16 understanding device mapper and LVM device names lvdisplay, pvscan, pvdisplay -m

By OK -

The Device-mapper is a component of the linux kernel (since version 2.6) that supports logical volume management. It is required by LVM2 and EVMS. The original LVM (included in stock 2.4 kernels) does not use it.


Kernel over device mapper can communicate with LVM, LUKS, RAID

kernel -> device-mapper -> LVM,LUKS, RAID
kernel -> VFS(xfs, ext4)

device-mapper names:
/dev/dm-0
/dev/dm-1

above names could change, so we have mapper names
/dev/mapper/vg-lv --->symbolic name --> /dev/dm-0...n



lvdisplay - display attributes of a logical volume
[root@localhost /]# lvdisplay /dev/vgmyvg/lvmylv 
File descriptor 22 (socket:[27108]) leaked on lvdisplay invocation. Parent PID 3225: -bash
  --- Logical volume ---
  LV Path                /dev/vgmyvg/lvmylv
  LV Name                lvmylv
  VG Name                vgmyvg
  LV UUID                rw55aw-zT0Y-gORa-AXkx-twj5-K0HY-JvMVBz
  LV Write Access        read/write
  LV Creation host, time localhost.localdomain, 2017-08-02 16:46:54 -0400
  LV Status              available
  # open                 1
  LV Size                96.00 MiB
  Current LE             24
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     8192
  Block device           253:2
 
[root@localhost /]#

pvscan scans all supported LVM block devices in the system for physical volumes.
[root@localhost /]# pvscan
File descriptor 22 (socket:[27108]) leaked on pvscan invocation. Parent PID 3225: -bash
  PV /dev/sdb3   VG vgmyvg          lvm2 [96.00 MiB / 0    free]
  PV /dev/sda2   VG cl              lvm2 [19.00 GiB / 0    free]
  Total: 2 [19.09 GiB] / in use: 2 [19.09 GiB] / in no VG: 0 [0   ]
[root@localhost /]#


pvdisplay - display attributes of a physical volume 

[root@localhost /]# pvdisplay -m
File descriptor 22 (socket:[27108]) leaked on pvdisplay invocation. Parent PID 3225: -bash
  --- Physical volume ---
  PV Name               /dev/sdb3
  VG Name               vgmyvg
  PV Size               100.00 MiB / not usable 4.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              24
  Free PE               0
  Allocated PE          24
  PV UUID               Cxhik5-4hkZ-1JLA-3V0q-7mLS-cCYK-Q8vFXv
 
  --- Physical Segments ---
  Physical extent 0 to 23:
    Logical volume      /dev/vgmyvg/lvmylv
    Logical extents     0 to 23
 
  --- Physical volume ---
  PV Name               /dev/sda2
  VG Name               cl
  PV Size               19.00 GiB / not usable 3.00 MiB
  Allocatable           yes (but full)
  PE Size               4.00 MiB
  Total PE              4863
  Free PE               0
  Allocated PE          4863
  PV UUID               WmnwtU-f4Wk-Co7D-Ouyx-mLUw-wy5U-PXV1sg
 
  --- Physical Segments ---
  Physical extent 0 to 511:
    Logical volume      /dev/cl/swap
    Logical extents     0 to 511
  Physical extent 512 to 4862:
    Logical volume      /dev/cl/root
    Logical extents     0 to 4350
 
[root@localhost /]#



Comments

Post a Comment

Popular posts from this blog

HAproxy logging

By OK -
ubuntu@ubuntu:/etc/haproxy$ cat /etc/rsyslog.d/haproxy.conf # Create an additional socket in haproxy's chroot in order to allow logging via # /dev/log to chroot'ed HAProxy processes $ModLoad imudp $UDPServerRun 514 local0.* -/var/log/haproxy-0.log local1.* -/var/log/haproxy-1.log ### keep logs in localhost ## $AddUnixListenSocket /var/lib/haproxy/dev/log ------------------- ubuntu@ubuntu:/etc/haproxy$ cat /etc/haproxy/haproxy.cfg global chroot /var/lib/haproxy user haproxy group haproxy log 127.0.0.1   local0         log 127.0.0.1   local1 notice daemon frontend www     bind 192.168.40.128:8282    # haproxy public IP     default_backend as-backend    # backend used backend as-backend    balance leastconn    mode http  server as1 192.168.40.128:8082 check    # application srv 1 defaults log ...
Read more

teamcity Automatic Agent Start under Linux

By OK -
Automatic Agent Start under Linux To run agent automatically on the machine boot under Linux, configure daemon process with the  agent.sh start  command to start it and  agent.sh stop  command to stop it. Refer to an example procedure below: 1. Navigate to the services start/stop services scripts directory: cd /etc/init.d/ 2. Open the build agent service script: sudo vim buildAgent 3. Paste the following into the file : #!/bin/sh ### BEGIN INIT INFO # Provides: TeamCity Build Agent # Required-Start: $remote_fs $syslog # Required-Stop: $remote_fs $syslog # Default-Start: 2 3 4 5 # Default-Stop: 0 1 6 # Short-Description: Start build agent daemon at boot time # Description: Enable service provided by daemon. ### END INIT INFO #Provide the correct user name: USER="agentuser" case "$1" in start) su - $USER -c "cd BuildAgent/bin ; ./agent.sh start" ;; stop) su - $USER -c "cd BuildAgent/bin ; ./agent....
Read more

NFS mount add in fstab _netdev instead of default | firewall-cmd --list-all

By OK -
Redhat recommends us to add  _netdev  option for NFS file system in /etc/fstab. So that they can be mounted after starting the networking service. Alternative ways to refer to partitions: Label : LABEL=label Network ID Samba : //server/share NFS : server:/share SSHFS : sshfs#user@server:/share Device : /dev/sdxy (not recommended) Example #1 //192.168.1.134/share_name /mnt/share_name cifs username=server_user,password=server_password,_netdev 0 0 ^ Path to your share ^ Mountpoint ^ Username ^ Password ^ See note A Note A: The  _netdev  options makes sure the mount is only attempted AFTER a network connection has been established. Example #2 10.10.10.1:/vol1/fs1 /data nfs defaults,_netdev 0 0 ============================ [root@localhost ~]# firewall-cmd --list-all public   target: default   icmp-block-inversion: no   interfaces:   sources:   services: dhcpv6-client high-availabi...
Read more