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| author | Jasper Ras <jaspert.ras@gmail.com> | 2025-04-18 21:01:49 +0200 |
|---|---|---|
| committer | Jasper Ras <jaspert.ras@gmail.com> | 2025-04-18 21:01:49 +0200 |
| commit | a8a8e1f984f20c8008f3a5f57cd39b416eb73104 (patch) | |
| tree | 2262794b52d82c5fd9cbc55b503b52fafbd3af8a /Device mapper.md | |
| parent | 5fa69499917fab7a026c90c8321dbcc22734106a (diff) | |
| parent | ab409a3701bf59dd73dc1e0324376bdac8b6d74f (diff) | |
vault backup: 2025-04-18 21:01:49
Diffstat (limited to 'Device mapper.md')
| -rw-r--r-- | Device mapper.md | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/Device mapper.md b/Device mapper.md new file mode 100644 index 0000000..150338b --- /dev/null +++ b/Device mapper.md @@ -0,0 +1,30 @@ +--- +tags: + - linux + - devices + - kernel +--- +Device mapper is a kernel driver to map physical block devices to virtual ones; this means that for example we can have many physical devices be represented by a single virtual one (linear mapping). + +How does it work? +What is its function in relation to multipath? + +Logical devices using device-mapper can be managed using `man 8 dmsetup` +``` +[jasras@n04.compute.vps2-lej1 ~]$ sudo dmsetup info 3600a098038314d736724566a67346538 +Name: 3600a098038314d736724566a67346538 +State: ACTIVE +Read Ahead: 256 +Tables present: LIVE +Open count: 1 +Event number: 3 +Major, minor: 253, 12 +Number of targets: 1 +UUID: mpath-3600a098038314d736724566a67346538 +``` + +If dmsetup cannot remove a device because a process still has it open, but lsof does not show any processes that open it, use `-f` which replaces the device with a fake that rejects all I/O. + +--- +[device-mapper](https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/7/html/logical_volume_manager_administration/device_mapper#device_mapper) +[dmsetup](https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/7/html/logical_volume_manager_administration/dmsetup#dmsetup)
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