OpenStack云主机如何在线动态扩展根目录

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一、背景

一般云主机的根目录都是在镜像制作时就确定下来了，在启动云主机时，选定的实例类型也会限定云主机的/目录大小。 偶尔可能会出现系统/目录不够用的情况，一般有两种方式来解决这个问题： 第一个是添加磁盘，将相关文件移至新增盘； 第二个是扩展/目录。

二、云主机启动的两种方式

云主机启动时也有两种方式

2.1. 方式一、从卷启动

这种方式启动的云主机，指定的卷大小必须不小于镜像的根目录大小，比如镜像的/目录大小为50G，此处指定为100G，但是云主机启动之后/目录还是为50G，这样就可以直接将这剩余的50G扩展到/目录下。这样做有个限制，扩展的大小有上限，取决于云主机创建时指定的大小。参考方式二，可以跨过这个限制。

查看分区情况

# lsblk NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTvda             252:0    0  100G  0 disk ├─vda1          252:1    0    1G  0 part /boot└─vda2          252:2    0   49G  0 part   └─centos-root 253:0    0   49G  0 lvm  /

将剩余空间分区

# fdisk /dev/vdaCommand (m for help): nPartition type:   p   primary (2 primary, 0 extended, 2 free)   e   extendedSelect (default p): pPartition number (3,4, default 3): First sector (104857600-209715199, default 104857600): Using default value 104857600Last sector, +sectors or +size{K,M,G} (104857600-209715199, default 209715199): Using default value 209715199Partition 3 of type Linux and of size 50 GiB is setCommand (m for help): wThe partition table has been altered!Calling ioctl() to re-read partition table.WARNING: Re-reading the partition table failed with error 16: Device or resource busy.The kernel still uses the old table. The new table will be used atthe next reboot or after you run partprobe(8) or kpartx(8)Syncing disks.# lsblk NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTvda             252:0    0  100G  0 disk ├─vda1          252:1    0    1G  0 part /boot└─vda2          252:2    0   49G  0 part   └─centos-root 253:0    0   49G  0 lvm  /# partprobe# lsblk    NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTvda             252:0    0  100G  0 disk ├─vda1          252:1    0    1G  0 part /boot├─vda2          252:2    0   49G  0 part │ └─centos-root 253:0    0   49G  0 lvm  /└─vda3          252:3    0   50G  0 part

创建PV

# pvcreate /dev/vda3  Physical volume "/dev/vda3" successfully created.

添加物理卷

# vgscan   Reading volume groups from cache.  Found volume group "centos" using metadata type lvm2# vgextend centos /dev/vda3  Volume group "centos" successfully extended

扩展物理卷

# df -hFilesystem               Size  Used Avail Use% Mounted on/dev/mapper/centos-root   49G  1.6G   48G   4% /devtmpfs                 1.9G     0  1.9G   0% /devtmpfs                    1.9G     0  1.9G   0% /dev/shmtmpfs                    1.9G  8.5M  1.9G   1% /runtmpfs                    1.9G     0  1.9G   0% /sys/fs/cgroup/dev/vda1               1014M  145M  870M  15% /boottmpfs                    379M     0  379M   0% /run/user/0# lvextend -l +100%FREE /dev/mapper/centos-root  Size of logical volume centos/root changed from <49.00 GiB (12543 extents) to 98.99 GiB (25342 extents).  Logical volume centos/root successfully resized.# lsblk NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTvda             252:0    0  100G  0 disk ├─vda1          252:1    0    1G  0 part /boot├─vda2          252:2    0   49G  0 part │ └─centos-root 253:0    0   99G  0 lvm  /└─vda3          252:3    0   50G  0 part   └─centos-root 253:0    0   99G  0 lvm  /# df -hFilesystem               Size  Used Avail Use% Mounted on/dev/mapper/centos-root   49G  1.6G   48G   4% /devtmpfs                 1.9G     0  1.9G   0% /devtmpfs                    1.9G     0  1.9G   0% /dev/shmtmpfs                    1.9G  8.5M  1.9G   1% /runtmpfs                    1.9G     0  1.9G   0% /sys/fs/cgroup/dev/vda1               1014M  145M  870M  15% /boottmpfs                    379M     0  379M   0% /run/user/0

xfs在线扩容

# xfs_growfs /dev/mapper/centos-rootmeta-data=/dev/mapper/centos-root isize=512    agcount=4, agsize=3211008 blks         =                       sectsz=512   attr=2, projid32bit=1         =                       crc=1        finobt=0 spinodes=0data     =                       bsize=4096   blocks=12844032, imaxpct=25         =                       sunit=0      swidth=0 blksnaming   =version 2              bsize=4096   ascii-ci=0 ftype=1log      =internal               bsize=4096   blocks=6271, version=2         =                       sectsz=512   sunit=0 blks, lazy-count=1realtime =none                   extsz=4096   blocks=0, rtextents=0data blocks changed from 12844032 to 25950208

扩展成功，重启云主机后/目录依旧为扩展后大小

# df -hFilesystem               Size  Used Avail Use% Mounted on/dev/mapper/centos-root   99G  1.6G   98G   2% /devtmpfs                 1.9G     0  1.9G   0% /devtmpfs                    1.9G     0  1.9G   0% /dev/shmtmpfs                    1.9G  8.5M  1.9G   1% /runtmpfs                    1.9G     0  1.9G   0% /sys/fs/cgroup/dev/vda1               1014M  145M  870M  15% /boottmpfs                    379M     0  379M   0% /run/user/0

