Moduel 4 Performing Mounts and Umounts
Note – While system administrators typically use the /usr/sbin/mount
command, the system boot scripts use the /sbin/mount command.
介紹/etc/vfstab文件:
/etc/vfstab列出系統啟動時自動mount的文件, 除/etc/mnttab和/var/run之外;
/etc/vfstab文件分出七個區域:
device to mount 被mount的設備和偽設備
device to fsck The raw or character device e.g. /dev/rdsk下的
對于偽設備如:/proc 或 fd 這項可寫 -
mount point mount 的路徑
FS type 文件系統類型
fsck pass 指示在系統啟動時是否fsck檢測;0不檢1表示fsck為系統正常啟動運行
大于1時表示把此設備加入fsck運行列表,fsck可同時檢測8個設備,
mountall命令忽略此項
mount at boot yes 要求啟動時自動mount,no 則不
Note – For / (root), /usr, and /var (if it is a separate file system) file
systems, the mount at boot field value is specified as no. The kernel
mounts these file systems as part of the boot sequence before the
mountall command is run. The mount command explicitly mounts the
file systems / (root) and /usr as specified in the
/etc/rcS.d/S30rootusr.sh script and the /var file system as specified
in the /etc/rcS.d/S70buildmnttab script.
mount options A comma-separated list of options passed to the
mount command. A dash (-) indicates the use of
default mount options.
介紹/etc/mnttab文件:
此文件是一個只讀文件,當mount一項時,會在此文件中入一條,umount后也會在此文件中刪除相應項;
包括五項區域:
mount point 掛接點
Device Name 設備名,塊設備是文件系統的物理名稱;
Mount Options 文件系統上生效的掛載選項列表
dev=number 主從設備號
Date and time mounted mount的日期時間
使用mount
mount /dev/dsk/c#d#t#s# /mountpoint
不加參數時,使用以下默認屬性:
read/write Indicates whether reads and writes are allowed on
the file system.
setuid Permits the execution of setuid programs in the
file system.
intr/nointr Allows and forbids keyboard interrupts to kill a
process that is waiting for an operation on a locked
file system.
nologging Indicates that logging is not enabled for the ufs file
system.
largefiles Allows for the creation of files larger than 2 Gbytes.
A file system mounted with this option can contain
files larger than 2 Gbytes.
xattr Supports extended attributes not found in
standard UNIX attributes.
onerror=action Specifies the action that the ufs file system should
take to recover from an internal inconsistency on a
file system. An action can be specified as:
panic—Causes a forced system shutdown. This is
the default.
lock — Applies a file system lock to the file
system.
umount — Forcibly unmounts the file system.
------------------------------------------------------------------------------
Note – Due to file system overhead, the largest file size that can be created
is approximately 866 Gbytes.
------------------------------------------------------------------------------
使用mount命令的option
Some options used to mount local file systems include: ro, nosetuid,
noatime, nolargefiles, and logging.
格式: mount -o option,option,... device_name mount_point
# mount -o ro /dev/dsk/c0t0d0s6 /usr -------設成只讀
下面是使用多個參數,設成只讀以及不允許執行setuid進程,但并不限制生成setuid
# mount -o ro,nosuid /dev/dsk/c0t0d0s7 /export/home
為提高磁盤訪問性能,文件系統訪問頻繁,最后訪問時間并不計較的可以
# mount -o noatime /dev/dsk/c0t0d0s7 /export/home
防止成生超過2G的文件,
# mount -o nolargefiles /dev/dsk/c0t0d0s7 /export/home
如果文件系統已經存在超過2G的大文件,mount會挫敗,如果想成功mount,則必須刪除相關大文件,
并且刪除后必須用fsck來更新超級塊的信息,如果一次運行fsck還不能成功mount則必須用fsck
來清除超級塊的信息;
使UFS文件系統寫日志;
# mount -o logging /dev/dsk/c0t0d0s7 /export/home
存放日志文件的大小,大約是每1G分配1M的大小,最大不超過64M字節;
當UFS日志達其最大時，它就開始將事務記錄到文件系統中。文件系統被卸載時，整個UFS日志
都被清空，所有事務都被寫入文件系統。
UFS日志有兩個好處。一，它文件系統的不一致性，也就不再需要長時間運行fsck掃描。
二，可以跳過fsck掃描，這就減少了系統在被以非正常的關閉方法關閉時，重啟的時間，
使用mountall命令:
mountall -l 只mount本地的所有文件系統;
mountall命令讀取/etc/vfstab文件內容,當device to fsck 項大于0時,fsck會檢測文件系統是否完好,以致于安全掛接.當系統文件壞掉,fsck會試圖修復,mountall會mount其它掛接點,和device to fsck 項等于0的掛接點.
