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authorJasper Ras <jras@hostnet.nl>2025-01-19 21:14:51 +0100
committerJasper Ras <jras@hostnet.nl>2025-01-19 21:14:51 +0100
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+#linux #device-mapper
+
+---
+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?
+[[1 projects/Inwerken Mohammed/TODO]]
+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) \ No newline at end of file