OpenVZ: Mounting Host Devices/Partitions/Directories In A Container With Bind Mounts (Debian/Ubuntu)
Version 1.0
Author: Falko Timme
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Sometimes you are in a situation where you need to mount a hard drive, partiiton or directory from the OpenVZ host inside an OpenVZ container - for example, you add a fast SSD to the host and want to put your container's MySQL databases on it to make MySQL faster. This tutorial explains how you can mount host devices/partitions/directories in an OpenVZ container with bind mounts.
I do not issue any guarantee that this will work for you!
1 Preliminary Note
In this tutorial I have an OpenVZ container with the container ID 101 which is running MySQL. I add a second hard drive to the host and want to put the container's MySQL directory /var/lib/mysql on the second hard drive.
2 Preparing The Host
Host:
If you have added a new hard drive to the host, you should see it in the output of...
fdisk -l
... and you should see that it is unformatted (unless you have created partitions on it previously) - in this example the hard drive is /dev/sdb:
root@server1:~# fdisk -l
Disk /dev/sda: 32.2 GB, 32212254720 bytes
255 heads, 63 sectors/track, 3916 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00029d5c
Device Boot Start End Blocks Id System
/dev/sda1 * 1 3793 30461952 83 Linux
/dev/sda2 3793 3917 992257 5 Extended
/dev/sda5 3793 3917 992256 82 Linux swap / Solaris
Disk /dev/sdb: 32.2 GB, 32212254720 bytes
255 heads, 63 sectors/track, 3916 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/sdb doesn't contain a valid partition table
root@server1:~#
Let's create one single partition on it:
fdisk /dev/sdb
root@server1:~# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or OSF disklabel
Building a new DOS disklabel with disk identifier 0x31e0dc4b.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.
Warning: invalid flag 0x0000 of partition table 4 will be corrected by w(rite)
WARNING: DOS-compatible mode is deprecated. It's strongly recommended to
switch off the mode (command 'c') and change display units to
sectors (command 'u').
Command (m for help): <-- n
Command action
e extended
p primary partition (1-4)