mount一個新的文件系統:
八步:
1.把硬盤放入服務器,
2.重啟或devfsadm讓系統識別硬盤;
3.format把硬盤分區;
4.newfs在磁盤slice上生成新的文件系統;
5.在/目錄下用mkdir 生成一個新的掛接點;
6.mount文件系統到掛接點;
7.用mount命令查看是否mount成功;
8.修改/etc/vfstab文件,讓系統下次重啟時自動加載;
mount不同類型的文件系統:
如果mount時沒有以mount -F fstype指明的話,mount會以ufs來作為默認的類型,mount根據設備名, 塊名,或掛接點來判斷文件類型;
mount 不能從/etc/vfstab的fs entry來判斷,會以/etc/default/fs file 或
/etc/dfs/fstypes來決定文件的掛接類型,如果是本地文件系統則是/etc/default/fs 文件中一行
LOCAL=ufs 來確定掛接類型;
如果是遠程文件系統,則從/etc/dfs/fstypes第一行來確定
nfs NFS Utilities
autofs AUTOFS Utilities
cachefs CACHEFS Utilities
Using the fstyp Command來查看文件類型:
# fstyp /dev/rdsk/c0t0d0s7
ufs
指定一下hsfs文件系統:
當volume manage停止時,用hsfs來指定一個cdrom
# mount -F hsfs -o ro /dev/dsk/c0t6d0s0 /cdrom
指定一個pcfs文件系統:
當卷管理停止時,掛接一個駐留在diskette(軟盤)的文件系統
# mkdir /pcfs
# mount -F pcfs /dev/diskette /pcfs
執行umount命令:
提示:在umount文件系統前,都是先從/etc/mnttab文件種刪除相應行;
從掛接點刪除:
#umount /export/home
從邏輯硬件文件名刪除:
# umount /dev/dsk/c0t0d0s7
執行umountall命令:
/usr/sbin/umountall命令會在系統關閉或在命令輸入umountall時讀取/etc/mnttab文件,然后umount
vfstab文件中除/ (root), /usr, /proc, /dev/fd, /var,/var/run, and /tmp.之外所有行;
umount所有文件系統:
#umountall
umount所有本地的文件系統:
#umountall -l
umountall狀態為busy的系統:
以下四種情況,文件系統都會顯示:umount: file_system_name busy
1 A program is accessing a file or directory in the file system
2 A user is accessing a directory or file in the file system
3 A program has a file open in that file system
4 The file is being shared
有兩種方法解決:
(1) 使用fuser命令來確認掛接點有那些進程在訪問,然后殺掉
(2) 用umount -f 強制umount;
用fuser命令的四步:
1.確認掛接點有那些進程需要殺掉
#fuser -cu /mount_point
2.向進程發出SIGKILL信號:
#fuser -ck /mount_point
3.確認看是否還有進程在訪問掛接點
#fuser -c /mount_point
4.umount掛接點
#umount /mount_point
umount -f 丟失數據,僵死進程,但比較適合遠程共享時,遠程沒有響應.