩选项后的处理方案，如果有压缩，需做针对性处置)。
zdb -m
zdb -m
[root@localhost ~]# zdb -m case4 sdb1 4 Metaslabs: vdev 0 metaslabs 119 offset spacemap free --------------- ------------------- --------------- ------------- metaslab 4 offset 40000000 spacemap 42 free 5.05M
[root@localhost ~]# zdb -mm case4 sdb1 4 Metaslabs: vdev 0 metaslabs 119 offset spacemap free --------------- ------------------- --------------- ------------- metaslab 4 offset 40000000 spacemap 42 free 5.05M On-disk histogram: fragmentation 11 9: 2 ** 10: 0 11: 0 12: 0 13: 1 * 14: 1 * 15: 2 ** 16: 0 17: 0 18: 0 19: 0 20: 0 21: 0 22: 1 *
[root@localhost ~]# zdb -mmm case4 sdb1 4 Metaslabs: vdev 0 metaslabs 119 offset spacemap free --------------- ------------------- --------------- ------------- metaslab 4 offset 40000000 spacemap 42 free 5.05M segments 19 maxsize 4.44M freepct 1% In-memory histogram: 9: 3 *** 10: 2 ** 11: 1 * 12: 0 13: 1 * 14: 6 ****** 15: 2 ** 16: 2 ** 17: 1 * 18: 0 19: 0 20: 0 21: 0 22: 1 * On-disk histogram: fragmentation 11 9: 2 ** 10: 0 11: 0 12: 0 13: 1 * 14: 1 * 15: 2 ** 16: 0 17: 0 18: 0 19: 0 20: 0 21: 0 22: 1 *
[root@localhost ~]# zdb -mmmm case4 sdb1 4 Metaslabs: vdev 0 metaslabs 119 offset spacemap free --------------- ------------------- --------------- ------------- metaslab 4 offset 40000000 spacemap 42 free 5.05M segments 19 maxsize 4.44M freepct 1% In-memory histogram: 9: 3 *** 10: 2 ** 11: 1 * 12: 0 13: 1 * 14: 6 ****** 15: 2 ** 16: 2 ** 17: 1 * 18: 0 19: 0 20: 0 21: 0 22: 1 * On-disk histogram: fragmentation 11 9: 2 ** 10: 0 11: 0 12: 0 13: 1 * 14: 1 * 15: 2 ** 16: 0 17: 0 18: 0 19: 0 20: 0 21: 0 22: 1 * [ 0] ALLOC: txg 109, pass 1 [ 1] A range: 0040000000-00403e9c00 size: 3e9c00 [ 2] FREE: txg 109, pass 1 [ 3] F range: 00403e4000-00403e4800 size: 000800 [ 4] ALLOC: txg 109, pass 2 [ 5] A range: 00403e9c00-00403f7000 size: 00d400 [ 6] ALLOC: txg 109, pass 3 [ 7] A range: 00403f7000-00403fb000 size: 004000 [ 8] ALLOC: txg 111, pass 1 [ 9] A range: 00403fb000-00413fb000 size: 1000000 [ 10] A range: 00413fb000-00423fb000 size: 1000000 [ 11] A range: 00423fb000-0042a8cc00 size: 691c00 [ 12] FREE: txg 111, pass 1 [ 13] F range: 00403c0000-00403e4000 size: 024000 [ 14] F range: 00403e4800-00403e9c00 size: 005400 [ 15] F range: 0042a87000-0042a87800 size: 000800 [ 16] ALLOC: txg 111, pass 2 [ 17] A range: 0042a8cc00-0042a97c00 size: 00b000 [ 18] ALLOC: txg 111, pass 3 [ 19] A range: 0042a97c00-0042a9ec00 size: 007000 [ 20] ALLOC: txg 112, pass 1 [ 21] A range: 0042a9ec00-0042ac5000 size: 026400 [ 22] FREE: txg 112, pass 1 [ 23] F range: 0042a6f000-0042a87000 size: 018000 [ 24] F range: 0042a87800-0042a8cc00 size: 005400 [ 25] F range: 0042abf400-0042abfc00 size: 000800 [ 26] ALLOC: txg 112, pass 2 [ 27] A range: 0042ac5000-0042ad1000 size: 00c000 [ 28] FREE: txg 112, pass 2 [ 29] F range: 00403e9c00-00403eac00 size: 001000 [ 30] F range: 00403eae00-00403ebe00 size: 001000 [ 31] F range: 00403ec000-00403fb000 size: 00f000 [ 32] ALLOC: txg 112, pass 3 [ 33] A range: 0042ad1000-0042ad7000 size: 006000 [ 34] ALLOC: txg 114, pass 1 [ 35] A range: 00403c0000-00403e8800 size: 028800 [ 36] A range: 0042ad7000-0043ad7000 size: 1000000 [ 37] A range: 0043ad7000-004448b000 size: 9b4000 [ 38] FREE: txg 114, pass 1 [ 39] F range: 0042a9ec00-0042a9ee00 size: 