<-- p
Partition number (1-4): <-- 1
First cylinder (1-3916, default 1): <-- ENTER
Using default value 1
Last cylinder, +cylinders or +size{K,M,G} (1-3916, default 3916): <-- ENTER
Using default value 3916
Command (m for help): <-- t
Selected partition 1
Hex code (type L to list codes): <-- L
0 Empty 24 NEC DOS 81 Minix / old Lin bf Solaris
1 FAT12 39 Plan 9 82 Linux swap / So c1 DRDOS/sec (FAT-
2 XENIX root 3c PartitionMagic 83 Linux c4 DRDOS/sec (FAT-
3 XENIX usr 40 Venix 80286 84 OS/2 hidden C: c6 DRDOS/sec (FAT-
4 FAT16 <32M 41 PPC PReP Boot 85 Linux extended c7 Syrinx
5 Extended 42 SFS 86 NTFS volume set da Non-FS data
6 FAT16 4d QNX4.x 87 NTFS volume set db CP/M / CTOS / .
7 HPFS/NTFS 4e QNX4.x 2nd part 88 Linux plaintext de Dell Utility
8 AIX 4f QNX4.x 3rd part 8e Linux LVM df BootIt
9 AIX bootable 50 OnTrack DM 93 Amoeba e1 DOS access
a OS/2 Boot Manag 51 OnTrack DM6 Aux 94 Amoeba BBT e3 DOS R/O
b W95 FAT32 52 CP/M 9f BSD/OS e4 SpeedStor
c W95 FAT32 (LBA) 53 OnTrack DM6 Aux a0 IBM Thinkpad hi eb BeOS fs
e W95 FAT16 (LBA) 54 OnTrackDM6 a5 FreeBSD ee GPT
f W95 Ext'd (LBA) 55 EZ-Drive a6 OpenBSD ef EFI (FAT-12/16/
10 OPUS 56 Golden Bow a7 NeXTSTEP f0 Linux/PA-RISC b
11 Hidden FAT12 5c Priam Edisk a8 Darwin UFS f1 SpeedStor
12 Compaq diagnost 61 SpeedStor a9 NetBSD f4 SpeedStor
14 Hidden FAT16 <3 63 GNU HURD or Sys ab Darwin boot f2 DOS secondary
16 Hidden FAT16 64 Novell Netware af HFS / HFS+ fb VMware VMFS
17 Hidden HPFS/NTF 65 Novell Netware b7 BSDI fs fc VMware VMKCORE
18 AST SmartSleep 70 DiskSecure Mult b8 BSDI swap fd Linux raid auto
1b Hidden W95 FAT3 75 PC/IX bb Boot Wizard hid fe LANstep
1c Hidden W95 FAT3 80 Old Minix be Solaris boot ff BBT
1e Hidden W95 FAT1
Hex code (type L to list codes): <-- 83
Command (m for help): <-- w
The partition table has been altered!
Calling ioctl() to re-read partition table.
Syncing disks.
root@server1:~#
Afterwards, there should be the partition /dev/sdb1:
fdisk -l
root@server1:~# fdisk -l
Disk /dev/sda: 32.2 GB, 32212254720 bytes
255 heads, 63 sectors/track, 3916 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00029d5c
Device Boot Start End Blocks Id System
/dev/sda1 * 1 3793 30461952 83 Linux
/dev/sda2 3793 3917 992257 5 Extended
/dev/sda5 3793 3917 992256 82 Linux swap / Solaris
Disk /dev/sdb: 32.2 GB, 32212254720 bytes
255 heads, 63 sectors/track, 3916 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x31e0dc4b
Device Boot Start End Blocks Id System
/dev/sdb1 1 3916 31455238+ 83 Linux
root@server1:~#
Let's format it with ext4...
mkfs.ext4 /dev/sdb1
... and mount it to /mnt/sdb1:
mkdir /mnt/sdb1
mount /dev/sdb1 /mnt/sdb1
You should see /dev/sdb1 in the output of...
mount
... now:
root@server1:~# mount
/dev/sda1 on / type ext3 (rw,errors=remount-ro)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,mode=0755)
proc on /proc type proc (rw,noexec,nosuid,nodev)
sysfs on /sys type sysfs (rw,noexec,nosuid,nodev)
udev on /dev type tmpfs (rw,mode=0755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=620)
/dev/sdb1 on /mnt/sdb1 type ext4 (rw)
root@server1:~#
To have /dev/sdb1 mounted automatically at boot time, add it to /etc/fstab:
vi /etc/fstab
[...] /dev/sdb1 /mnt/sdb1 ext4 errors=remount-ro 0 1 |
3 Preparing The Container
Container:
As we want to move /var/lib/mysql to the new partition, we need to stop MySQL first, make sure it isn't started automatically when the container is started, create a backup of /var/lib/mysql and a new, empty /var/lib/mysql directory:
/etc/init.d/mysql stop
update-rc.d -f mysql remove
mv /var/lib/mysql/ /var/lib/mysql_bak
mkdir /var/lib/mysql
chown mysql:mysql /var/lib/mysql
chmod 700 /var/lib/mysql
4 Creating A Bind Mount Script For The Container On The Host
Host:
On the host we now create the bind mount script /etc/vz/conf/101.mount (make sure you replace 101 with the correct container ID!) as follows:
vi /etc/vz/conf/101.mount
#!/bin/bash
. /etc/vz/vz.conf
. ${VE_CONFFILE}
SRC=/mnt/sdb1
DST=/var/lib/mysql
if [ ! -e ${VE_ROOT}${DST} ]; then mkdir -p ${VE_ROOT}${DST}; fi
mount -n -t simfs ${SRC} ${VE_ROOT}${DST} -o ${SRC}
|
You must adjust the SRC and DST variables to your needs. SRC is the directory which we want to mount in the container (/mnt/sdb1 in this example), and DST is the mount point in the container.
