The Filesystem Status File

default: vol = AIX mount = false check = false : dev = devhd4 vol = root mount = automatic check = true log = devhd8 ...etc. The purpose of the second file etcvfs is different. This is a generic file that defines filesystem types. Here is a self−explanatory example from the very same AIX system: cat etcvfs vfs 77 1.20 comcfgetcvfs, bos, bos320 this file describes the known virtual file system implementations. format: the name and vfs_number should match what is in sysvmount.h The standard helper directory is etchelpers Uncomment the following line to specify the local or remote default vfs. defaultvfs jfs nfs name vfs_number mount_helper fil sys_helper cdrfs 5 none none jfs 3 none sbin helpersv3fshelper nfs 2 sbinhelpers nfsmnthelp none remote

5.4.4 The Filesystem Status File

The filesystem configuration file defines the configuration that the system is trying to achieve. A configuration entry does not necessarily mean that the appropriate mount attempt will be successful; there are many reasons that can cause mounting to fail. For example, for all removable media, a mount attempt will fail if a volume was not loaded into the device floppy drive, CDROM drive, etc., not to mention a broken disk or corrupted filesystem. Even after a successful mounting, the filesystem could be automatically or manually dismounted. Briefly, the real filesystem status does not necessarily match with the configuration requirements. The system automatically maintains a separate table of its current filesystem status. This table is updated always when any filesystem is mounted or dismounted. The table is an ASCII readable file that can be manually modified; of course, manual modification is not recommended except as a last resort to fix an obvious error. Two file names are common for the filesystem status file: etcmnttab and etcmtab; both names reflect the files purpose as a mounted filesystem table. The filesystem status file contains a table of all filesystems currently mounted by the mount command. The umount command removes entries from this file. The file contains an entry a line of information for each mounted filesystem, which is structurally identical to the contents of the filesystem configuration file. The entry format varies slightly among UNIX flavors, just as the filesystem configuration entries do. A typical entry looks like: fsname dir type opts freq passno where 127 A mount−point directory type A filesystem type opts Are comma−separated filesystem options freq A number indicating backup strategy for the filesystem passno A number indicating the fsck order for the filesystem The content of the etcmtab file on SunOS is presented to illustrate the previous information: cat etcmtab devsd0a 4.2 rw,dev=0700 1 1 devsd0g usr 4.2 rw,dev=0706 1 2 devsd0h home 4.2 rw,dev=0707 1 3 indigo1:indigo1 indigo1 nfs rw,bg,intr,hard,dev= 8200 0 0 hcprophet:hcprophet hcprophet nfs rw,bg,hard,intr,dev= 8203 0 0 This is the filesystem status file for the same system for which the filesystem configuration file etcfstab was shown earlier. If we compare the two files, and assume the filesystems were mounted automatically during the system startup, we can conclude: All local filesystems are mounted. • The floppy diskette was not inserted at the startup time, so the pcfs filesystem is not mounted. • One of the nfs filesystems is not mounted, obviously because a connection with the remote host rs01−ch was not established at that time it is a logical to speculate that the remote host was not reachable, although there could be a number of other reasons for mounting to fail. •

5.5 A Few Other Filesystem Issues