From eae6b57f17f5065a2bd3f130668043693f579cb4 Mon Sep 17 00:00:00 2001 From: Jasper Ras Date: Fri, 11 Apr 2025 16:02:40 +0200 Subject: vault backup: 2025-04-11 16:02:40 --- Device mapper.md | 30 ++++++++++++++++++++++++++++++ 1 file changed, 30 insertions(+) create mode 100644 Device mapper.md (limited to 'Device mapper.md') 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) \ No newline at end of file -- cgit v1.2.3