3. Installing files

3. Installing files
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After a FileInstall object is instantiated, repeatedly invoking its addEntry method defines the files to be installed. Each call to addEntry defines a single file to install (or uninstall). addEntry takes the following parameters:

An std::ofstream object

This parameter should be a reference to an empty, unopened, std::ofstream object. If this call to addEntry defines a regular file (as defined by type), addEntry will open this file object for writing. The caller is responsible for writing the contents of the regular file into the std::ofstream object, and closing it.

type

The type of the file being installed. The possible types are:

F: A regular file.
Ca,b: A character device, major device number a, minor device b.
Ba,b: A block device, major device number a, minor device b.
I: A FIFO file.
S: A socket file.
L: A symbolic link.
D: A directory.
d: Delete an existing file. This file type indicates that an existing file should be removed.

Most file types (where it makes sense to do so) may also be followed by a “b”, which marks a configuration file that might need backing up. Configuration files are marked for special processing. When uninstalling a package (which happens as part of a regular uninstall, or an upgrade to a newer version of the package) LPMtool checks if the contents of the file were changed. LPMtool keeps track of checksums of all installed files, and it checksums the file again before removing it. If the checksum is different, the file is not removed, but renamed as “filename.lpmsave.YYYYMMDD-HHMMSS”.

File types may also be followed by “n” to indicate that if the file already exists, it should not be overwritten, instead it's the new file that should get renamed.

username

The file's owner.

groupname

The file's group.

mode

The file's permissions.

filename

The full pathname to the file.

symlinktarget

If the file is a soft link, this is the soft link's target.

hardLinkedTo

If this is not an empty string, this indicates that the file is a hard link to an existing file.

Note

All other parameters to addEntry must still be properly set even if hardLinkedTo is not an empty string. If hardLinkedTo is not located on the same partition as filename, or if it's not a regular file, LPMtool will ignore hardLinkedTo and install the file as if hardLinkedTo was an empty string. If the file is a regular file its contents will be automatically copied by addEntry.

addEntry performs the following actions:

If the previous call to addEntry opened a temporary file, addEntry expects that temporary file to be closed by now, so its buffers are flushed to disk (by using the sync(2) function).
The mount point of the partition that contains filename is identified.
In most cases addEntry creates a new file in $MOUNTPOINT/.lpm, and this file eventually becomes the file that's actually installed. $MOUNTPOINT/.lpm is a temporary directory where files are created, before they are installed in their final location. addEntry uses a counter to create a new filename for the new file in $MOUNTPOINT/.lpm.
If type is not “d”, hardLinkedTo is not empty, that file exists and it's a regular file on the same filesystem as filename, then $MOUNTPOINT/.lpm/COUNTER is hard linked to the existing file, and its buffers are flushed to disk.
If type is not “d”, hardLinkedTo is not empty, that file exists and it's a regular file on a different filesystem, then the contents of filename are copied to the new $MOUNTPOINT/.lpm/COUNTER, and its buffers are flushed.
In all other cases (except if the file type is “d”) $MOUNTPOINT/.lpm/COUNTER is created according to its filetype. If it's a regular file, then the first argument to addEntry(), std::ofstream, is opened accordingly. Otherwise $MOUNTPOINT/.lpm's buffers are flushed after the temporary file is created.
The file /.lpm/manifest is created, if it does not exist. The file's type, its temporary name (COUNTER), username, groupname, mode, and filename are appended to that file.
addEntry() returns the absolute pathname to the temporary file, MOUNTPOINT/.lpm/COUNTER, unless type is “d” (in which case addEntry() returns an empty string).

Package install/uninstall scripts (see Section 8, “Install/uninstall scripts”) are added by the addScript function. This function is a wrapper for addEntry that passes the value s for the type parameter, which addEntry handles just like “F” (plain file). addEntry creates a new file, whose contents become the install/uninstall script to run. The first line of the file will be “#!interpreter” (see Section 8, “Install/uninstall scripts” for more information).

The FileInstall objects also provide a set of functions that commit new records to a GDBM file. These functions are invoked by gdbm::ResourceDB's commit() function. These functions end up writing special records to /.lpm/manifest. Normally, each line in the manifest file names a single file to install (or uninstall). Four special records may also appear in this file, that correspond directly to the same functions:

Open a GDBM file.
Store a record in the GDBM file, with the given key.
Remove a record from the GDBM file, with the given key.
Close the GDBM file.

An open record must be followed by zero or more store/remove records, followed by a close record. No other records may appear after the open record, and before the close record. This is enforced naturally. gdbm::ResourceDB's commit() function calls the open method, the insert/remove methods, and the close methods, in one shot, before returning.

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