Filer_Linux: Linux Filer Appliance

	At a Glance
	Catalog	Filer
	Category	Filers
	User volumes	yes
	Min. memory	128 MB
	OS	Linux
	Constraints	no

Functional overview

Filer_Linux is an appliance that provides filesystem-level access to a volume with a Linux file system. Filer_Linux supports the following Linux file systems: ext2, ext3, fat16, fat32, reiserfs, swap, and ext3-snapshot (ext3 over LVM with snapshots) and supports the following modes of operation:

• format: format the volume to the specified filesystem (e.g., execute mkfs)
• fscopy: perform a filesystem-level copy from one volume to another, the destination volume is formatted prior to the copy
• fsck: check the file system on the volume
• fsrepair: check and repair the file system on the volume
• manual: provide user-level access to the volume through both a Web GUI and root shell (through SSH)

In manual mode, Filer_Linux provides GUI access and root shell to the volume through its default interface. In this mode, Filer_Linux also optionally provides external network access in order for the user to copy files to and from the volume. Manual mode operation can be performed over one or two volumes.

The Filer appliances are used internally by AppLogic and should not be used in regular AppLogic applications.

Boundary

Resources

Terminals

The external interface is enabled. It is used for incoming and outgoing traffic and its network settings are configured through properties. It is only used in the manual mode and is not configured in all other modes.

The default interface is enabled. It is used for maintenance. Also, in the manual mode, it is used for accessing the Web GUI.

User Volumes

Properties

Operation modes

The following table lists the supported mode for each of the supported file systems:

In manual mode:

• for all file systems, but swap, the volume is mounted on /mnt/vol.
• for a swap volume, the block device is accessible on /dev/hda4.

Filesystem options

This section lists the file system options (as specified on fs_options) for each file system supported by Filer_Linux.

• ext2
  • None

• ext3
  • None

• fat16
  • None

• fat32
  • None

• reiserfs
  • None

• swap
  • None

• ext3-snapshot
  • vol_group_name: string, name of the LVM volume group to create on the dst volume. If empty, randomly generate a volume group name. Default: (empty).
  • data_percentage: integer, percentage of the volume that is used to store data, remaining portion of the volume is for snapshots. Default: 80 (80% of the volume is for data).

Interface

The Filer appliances provide an HTTP interface on their default interface in order to collect status on non-manual volume operations and to access the Web GUI when in manual mode. The following functions are available by URL:

• /: interactive access to the dst volume through the Web GUI, only available in manual mode
• /api/status: returns the status for the current volume operation, only available in non-manual mode
  • The format of the output is the following: [progress=W, ]poll=X, status=Y, errortxt=Z
    • progress: integer, 0..100, progress of the current operation. If progress cannot be reported, then the progress field is not returned. Progress is not reported for the following modes:
      • format for all file systems
      • fsck and fsrepair for all file systems, but ext2, ext3, ext3-snapshot, and ufssol
    • poll: integer, recommended status poll interval, in seconds.
    • status: integer, status of the volume operation. See below for the list of statuses that can be returned by Filer_Linux.
    • errortxt: string, error message, if an error occurred (e.g., non-zero status)
  • The following is the list of statuses that Filer_Linux can return in the status field for a specific volume operation:
    • 0 - success
    • 100 - operation failed
    • 101 - operation not supported
    • 102 - operation not implemented
    • 103 - operation canceled
    • 104 - I/O error
    • 200 - no space left on volume
    • 201 - file system errors detected
    • 300 - out of memory
    • 400 - pending

Web GUI

The Filer appliances use a web-based file manager named eXtplorer to provide the Web GUI access to a volume (accessible only in manual mode). eXtplorer is released under the GNU GENERAL PUBLIC LICENSE Version 2. The version of eXtplorer used in the filers have been modified. The following are the changes to eXtplorer:

1. Removed the login.
2. Updated eXtplorer not to display its own files.
3. Changed the file list to show the target for all links under the "Type" column.
4. Changed the tooltip generated when the mouse is over a directory in the directory list to show the symlink target if the directory is a symlink.
5. Changed symlink creation through the GUI to support orphaned links.
6. Changed delete file through the GUI to support deletion of symlinks.
7. Added an interface for editing the volume base path for any available volume.
8. Changed the generation of file & directory lists to support links.
9. Resolve relative & absolute links which include '..'.
10. Add UI for chgrp/chown, allowing numeric entries only.
11. Add owner/group to the file display.

The reference for the eXtplorer Volume Browser GUI can be found here.

The eXtplorer licenses and the source to the original un-modified eXtplorer can be found on the Filer appliances in /mnt/monitor/.volume_browser/LICENSES/.

Typical Usage

The following sections describe the configuration of Filer_Linux in several typical use cases:

formatting a volume

Example:

Filer_Linux executes mkfs over the dst volume, specifying a filesystem type of reiserfs.

formatting an ext3-snapshot volume

Example:

Filer_Linux creates a volume group named VGVOL on the dst volume. It then creates a partition named data in the volume group. This partition uses 75% of the space on the dst volume and is formatted with ext3. The remaining partition is for snapshots and is named snap.

filesystem-level volume copy

Example:

Filer_Linux formats the dst volume to ext3 with mkfs. It then mounts the src volume read-only and mounts the dst volume read-write. Finally, Filer_Linux copies the contents of the src volume to the dst volume using cp and unmounts both volumes.

file system check

Example:

Filer_Linux executes fsck on the dst volume.

file system check with repair

Example:

Filer_Linux executes fsck with the repair option on the dst volume.

user-level access to volume

Example:

Filer_Linux mounts the dst volume read-write at /mnt/vol. It then starts the eXtplorer GUI and starts sshd, which gives the user root access to the volume. The GUI is accessible through the default interface and any file transfers to/from the volume is through the external interface.

Notes

• the Linux Filer is based on Ubuntu 7.04
• in non-manual mode, there is no SSH or GUI access

3rd party open source software used inside of the appliance

Filer_Linux uses the following 3rd party open source packages in addition to its base OS install of Ubuntu 7.04.

To see the full list of open source packages used in this appliance, please see its Implementation Design.

Related Documents

• Test Plan
• Implementation Design

-- ApoorvaKulkarni - 26 Jan 2010