000200 [ 40] F range: 0042a9f400-0042aa3400 size: 004000 [ 41] F range: 0042aa7400-0042abf400 size: 018000 [ 42] F range: 0042abfc00-0042ac5000 size: 005400 [ 43] F range: 0044485400-0044485c00 size: 000800 [ 44] ALLOC: txg 114, pass 2 [ 45] A range: 004448b000-0044496000 size: 00b000 [ 46] FREE: txg 114, pass 2 [ 47] F range: 0042a8cc00-0042a9bc00 size: 00f000 [ 48] F range: 0042a9cc00-0042a9dc00 size: 001000 [ 49] ALLOC: txg 114, pass 3 [ 50] A range: 0044496000-004449d000 size: 007000 [ 51] ALLOC: txg 117, pass 1 [ 52] A range: 004449d000-004549d000 size: 1000000 [ 53] A range: 004549d000-0045a07a00 size: 56aa00 [ 54] FREE: txg 117, pass 1 [ 55] F range: 00403c0000-00403c0400 size: 000400 [ 56] F range: 0042ad8a00-0042ad8c00 size: 000200 [ 57] F range: 004441d400-0044421400 size: 004000 [ 58] F range: 0044469400-0044485400 size: 01c000 [ 59] F range: 0044485c00-004448b000 size: 005400 [ 60] F range: 0045a01e00-0045a02600 size: 000800 [ 61] ALLOC: txg 117, pass 2 [ 62] A range: 0045a07a00-0045a12a00 size: 00b000 [ 63] FREE: txg 117, pass 2 [ 64] F range: 0042a9bc00-0042a9cc00 size: 001000 [ 65] F range: 0042a9dc00-0042a9ec00 size: 001000 [ 66] F range: 0042ac6000-0042ad6000 size: 010000 [ 67] ALLOC: txg 117, pass 3 [ 68] A range: 0045a12a00-0045a16a00 size: 004000 [ 69] ALLOC: txg 118, pass 1 [ 70] A range: 00403ec000-00403f4000 size: 008000 [ 71] A range: 0045a16a00-0046a16a00 size: 1000000 [ 72] A range: 0046a16a00-0047a16a00 size: 1000000 [ 73] A range: 0047a16a00-0047dbca00 size: 3a6000 [ 74] FREE: txg 118, pass 1 [ 75] F range: 0042ad7200-0042ad7400 size: 000200 [ 76] F range: 00453ffc00-00453ffe00 size: 000200 [ 77] F range: 004588b000-004588b400 size: 000400 [ 78] F range: 00458be800-00458bec00 size: 000400 [ 79] F range: 004593de00-0045941e00 size: 004000 [ 80] F range: 00459d9e00-00459dde00 size: 004000 [ 81] F range: 00459e1e00-0045a01e00 size: 020000 [ 82] F range: 0045a02600-0045a07a00 size: 005400 [ 83] F range: 0047db6e00-0047db7600 size: 000800 [ 84] ALLOC: txg 118, pass 2 [ 85] A range: 0047dbca00-0047dc7a00 size: 00b000 [ 86] FREE: txg 118, pass 2 [ 87] F range: 004448b000-004449a000 size: 00f000 [ 88] ALLOC: txg 118, pass 3 [ 89] A range: 0047dc7a00-0047dcba00 size: 004000 [ 90] ALLOC: txg 119, pass 1 [ 91] A range: 0047dcba00-0048dcba00 size: 1000000 [ 92] A range: 0048dcba00-0049dcba00 size: 1000000 [ 93] A range: 0049dcba00-004ab07a00 size: d3c000 [ 94] FREE: txg 119, pass 1 [ 95] F range: 0047abde00-0047abee00 size: 001000 [ 96] F range: 0047d82e00-0047d86e00 size: 004000 [ 97] F range: 0047d9ae00-0047db6e00 size: 01c000 [ 98] F range: 0047db7600-0047dbca00 size: 005400 [ 99] F range: 004ab01e00-004ab02600 size: 000800 [ 100] ALLOC: txg 119, pass 2 [ 101] A range: 004ab07a00-004ab12a00 size: 00b000 [ 102] FREE: txg 119, pass 2 [ 103] F range: 0045a07a00-0045a16a00 size: 00f000 [ 104] ALLOC: txg 119, pass 3 [ 105] A range: 004ab12a00-004ab16a00 size: 004000 [ 106] ALLOC: txg 120, pass 1 [ 107] A range: 004ab16a00-004bb16a00 size: 1000000 [ 108] A range: 004bb16a00-004cb16a00 size: 1000000 [ 109] A range: 004cb16a00-004db16a00 size: 1000000 [ 110] A range: 004db16a00-004db18000 size: 001600 [ 111] FREE: txg 120, pass 1 [ 112] F range: 0047dd3e00-0047dd6600 size: 002800 [ 113] F range: 