2.2. 方式二、从镜像启动

直接从镜像启动，不创建卷，云主机启动后/目录的大小为镜像中默认大小,这样就得新增一块盘，直接将这块盘扩展到/目录即可

# lsblk NAME            MAJ:MIN RM SIZE RO TYPE MOUNTPOINTvda             252:0    0  50G  0 disk ├─vda1          252:1    0   1G  0 part /boot└─vda2          252:2    0  49G  0 part   └─centos-root 253:0    0  49G  0 lvm  /# lsblk NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTvda             252:0    0   50G  0 disk ├─vda1          252:1    0    1G  0 part /boot└─vda2          252:2    0   49G  0 part   └─centos-root 253:0    0   49G  0 lvm  /vdb             252:16   0  100G  0 disk # fdisk /dev/vdbWelcome to fdisk (util-linux 2.23.2).Changes will remain in memory only, until you decide to write them.Be careful before using the write command.Device does not contain a recognized partition tableBuilding a new DOS disklabel with disk identifier 0x5ee47290.Command (m for help): nPartition type:   p   primary (0 primary, 0 extended, 4 free)   e   extendedSelect (default p): pPartition number (1-4, default 1): First sector (2048-209715199, default 2048): Using default value 2048Last sector, +sectors or +size{K,M,G} (2048-209715199, default 209715199): Using default value 209715199Partition 1 of type Linux and of size 100 GiB is setCommand (m for help): wThe partition table has been altered!Calling ioctl() to re-read partition table.Syncing disks.# lsblk          NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTvda             252:0    0   50G  0 disk ├─vda1          252:1    0    1G  0 part /boot└─vda2          252:2    0   49G  0 part   └─centos-root 253:0    0   49G  0 lvm  /vdb             252:16   0  100G  0 disk └─vdb1          252:17   0  100G  0 part # df -hFilesystem               Size  Used Avail Use% Mounted on/dev/mapper/centos-root   49G  1.6G   48G   4% /devtmpfs                 1.9G     0  1.9G   0% /devtmpfs                    1.9G     0  1.9G   0% /dev/shmtmpfs                    1.9G  8.5M  1.9G   1% /runtmpfs                    1.9G     0  1.9G   0% /sys/fs/cgroup/dev/vda1               1014M  145M  870M  15% /boottmpfs                    379M     0  379M   0% /run/user/0# pvcreate /dev/vdb1  Physical volume "/dev/vdb1" successfully created.# vgscan   Reading volume groups from cache.  Found volume group "centos" using metadata type lvm2# df -hFilesystem               Size  Used Avail Use% Mounted on/dev/mapper/centos-root   49G  1.6G   48G   4% /devtmpfs                 1.9G     0  1.9G   0% /devtmpfs                    1.9G     0  1.9G   0% /dev/shmtmpfs                    1.9G  8.5M  1.9G   1% /runtmpfs                    1.9G     0  1.9G   0% /sys/fs/cgroup/dev/vda1               1014M  145M  870M  15% /boottmpfs                    379M     0  379M   0% /run/user/0# vgextend centos /dev/vdb1    Volume group "centos" successfully extended# lvextend -l +100%FREE /dev/mapper/centos-root  Size of logical volume centos/root changed from <49.00 GiB (12543 extents) to 148.99 GiB (38142 extents).  Logical volume centos/root successfully resized.# xfs_growfs /dev/mapper/centos-rootmeta-data=/dev/mapper/centos-root isize=512    agcount=4, agsize=3211008 blks         =                       sectsz=512   attr=2, projid32bit=1         =                       crc=1        finobt=0 spinodes=0data     =                       bsize=4096   blocks=12844032, imaxpct=25         =                       sunit=0      swidth=0 blksnaming   =version 2              bsize=4096   ascii-ci=0 ftype=1log      =internal               bsize=4096   blocks=6271, version=2         =                       sectsz=512   sunit=0 blks, lazy-count=1realtime =none                   extsz=4096   blocks=0, rtextents=0data blocks changed from 12844032 to 39057408# df -hFilesystem               Size  Used Avail Use% Mounted on/dev/mapper/centos-root  149G  1.6G  148G   2% /devtmpfs                 1.9G     0  1.9G   0% /devtmpfs                    1.9G     0  1.9G   0% /dev/shmtmpfs                    1.9G  8.5M  1.9G   1% /runtmpfs                    1.9G     0  1.9G   0% /sys/fs/cgroup/dev/vda1               1014M  145M  870M  15% /boottmpfs                    379M     0  379M   0% /run/user/0# lsblk NAME            MAJ:MIN RM  SIZE RO TYPE MOUNTPOINTvda             252:0    0   50G  0 disk ├─vda1          252:1    0    1G  0 part /boot└─vda2          252:2    0   49G  0 part   └─centos-root 253:0    0  149G  0 lvm  /vdb             252:16   0  100G  0 disk └─vdb1          252:17   0  100G  0 part   └─centos-root 253:0    0  149G  0 lvm  /

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