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Diffstat (limited to '')
-rw-r--r-- | Documentation/device-mapper/dm-init.rst (renamed from Documentation/device-mapper/dm-init.txt) | 89 |
1 files changed, 50 insertions, 39 deletions
diff --git a/Documentation/device-mapper/dm-init.txt b/Documentation/device-mapper/dm-init.rst index 8464ee7c01b8..e5242ff17e9b 100644 --- a/Documentation/device-mapper/dm-init.txt +++ b/Documentation/device-mapper/dm-init.rst @@ -1,5 +1,6 @@ +================================ Early creation of mapped devices -==================================== +================================ It is possible to configure a device-mapper device to act as the root device for your system in two ways. @@ -12,15 +13,17 @@ The second is to create one or more device-mappers using the module parameter The format is specified as a string of data separated by commas and optionally semi-colons, where: + - a comma is used to separate fields like name, uuid, flags and table (specifies one device) - a semi-colon is used to separate devices. -So the format will look like this: +So the format will look like this:: dm-mod.create=<name>,<uuid>,<minor>,<flags>,<table>[,<table>+][;<name>,<uuid>,<minor>,<flags>,<table>[,<table>+]+] -Where, +Where:: + <name> ::= The device name. <uuid> ::= xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx | "" <minor> ::= The device minor number | "" @@ -29,7 +32,7 @@ Where, <target_type> ::= "verity" | "linear" | ... (see list below) The dm line should be equivalent to the one used by the dmsetup tool with the ---concise argument. +`--concise` argument. Target types ============ @@ -38,32 +41,34 @@ Not all target types are available as there are serious risks in allowing activation of certain DM targets without first using userspace tools to check the validity of associated metadata. - "cache": constrained, userspace should verify cache device - "crypt": allowed - "delay": allowed - "era": constrained, userspace should verify metadata device - "flakey": constrained, meant for test - "linear": allowed - "log-writes": constrained, userspace should verify metadata device - "mirror": constrained, userspace should verify main/mirror device - "raid": constrained, userspace should verify metadata device - "snapshot": constrained, userspace should verify src/dst device - "snapshot-origin": allowed - "snapshot-merge": constrained, userspace should verify src/dst device - "striped": allowed - "switch": constrained, userspace should verify dev path - "thin": constrained, requires dm target message from userspace - "thin-pool": constrained, requires dm target message from userspace - "verity": allowed - "writecache": constrained, userspace should verify cache device - "zero": constrained, not meant for rootfs +======================= ======================================================= +`cache` constrained, userspace should verify cache device +`crypt` allowed +`delay` allowed +`era` constrained, userspace should verify metadata device +`flakey` constrained, meant for test +`linear` allowed +`log-writes` constrained, userspace should verify metadata device +`mirror` constrained, userspace should verify main/mirror device +`raid` constrained, userspace should verify metadata device +`snapshot` constrained, userspace should verify src/dst device +`snapshot-origin` allowed +`snapshot-merge` constrained, userspace should verify src/dst device +`striped` allowed +`switch` constrained, userspace should verify dev path +`thin` constrained, requires dm target message from userspace +`thin-pool` constrained, requires dm target message from userspace +`verity` allowed +`writecache` constrained, userspace should verify cache device +`zero` constrained, not meant for rootfs +======================= ======================================================= If the target is not listed above, it is constrained by default (not tested). Examples ======== An example of booting to a linear array made up of user-mode linux block -devices: +devices:: dm-mod.create="lroot,,,rw, 0 4096 linear 98:16 0, 4096 4096 linear 98:32 0" root=/dev/dm-0 @@ -71,43 +76,49 @@ This will boot to a rw dm-linear target of 8192 sectors split across two block devices identified by their major:minor numbers. After boot, udev will rename this target to /dev/mapper/lroot (depending on the rules). No uuid was assigned. -An example of multiple device-mappers, with the dm-mod.create="..." contents is shown here -split on multiple lines for readability: +An example of multiple device-mappers, with the dm-mod.create="..." contents +is shown here split on multiple lines for readability:: - vroot,,,ro, - 0 1740800 verity 254:0 254:0 1740800 sha1 - 76e9be054b15884a9fa85973e9cb274c93afadb6 - 5b3549d54d6c7a3837b9b81ed72e49463a64c03680c47835bef94d768e5646fe; - vram,,,rw, - 0 32768 linear 1:0 0, - 32768 32768 linear 1:1 0 + dm-linear,,1,rw, + 0 32768 linear 8:1 0, + 32768 1024000 linear 8:2 0; + dm-verity,,3,ro, + 0 1638400 verity 1 /dev/sdc1 /dev/sdc2 4096 4096 204800 1 sha256 + ac87db56303c9c1da433d7209b5a6ef3e4779df141200cbd7c157dcb8dd89c42 + 5ebfe87f7df3235b80a117ebc4078e44f55045487ad4a96581d1adb564615b51 Other examples (per target): -"crypt": +"crypt":: + dm-crypt,,8,ro, 0 1048576 crypt aes-xts-plain64 babebabebabebabebabebabebabebabebabebabebabebabebabebabebabebabe 0 /dev/sda 0 1 allow_discards -"delay": +"delay":: + dm-delay,,4,ro,0 409600 delay /dev/sda1 0 500 -"linear": +"linear":: + dm-linear,,,rw, 0 32768 linear /dev/sda1 0, 32768 1024000 linear /dev/sda2 0, 1056768 204800 linear /dev/sda3 0, 1261568 512000 linear /dev/sda4 0 -"snapshot-origin": +"snapshot-origin":: + dm-snap-orig,,4,ro,0 409600 snapshot-origin 8:2 -"striped": +"striped":: + dm-striped,,4,ro,0 1638400 striped 4 4096 /dev/sda1 0 /dev/sda2 0 /dev/sda3 0 /dev/sda4 0 -"verity": +"verity":: + dm-verity,,4,ro, 0 1638400 verity 1 8:1 8:2 4096 4096 204800 1 sha256 fb1a5a0f00deb908d8b53cb270858975e76cf64105d412ce764225d53b8f3cfd |