我执行了以下程序以便将400m添加到交换中,
我从sdb磁盘拿走了400m ,交换量增加了
一切都很好,但在最后的命令之前,我表演了
mkswap /dev/rootvg/swap
我从mkswap获得以下警告消息
mkswap: /dev/rootvg/swap: warning: don't erase bootbits sectors on whole disk. Use -f to force. Setting up swapspace version 1, size = 2490364 KiB no label, UUID=2f42fa37-987d-40a5-8cf6-5707e1d8f077
最后,交换量达到预期的2.4G
但是我不担心mkswap命令的警告信息
请告知这个警告的含义是什么:
mkswap: /dev/rootvg/swap: warning: don't erase bootbits sectors on whole disk. Use -f to force.
如果这样可以吗?
我的程序在Linux redhat机器上 – 版本6
# swapon -s Filename Type Size Used Priority /dev/dm-1 partition 2064380 0 -1 # free total used free shared buffers cached Mem: 5991892 539036 5452856 212 70444 270664 -/+ buffers/cache: 197928 5793964 Swap: 2064380 0 2064380 # pvs PV VG Fmt Attr PSize PFree /dev/sdb rootvg lvm2 a--u 7.97g 416.00m /dev/sdc orahome lvm2 a--u 30.00g 15.00g # lsblk /dev/sdb NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT sdb 8:16 0 8G 0 disk |-rootvg-swap (dm-1) 253:1 0 2G 0 lvm [SWAP] |-rootvg-slash (dm-2) 253:2 0 576M 0 lvm / |-rootvg-usr (dm-3) 253:3 0 1.4G 0 lvm /usr |-rootvg-home (dm-4) 253:4 0 256M 0 lvm /home |-rootvg-opt (dm-5) 253:5 0 416M 0 lvm /opt `-rootvg-var (dm-6) 253:6 0 3G 0 lvm /var # swapon -s Filename Type Size Used Priority /dev/dm-1 partition 2064380 0 -1 # swapoff /dev/rootvg/swap # lvresize /dev/rootvg/swap -L +400m Rounding size to boundary between physical extents: 416.00 MiB. Size of logical volume rootvg/swap changed from 1.97 GiB (63 extents) to 2.38 GiB (76 extents). Logical volume swap successfully resized. # mkswap /dev/rootvg/swap mkswap: /dev/rootvg/swap: warning: don't erase bootbits sectors on whole disk. Use -f to force. Setting up swapspace version 1, size = 2490364 KiB no label, UUID=2f42fa37-987d-40a5-8cf6-5707e1d8f077 # swapon /dev/rootvg/swap # free total used free shared buffers cached Mem: 5991892 539680 5452212 212 70536 270892 -/+ buffers/cache: 198252 5793640 Swap: 2490364 0 2490364
看起来像一个安全预防措施,以防止您破坏引导扇区等…当您可能打算使用分区时使用整个磁盘。
这个警告信息不再存在于CentOS 6.5或Ubuntu 16.04中。
这个较老的(2006)mkswap.c模糊地定义了bootbits: http ://code.metager.de/source/xref/busybox/util-linux/mkswap.c
/* char bootbits[1024]; Space for disklabel etc. */
从CentOS 6.5 mkswap.c
:
if (is_whole_disk_fd(fd, devname)) { /* don't zap bootbits on whole disk -- we know nothing * about bootloaders on the device */ whole = 1; zap = 0;
我对C不是很了解,但新代码看起来更聪明,可能还保留了启动数据。 我没有深究。