004aab5a00-004aabda00 size: 008000 [ 114] F range: 004aac1e00-004aac5e00 size: 004000 [ 115] F range: 004aae5e00-004ab01e00 size: 01c000 [ 116] F range: 004ab02600-004ab07a00 size: 005400 [ 117] F range: 004db12400-004db12c00 size: 000800 [ 118] ALLOC: txg 120, pass 2 [ 119] A range: 004db18000-004db23000 size: 00b000 [ 120] FREE: txg 120, pass 2 [ 121] F range: 0047dbca00-0047dcba00 size: 00f000 [ 122] ALLOC: txg 120, pass 3 [ 123] A range: 004db23000-004db27000 size: 004000 [ 124] ALLOC: txg 121, pass 1 [ 125] A range: 004db27000-004e090c00 size: 569c00 [ 126] FREE: txg 121, pass 1 [ 127] F range: 004dabe000-004dac6000 size: 008000 [ 128] F range: 004daf6400-004db12400 size: 01c000 [ 129] F range: 004db12c00-004db18000 size: 005400 [ 130] F range: 004e08b000-004e08b800 size: 000800 [ 131] ALLOC: txg 121, pass 2 [ 132] A range: 004e090c00-004e09bc00 size: 00b000 [ 133] FREE: txg 121, pass 2 [ 134] F range: 004ab07a00-004ab16a00 size: 00f000 [ 135] ALLOC: txg 121, pass 3 [ 136] A range: 004e09bc00-004e09fc00 size: 004000 [ 137] ALLOC: txg 123, pass 1 [ 138] A range: 00403c0000-00403c0400 size: 000400 [ 139] A range: 00403e8800-00403eac00 size: 002400 [ 140] A range: 00403eae00-00403ebe00 size: 001000 [ 141] A range: 00403f4000-00403fb000 size: 007000 [ 142] A range: 0042a6f000-0042a9ee00 size: 02fe00 [ 143] A range: 0042a9f400-0042aa3400 size: 004000 [ 144] A range: 0042aa7400-0042ac5000 size: 01dc00 [ 145] A range: 0042ac6000-0042ad6000 size: 010000 [ 146] A range: 0042ad7200-0042ad7400 size: 000200 [ 147] A range: 0042ad8a00-0042ad8c00 size: 000200 [ 148] A range: 004441d400-0044421400 size: 004000 [ 149] A range: 0044469400-004449a000 size: 030c00 [ 150] A range: 00453ffc00-00453ffe00 size: 000200 [ 151] A range: 004588b000-004588b400 size: 000400 [ 152] A range: 00458be800-00458bec00 size: 000400 [ 153] A range: 004593de00-0045941e00 size: 004000 [ 154] A range: 00459d9e00-00459dde00 size: 004000 [ 155] A range: 00459e1e00-0045a16a00 size: 034c00 [ 156] A range: 0047abde00-0047abee00 size: 001000 [ 157] A range: 0047d82e00-0047d86e00 size: 004000 [ 158] A range: 0047d9ae00-0047dcba00 size: 030c00 [ 159] A range: 0047dd3e00-0047dd6600 size: 002800 [ 160] A range: 004aab5a00-004aabda00 size: 008000 [ 161] A range: 004aac1e00-004aac5e00 size: 004000 [ 162] A range: 004aae5e00-004ab07a00 size: 021c00 [ 163] A range: 004db12400-004db12c00 size: 000800 [ 164] A range: 004e09fc00-004f09fc00 size: 1000000 [ 165] A range: 004f09fc00-004fb92e00 size: af3200 [ 166] FREE: txg 123, pass 1 [ 167] F range: 0042a9ee00-0042a9f400 size: 000600 [ 168] F range: 0042aa3400-0042aa7400 size: 004000 [ 169] F range: 0046680800-0046680e00 size: 000600 [ 170] F range: 00474f7400-00474f7600 size: 000200 [ 171] F range: 0047c5ae00-0047c5ee00 size: 004000 [ 172] F range: 0047cb6e00-0047cbae00 size: 004000 [ 173] F range: 0047d72e00-0047d76e00 size: 004000 [ 174] F range: 004ac8cc00-004ac91200 size: 004600 [ 175] F range: 004daca400-004dace400 size: 004000 [ 176] F range: 004e067000-004e08b000 size: 024000 [ 177] F range: 004e08b800-004e090c00 size: 005400 [ 178] F range: 004fb8d200-004fb8da00 size: 000800 [ 179] ALLOC: txg 123, pass 2 [ 180] A range: 004fb92e00-004fb9de00 size: 00b000 [ 181] FREE: txg 123, pass 2 [ 182] F range: 004db18000-004db27000 size: 00f000 [ 183] ALLOC: txg 123, pass 3 [ 184] A range: 004fb9de00-004fba1e00 size: 004000 [ 185] FREE: txg 125, pass 1 [ 186] F range: 004fb8e600-004fb92e00 size: 004800 [ 187] FREE: txg 125, pass 2 [ 188] F range: 004e090c00-004e09fc00 size: 00f000 [ 189] FREE: txg 127, pass 2 [ 190] F range: 00403eac00-00403eae00 size: 000200 [ 191] F range: 00403ebe00-00403ec000 size: 000200 [ 192] F range: 004449a000-004449c000 size: 002000 [ 193] F range: 004fb92e00-004fba1e00 size: 00f000
