lvm interview questions
Top lvm frequently asked interview questions
I wonder if it is possible to check if a file has already been opened by another node in the same GFS cluster. For example, the fuser command runs cluster-wide in TruCluster. Is it possible to query the lock manager's data via a command or API?
Source: (StackOverflow)
I am trying to resize a logical volume on CentOS7 but am running into the following error:
resize2fs 1.42.9 (28-Dec-2013)
resize2fs: Bad magic number in super-block while trying to open /dev/mapper/centos-root
Couldn't find valid filesystem superblock.
I have tried adding a new partition (using fdisk) and using vgextend to extend the volume group, then resizing.
Resize worked fine for the logical volume using lvextend, but it failed at resize2fs.
I have also tried deleting an existing partition (using fdisk) and recreating it with a larger end block, then resizing the physical volume using lvm pvresize, followed by a resize of the logical volume using lvm lvresize. Again everything worked fine up to this point.
Once I tried to use resize2fs, using both methods as above, I received the exact same error.
Hopefully some of the following will shed some light.
fdisk -l
[root@server~]# fdisk -l
Disk /dev/xvda: 32.2 GB, 32212254720 bytes, 62914560 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk label type: dos
Disk identifier: 0x0009323a
Device Boot Start End Blocks Id System
/dev/xvda1 * 2048 1026047 512000 83 Linux
/dev/xvda2 1026048 41943039 20458496 8e Linux LVM
/dev/xvda3 41943040 62914559 10485760 8e Linux LVM
Disk /dev/mapper/centos-swap: 2147 MB, 2147483648 bytes, 4194304 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk /dev/mapper/centos-root: 29.5 GB, 29532094464 bytes, 57679872 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
pvdisplay
[root@server ~]# pvdisplay
--- Physical volume ---
PV Name /dev/xvda2
VG Name centos
PV Size 19.51 GiB / not usable 2.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 4994
Free PE 0
Allocated PE 4994
PV UUID 7bJOPh-OUK0-dGAs-2yqL-CAsV-TZeL-HfYzCt
--- Physical volume ---
PV Name /dev/xvda3
VG Name centos
PV Size 10.00 GiB / not usable 4.00 MiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 2559
Free PE 0
Allocated PE 2559
PV UUID p0IClg-5mrh-5WlL-eJ1v-t6Tm-flVJ-gsJOK6
vgdisplay
[root@server ~]# vgdisplay
--- Volume group ---
VG Name centos
System ID
Format lvm2
Metadata Areas 2
Metadata Sequence No 6
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 2
Open LV 2
Max PV 0
Cur PV 2
Act PV 2
VG Size 29.50 GiB
PE Size 4.00 MiB
Total PE 7553
Alloc PE / Size 7553 / 29.50 GiB
Free PE / Size 0 / 0
VG UUID FD7k1M-koJt-2veW-sizL-Srsq-Y6zt-GcCfz6
lvdisplay
[root@server ~]# lvdisplay
--- Logical volume ---
LV Path /dev/centos/swap
LV Name swap
VG Name centos
LV UUID KyokrR-NGsp-6jVA-P92S-QE3X-hvdp-WAeACd
LV Write Access read/write
LV Creation host, time localhost, 2014-10-09 08:28:42 +0100
LV Status available
# open 2
LV Size 2.00 GiB
Current LE 512
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:0
--- Logical volume ---
LV Path /dev/centos/root
LV Name root
VG Name centos
LV UUID ugCOcT-sTDK-M8EV-3InM-hjIg-2nwS-KeAOnq
LV Write Access read/write
LV Creation host, time localhost, 2014-10-09 08:28:42 +0100
LV Status available
# open 1
LV Size 27.50 GiB
Current LE 7041
Segments 2
Allocation inherit
Read ahead sectors auto
- currently set to 8192
Block device 253:1
I've probably done something stupid, so any help would be greatly appreciated!
