System Management Guide:
Operating System and Devices

File Systems Maintenance Tasks

The simplest tasks you might need when maintaining file systems are grouped within the following table. Instructions for additional maintenance tasks are located later in this section or in How-To's for System Management Tasks.

1. For options, see the command description in AIX 5L Version 5.2 Commands Reference.
2. Do not change the names of system-critical file systems, which are / (root) on logical volume 4 (hd4), /usr on hd2, /var on hd9var, /tmp on hd3, and /blv on hd5. If you use the hdn convention, start at hd10.
3. Check the file systems before mounting by using the procedure Verify File Systems or running the fsck command.
4. If an unmount fails, it might be because a user or process has an opened file in the file system being unmounted. The fuser command lets you find out which user or process might be causing the failure.
5. A file system group is a collection of file systems which have the same value for the type= identifier in the /etc/filesystems file.

Recover One or More Files from an Online JFS2 Snapshot

When a file becomes corrupted, you can replace it if you have an accurate copy in an online JFS2 snapshot. Use the following procedure to recover one or more files from a JFS2 snapshot image:

1. Mount the snapshot. For example:

   mount -v jfs2 -o snapshot /dev/mysnaplv /home/aaa/mysnap

2. Change to the directory that contains the snapshot. For example:

   cd /home/aaa/mysnap

3. Copy the accurate file to overwrite the corrupted one. For example:

   cp myfile /home/aaa/myfs

   copies only the file named myfile. The following example copies all files at once:

   cp -R home/aaa/mysnap /home/aaa/myfs

   For more examples, see the cp or cpio command descriptions in the AIX 5L Version 5.2 Commands Reference.

Use File Systems on CD-ROM and DVD Disks

Beginning with AIX 5.2, CDs and DVDs are automatically mounted by default but this feature can be disabled. If the feature has been disabled, use the cdmount command to mount the CDRFS or UDFS file system, for example:

cdmount cd0

When a DVD is automounted, the UDFS file system is read-only by default. If you want the automount feature or the cdmount command to automatically mount a read/write UDFS, edit the cdromd.conf file. You can also manually mount a read/write UDFS with the following command:

mount -V udfs DevName MtPt

Where DevName is the name of the DVD drive and MtPt is the mount point for the file system.

Use File Systems on Read/Write Optical Media

The following types of file systems can be used on read/write optical media:

• CDRFS
• JFS

A CD-ROM file system (CDRFS) can be stored on read/write optical media, provided that the optical media is write-protected, as well as on a CD-ROM. The following table tells you how to add, mount, or unmount a CDRFS on read/write optical media. You must specify the following information when mounting the file system:

1. Make sure the read/write optical media is write-protected.
2. A CDRFS file system must be unmounted before the read/write optical media can be removed.

A JFS provides a read/write file system on optical media similar to those on a hard disk. You must have system authority to create or import a read/write file system on read/write optical media (that is, your login must belong to the system group) and you must have the following information:

Volume group name

Specifies the name of the volume group

Device name

Specifies the logical name of the read/write optical drive

Mount point

Specifies the directories where the file systems will be mounted

Automatic mount

Specifies whether the file system will be mounted automatically at system restart

1. Any volume group created on read/write optical media must be self contained on that media. Volume groups cannot go beyond one read/write optical disk.
2. When accessing a previously created journaled file system, the volume group name does not need to match the one used when the volume group was created.

1. This procedure is required whenever inserting media containing journaled file systems.
2. Removing a journaled file system destroys all data contained in that file system and on the read/write optical media.

Verify File Systems

Inconsistencies can occur in file systems when the system is stopped while file systems remained mounted or when a disk is damaged. In such circumstances, it is important to verify file systems before mounting them. Also verify your file systems in the following circumstances:

• After a malfunction; for example, if a user cannot change directories to a directory that has that user's permissions (uid)
• Before backing up file systems to prevent errors and possible restoration problems
• At installation or system boot to make sure that there are no operating system file errors

Check a User-Defined File System

1. Unmount the user-defined file system being checked.
2. Ensure you have write permission on files in the file system. Otherwise, the fsck cannot repair damaged files even if you answer Yes to repair prompts.
3. Use the smit fsck fast path to access the Verify a File System menu.
4. Do one of the following:
   1. Specify the name of an individual file system to check in the NAME of file system field, or
   2. Select a general file system type to check, such as a journaled file system (JFS) in the TYPE of file system field.
5. If you want to limit your check to the most likely candidates, specify Yes in the FAST check? field. The fast-check option checks only those file systems that are likely to have inconsistencies such as the file systems that were mounted when the system stopped at some point in the past.
6. Specify the name of a temporary file on a file system not being checked in the SCRATCH file field.
7. Start the file system check.

Check Root and /usr File Systems

To run the fsck command on / or /usr file system, you must shut down the system and reboot it from removable media because the / (root) and /usr file systems cannot be unmounted from a running system. The following procedure describes how to run fsck on the / and /usr file systems from the maintenance shell.

1. With root authority, shut down your system.
2. Boot from your installation media.
3. From the Welcome menu, choose the Maintenance option.
4. From the Maintenance menu, choose the option to access a volume group.
5. Choose the rootvg volume group. A list of logical volumes that belong to the volume group you selected is displayed.
6. Choose 2 to access the volume group and to start a shell before mounting file systems.

   In the following steps, you will run the fsck command using the appropriate options and file system device names. The fsck command checks the file system consistency and interactively repairs the file system. The / (root) file system device is /dev/hd4 and the /usr file system device is /dev/hd2.

7. To check / file system, type the following:

   $ fsck -y /dev/hd4

   The -y flag is recommended for less experienced users (see the fsck command).

8. To check the /usr file system, type the following:

   $ fsck -y /dev/hd2

9. To check other file systems in the rootvg, type the fsck command with the appropriate device names. The device for /tmp is /dev/hd3, and the device for /var is /dev/hd9var.
10. When you have completed checking the file systems, reboot the system.