引用：http://cuddletech.com/?p=407 中的一段zdb命令的说明
There are 3 arguments that are really the core ones of interest, but fefore we get to them, you absolutely must understand something unique about zdb. ZDB is like a magnifying glass, at default magnification you can see that its tissue, turn up the magnification and you see that it has veins, turn it up again and you see how intricate the system is, crank it up one more time and you can see blood cells themselves. With zdb, each time we repeat an argument we increase the verbosity and thus dig deeper. For instance, zdb -d will list the datasets of a pool, but zdb -dd will output the list of objects within the pool. Thus, when you really zoom in you’ll see commands that look really odd like zdb -ddddddddd. This takes a little practice to get the hang of, so please toy around on a small test pool to get the hang of it.
Now, here are summaries of the 3 primary arguments you’ll use and how things change as you crank up the verbosity:
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zdb -b pool: This will traverse blocks looking for leaks like the default form.
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-bb: Outputs a breakdown of space (block) usage for various ZFS object types.
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-bbb: Same as above, but includes breakdown by DMU/SPA level (L0-L6).
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-bbbb: Same as above, but includes line line per object with details about it, including compression, checksum, DVA, object ID, etc.
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-bbbbb…: Same as above.
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zdb -d dataset: This will output a list of objects within a dataset. More d’s means more verbosity:
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-d: Output list of datasets, including ID, cr_txg, size, and number of objects.
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–dd: Output concise list of objects within the dataset, with object id, lsize, asize, type, etc.
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-ddd: Same as dd.
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-dddd: Outputs list of datasets and objects in detail, including objects path (filename), a/c/r/mtime, mode, etc.
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-ddddd: Same as previous, but includes indirect block addresses (DVAs) as well.
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-dddddd….: Same as above.
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zdb -R pool:vdev_specifier:offset:size[:flags]: Given a DVA, outputs object contents in hex display format. If given the :r flag it will output in raw binary format. This can be used for manual recovery of files.