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Verifying and setting file permissions


Non-root users performing installation and subsequent installation operations (SIOs) on the appserver product can verify whether they have the correct permissions to ensure that the installation operation can be completed successfully, without failure due to file permission errors. In addition to the function which verifies file permissions, we can set the ownership and permissions (with limitations) on all installed files.

SIOs include operations such as feature installations, edition upgrades, maintenance installations (such as fix packs or refresh packs), feature pack installations, and slip installations of custom installation packages (CIPs) created with IBM WebSphere Installation Factory. We can change file ownership and permissions after installation using the chutils command.

(Windows) Restriction: The verify and set permissions features are not currently available on Windows operating systems.

 

Verifying file permissions

When an appserver installation is initially performed, the resulting installation is owned by a single user and group. Certain SIOs can be performed by another user whether the user is root or non-root.

Use the verify permissions utility to determine whether a subsequent installation operation would fail due to insufficient file permissions. We can run this check as an optional function in the standard application server installer, CIPs, and the Update Installer. If the check fails, the installation operation is prevented until the error has been resolved. The installation operation is prevented in order to avoid corruption of installations caused by an incomplete subsequent installation operation. Without a successful installation permissions check, an unexpected file permission error could occur. This would cause the installation to fail and leave WAS in an indeterminate state.

The verify permissions utility is available in the installation wizard as a check box on the installation summary panel before you begin the actual installation process, or if we are installing silently, then we can run the utility by uncommenting the -OPT checkFilePermissions="true" option in the response file.

During the verify permissions check, the installer does not create or modify any product files. The permissions check only confirms whether the file operations would succeed based on file ownership and permissions. The target location is not modified as a result, and no configuration actions are run.

If the verify permissions check fails, then all file permission problems that occur during the simulation are written to a log in the user's home directory. Entries in the log files will indicate which files are not writable by the current user including file names, file operations, and specific permission issues. We can address file permission errors and rerun the verify permissions utility without exiting the installation wizard. The log file is located in...

<user_home>/waslogs/log.txt

 

Set file ownership and permissions with the chutils command

Use the chutils command to set the file ownership and permissions for an entire installation to an owner or group that differs from the user that performed the initial installation. The main benefit is the ability to have the initial install performed by one user and then have different users perform supported SIOs. The chutils command is located in the APP_ROOT/instutils directory. The command can be used for the following:

The command can edit the following ownership and permissions:


Table 1. chutils command options and descriptions

Option Description
-installlocation=<install_home> Optional. The absolute path to the installation root directory. Defaults to the current install location, or APP_ROOT.
-setowner=<username> Sets the owner for each file and directory.
-setgroup=<groupname> Sets the group for each file and directory.
-setmod=[reset]|[grp2owner] Sets the permissions on the files and directories.

  • reset - Resets the owner, group and other permissions to the default values.

  • grp2owner - Sets the group's permission to match the owner's permissions.

-help Display the permission utility's help.
-debug Displays additional runtime information.

Considerations and limitations:

  1. chutils is intended to be run by root.

  2. chutils can be run with multiple options at once.

  3. Cannot modify permissions for parent directories of APP_ROOT. For example, if APP_ROOT is in User A's home directory, and the root user uses chutils to change the ownership of APP_ROOT to User B, then APP_ROOT might still be inaccessible to User B since it is still a subdirectory of User A's home directory.

  4. Cannot modify permissions for owner or world, although group permissions can be elevated to match owner permissions.

 

Troubleshooting




 

Related concepts


Non-root installation