Source: (StackOverflow)
How can I shut down/"unmount" a Linux lvm2 physical volume?
I plugged an external had drive to my computer. On the drive is a LVM2 PV with one volume group which has some logical volumes. I now want to remove this drive again properly.
I unmounted the filesystems, deactivated all logical volumes and the volume group.
How can I deactivate the physical volume? Or make the PV and the VG unknown to Linux again? Like just the opposite of lvmdiskscan and vgchange -a y ?
I want to leave the PV/VG and LVs on the disk intact.
Source: (StackOverflow)
I have a backup procedure that uses kpartx to read from a partitioned lvm volume.
Seldomly it happens that the device cannot be unmapped.
Right now when I try to remove the mapping I get the following:
# kpartx -d /dev/loop7
read error, sector 0
read error, sector 1
read error, sector 29
I tried dmsetup clean loop7p1 but nothing changed.
How can I free the partition without rebooting the server?
thanks
Source: (StackOverflow)
I just can't create and run new containers in Docker anymore.
But in the same time a can run previously created containers.
When I try to do something like this:
[user@host ~ ] docker run --name=fpm-5.3 debian:jessie
2014/07/12 07:34:08 Error: Error running DeviceCreate (createSnapDevice) dm_task_run failed
From docker.log:
2014/07/12 05:57:11 POST /v1.12/containers/create?name=fpm-5.3
[f56fcb6f] +job create(fpm-5.3)
Error running DeviceCreate (createSnapDevice) dm_task_run failed
[f56fcb6f] -job create(fpm-5.3) = ERR (1)
[error] server.go:1025 Error: Error running DeviceCreate (createSnapDevice) dm_task_run failed
[error] server.go:90 HTTP Error: statusCode=500 Error running DeviceCreate (createSnapDevice) dm_task_run failed
dmsetup status
docker-8:1-1210426-pool: 0 209715200 thin-pool 352 2510/524288 205173/1638400 - ro discard_passdown queue_if_no_space
But they are a lot of free space on disk.
dmsetup info
Name: docker-8:1-1210426-pool
State: ACTIVE
Read Ahead: 256
Tables present: LIVE
Open count: 1
Event number: 1
Major, minor: 252, 0
Number of targets: 1
docker info
Containers: 4
Images: 65
Storage Driver: devicemapper
Pool Name: docker-8:1-1210426-pool
Data file: /var/lib/docker/devicemapper/devicemapper/data
Metadata file: /var/lib/docker/devicemapper/devicemapper/metadata
Data Space Used: 12823.3 Mb
Data Space Total: 102400.0 Mb
Metadata Space Used: 9.9 Mb
Metadata Space Total: 2048.0 Mb
Execution Driver: native-0.2
Kernel Version: 3.14.4
docker version
Client version: 1.0.0
Client API version: 1.12
Go version (client): go1.2.2
Git commit (client): 63fe64c
Server version: 1.0.0
Server API version: 1.12
Go version (server): go1.2.2
Git commit (server): 63fe64c
Source: (StackOverflow)
I'm trying to programmatically mount a disk image created with the Fedora LiveUSB creator, and I'm encountering some issues.
From what I've been told, it's very difficult to mount LVM snapshots outside of the host system. I have both the "pristine" image and the persistent snapshot, so I thought that it should be technically possible.
Any ideas?
Source: (StackOverflow)
I have built a VG named cinder-volumes. Within this VG, I created a PV named leader-volume. Then I mounted this PV as the root filesystem of a KVM Ubuntu installation. During the installation process, I selected LVM partition.
At last, I created a snapshot for the PV leader-volume.
Now I want to read some files within my Ubuntu installation... What shall I do?
Source: (StackOverflow)
I have been reading about mysql backup through the use of lvm
I understand that you create a lvm partition and allocate a specific size to mysql, leaving enough space for the snapshots.
I read that the advantage is that backups are very quick.
Are there any pitfalls to watch out for or disadvantages?