If you want to add mount options like noatime, you can add the -o switch to the mount line, e.g. as follows:
#!/bin/bash
. /etc/vz/vz.conf
. ${VE_CONFFILE}
SRC=/mnt/sdb1
DST=/var/lib/mysql
if [ ! -e ${VE_ROOT}${DST} ]; then mkdir -p ${VE_ROOT}${DST}; fi
mount -o noatime -n -t simfs ${SRC} ${VE_ROOT}${DST} -o ${SRC}
|
Make the script executable...
chmod +x /etc/vz/conf/101.mount
... and restart the container (that's why we disabled MySQL's system startup links for the container in chapter three - /var/lib/mysql is empty right now which will result in MySQL errors):
vzctl restart 101
5 Using The Bind Mount In The Container
Container:
After the container restart is finished, you can log into the container and check if the new mount exists:
mount
root@test:~# mount
/dev/simfs on / type simfs (rw,relatime)
/dev/simfs on /var/lib/mysql type simfs (rw,relatime)
proc on /proc type proc (rw,relatime)
sysfs on /sys type sysfs (rw,relatime)
tmpfs on /lib/init/rw type tmpfs (rw,nosuid,relatime,mode=755)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev,relatime)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620)
root@test:~#
df -h
root@test:~# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/simfs 1.0G 381M 644M 38% /
/dev/simfs 30G 172M 28G 1% /var/lib/mysql
tmpfs 128M 0 128M 0% /lib/init/rw
tmpfs 128M 0 128M 0% /dev/shm
root@test:~#
Go to the /var/lib directory:
cd /var/lib
ls -la
root@test:/var/lib# ls -la
total 72
drwxr-xr-x 18 root root 4096 Jul 17 10:25 .
drwxr-xr-x 13 root root 4096 Feb 13 2011 ..
drwxr-xr-x 5 root root 4096 Jul 17 10:16 apt
drwxr-xr-x 2 root root 4096 Oct 16 2010 aptitude
drwxr-xr-x 2 root root 4096 Feb 13 2011 dhcp
drwxr-xr-x 7 root root 4096 Jul 17 10:16 dpkg
drwxr-xr-x 2 root root 4096 Jan 1 2011 initscripts
drwxr-xr-x 2 root root 4096 Jan 1 2011 insserv
drwxrwsr-x 2 libuuid libuuid 4096 Feb 13 2011 libuuid
drwxr-xr-x 2 root root 4096 Apr 17 2010 logrotate
drwxr-xr-x 2 root root 4096 Dec 14 2010 misc
drwxr-xr-x 4 root root 4096 Jul 17 10:53 mysql
drwx------ 3 mysql mysql 4096 Jul 17 10:24 mysql_bak
drwxr-xr-x 2 root root 4096 Feb 13 2011 pam
drwxr-xr-x 2 root root 4096 Jul 17 10:23 quota
drwxr-xr-x 2 root root 4096 Jul 17 10:52 update-rc.d
drwxr-xr-x 2 root root 4096 Jul 17 10:53 urandom
drwxr-xr-x 3 root root 4096 Feb 13 2011 vim
root@test:/var/lib#
As you see, the new /var/lib/mysql directory has wrong permissions/ownership - let's correct that (the new permissions/ownership should be kept even after a restart of the container):
chown mysql:mysql /var/lib/mysql
chmod 700 /var/lib/mysql
Now let's move the databases from our backup back to /var/lib/mysql:
cp -pfr /var/lib/mysql_bak/* /var/lib/mysql
Then start MySQL:
/etc/init.d/mysql start
That's it! One last thing you should do is recreate MySQL's system startup links so that it starts automatically when the container is started:
update-rc.d mysql defaults
6 Links
- OpenVZ: http://openvz.org/