Thanks
Source: (StackOverflow)
I'm having some issues getting my partitions to be of type primary, and not logical/extended.
Here is the relevant code in my preseed:
d-i partman-auto/disk string /dev/sda
d-i partman-auto/method string lvm
d-i partman-lvm/device_remove_lvm boolean true
d-i partman-md/device_remove_md boolean true
d-i partman-lvm/confirm boolean true
d-i partman-auto-lvm/guided_size string max
d-i partman-auto/choose_recipe select boot-root
d-i partman-auto-lvm/new_vg_name string vg00
d-i partman-auto/expert_recipe string \
boot-root :: \
512 512 512 ext3 \
$primary{ } $bootable{ } \
method{ format } format{ } \
use_filesystem{ } filesystem{ ext3 } \
mountpoint{ /boot } \
. \
2048 2048 2048 swap \
$primary{ } $lvmok{ } lv_name{ lv_swap } $defaultignore{} \
method{ swap } format{ } \
. \
1024 10000 -1 ext4 \
$primary{ } $lvmok{ } lv_name{ lv_root } $defaultignore{}\
method{ format } format{ } \
use_filesystem{ } filesystem{ ext4 } \
mountpoint{ / } \
.
d-i partman-partitioning/confirm_write_new_label boolean true
d-i partman/choose_partition select finish
d-i partman/confirm boolean true
d-i partman/confirm_nooverwrite boolean true
d-i partman-lvm/confirm_nooverwrite boolean true
The problem is, this then creates the following partition scheme:
root@ubuntu-server-1404-devit:~# fdisk /dev/sda
Command (m for help): p
Disk /dev/sda: 10.7 GB, 10737418240 bytes
255 heads, 63 sectors/track, 1305 cylinders, total 20971520 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x0009ac4d
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 2000895 999424 83 Linux
/dev/sda2 2002942 20969471 9483265 5 Extended
/dev/sda5 2002944 20969471 9483264 8e Linux LVM
I'd like to remove this unnecessary Extended / logical partition, and just have the Linux LVM partition be on sda2 (primary). Like so:
Device Boot Start End Blocks Id System
/dev/sda1 * 2048 2000895 999424 83 Linux
/dev/sda2 2002942 20969471 9483265 8e Linux LVM
Source: (StackOverflow)
I see from the LXD storage specs that LVM can be used as a backingstore. I've previously managed to get LVM working with LXC. This was very
pleasing, since it allows quota-style control of disk consumption.
How do I achieve this with LXD?
From what I understand, storage.lvm_vg_name must point to my volume
group. I've set this for a container by creating a profile, and
applying that profile to the container. The entire profile config
looks like this:
name: my-profile-name
config:
raw.lxc: |
storage.lvm_vg_name = lxc-volume-group
lxc.start.auto = 1
lxc.arch = amd64
lxc.network.type = veth
lxc.network.link = lxcbr0
lxc.network.flags = up
lxc.network.hwaddr = 00:16:3e:xx:xx:xx
lxc.cgroup.cpu.shares = 1
lxc.cgroup.memory.limit_in_bytes = 76895572
security.privileged: "false"
devices: {}
The volume group should be available and working, according to
pvdisplay on the host box:
--- Physical volume ---
PV Name /dev/sdc5
VG Name lxc-volume-group
PV Size 21.87 GiB / not usable 3.97 MiB
Allocatable yes
PE Size 4.00 MiB
Total PE 5599
Free PE 901
Allocated PE 4698
PV UUID what-ever
However after applying the profile and starting the container, it
appears to be using file backing store:
me@my-box:~# ls /var/lib/lxd/containers/container-name/rootfs/
bin boot dev etc home lib lib64 lost+found media mnt opt
proc root run sbin srv sys tmp usr var
What am I doing wrong?
Source: (StackOverflow)
I have the following Python code to create an lvm snapshot on a Linux machine.
#!/usr/bin/env python3.1
import subprocess
import logging
logging.basicConfig(filename='/var/log/lvsnap.log', filemode='w', level=logging.DEBUG)
lvm_vg = 'vg00-crunchbang'
lvm_name = 'root'
lvm_snapshot_size = '100'
def lvmCreateSnapshot(lvm_vg, lvm_name, lvm_snapshot_size):
return subprocess.check_call(['lvcreate', '-s', '-l', '+' + lvm_snapshot_size + '%FREE', '-n', lvm_name + '-snapshot', lvm_vg + '/' + lvm_name])
logging.debug('logging is working before lvm snapshot')
''' create lvm snapshot '''
lvm_create_snapshot = lvmCreateSnapshot(lvm_vg, lvm_name, lvm_snapshot_size)
if lvm_create_snapshot:
logging.debug('create lvm snapshot of %s/%s exited with status %s', lvm_vg, lvm_name, lvm_create_snapshot)
logging.debug('logging is working after lvm snapshot')
lvmCreateSnapshot runs fine and exits with 0 which should then run the logging.debug line in the if statement.
However this does not happen and instead I received the following output from the script:
> /tmp/lvmsnap.py
File descriptor 3 (/var/log/lvsnap.log) leaked on lvcreate invocation. Parent PID 7860: python3.1
Logical volume "root-snapshot" created
>
The output of the log is:
> cat /var/log/lvsnap.log
DEBUG:root:logging is working before lvm snapshot
DEBUG:root:logging is working after lvm snapshot
>
Which, as you can see has the lvm logging.debug message missing (it should appear between the 2 test logging messages I created).
Why is this happening and how can I fix it?
Source: (StackOverflow)
I need to write an execute some command in bash file and ignore the inputs.
Example
pvs --noheadings -o pv_name,vg_name,vg_size 2> /dev/null
The above command works great in command line, but when I write the same in shell, it gives me an error
like
Failed to read physical volume "2>"
Failed to read physical volume "/dev/null"
I guess it looks it as an part of the whole command. Can you please give me some suggestions on how to rectify it?
Thanks in advance.
FULLCODE
#------------------------------
main() {
pv_cmd='pvs'
nh='--noheadings'
sp=' '
op='-o'
vgn='vg_name'
pvn='pv_name'
pvz='pv_size'
cm=','
tonull=' 2 > /dev/null '
pipe='|'
#cmd=$pv_cmd$sp$nh$sp$op$sp$vgn$cm$pvn$cm$pvz$sp$pipe$tonull #line A
cmd='pvs --noheadings -o vg_name,pv_name,pv_size 2> /dev/null' #line B
echo -n "Cmd="
echo $cmd
$cmd
}
main
#-----------------------------------------------------
If you look at the Line A & B both the versions are there, although one is commented out.....
Source: (StackOverflow)
I am trying to run "lvs" in a perl script to parse its output.
my $output = `lvs --noheadings --separator : --units m --nosuffix 2>&1`;
my $result = $?;
if ($result != 0 || length($output) == 0) {
printf STDERR "Get list of LVs failed (exit result: %d): %s\n",
$result, $output;
exit(1);
}
printf "SUCCESS:\n%s\n", $output;
When I run the above script from a terminal window it runs fine. If I run via cron it fails:
Get list of LVs failed (exit result: -1):
Note the lack of any output (stdout + stderr)
If I run the same "lvs --noheadings --separator : --units m --nosuffix" command directly in cron, it runs and outputs just fine.
If I modify the perl script to use open3() I also get the same failure with no output.
If I add "-d -d -d -d -d -v -v -v" to the lvs command to enable verbose/debug output I see that when I run the perl script from terminal, but there is no output when run via cron/perl.
I'm running this on RHEL 7.2 with /usr/bin/perl (5.16.3)
Any suggestions???
Source: (StackOverflow)
I have just made a lvm snapshot of /opt partition then mounted that lvm to a /data.Is there is any way to take incremental lvm snapshots ?
Source: (StackOverflow)