NAME

appjail-fstab — Static information about the file systems of a jail

SYNOPSIS

DESCRIPTION

The appjail fstab utility adds, removes, mounts, and lists fstab(5) entries. This is all done from the command-line rather than from an fstab(5) file, such an interface is advantageous for automation. appjail-makejail's MOUNT instruction uses this command, for example.

Other advantages are that appjail fstab can make changes to device or mountpoint or treat them with special meaning; the pseudo-filesystems described in PSEUDO-FILESYSTEMS are an example. An example of special treatment is that this command allows you to use spaces in device and mountpoint, which in most cases is not necessary.

This command relies on appjail-start(1) and the template that the jail uses. appjail-start(1) is in charge of calling appjail fstab compile to get an fstab(5) file and set mount.fstab to point to that file, but this is not accomplished when the template has mount.fstab set. This design allows the user to use whatever they prefer.

Use all to run a command on all jails or jail to run a command on a single jail. If the -e parameter of all is specified, this command exits when an error is detected.

When no command is specified, the default is list, but of course you must use it explicitly if you want to use any of its arguments.

The options are as follows:

compile

Create an internal fstab(5) file with the entries that are enabled.

Depending on type, this subcommand performs some other tasks while compiling fstab(5) entries, but when the file system has no special meaning, it creates a directory when mountpoint does not exist.

get [-eHIpt] -n nro [keyword ...]

Get information about an entry, that is, the keyword that represent the information to be obtained. Multiple keywords can be specified, which are displayed as a table-like interface in the order in which they are specified. If no keyword is specified, the defaults are nro, enabled, name, device, mountpoint, type, options, dump and pass.

See KEYWORDS for a list of available keywords.

-e

Not required when using -p. The \t character is used to delimit columns, so as not to show strange values, this option shows <TAB> instead of \t in the case that a value contains the latter.

-H

Shows the name of the columns.

-I

Include empty values. By default, a minus sign is displayed when a value is empty.

-p

Columnate the list.

-t

Tabulate columns and values.

list [-eHIpt] [-n nro] [keyword ...]

Similar to get but shows each keyword for each entry in a nice table.

-e, -H, -I, -p, -t

All of these options perform the opposite task of the options described in get.

-n nro

Only show information for nro.

mounted

Shows the mounted file systems, except those that are ZFS.

It use a right arrow to indicate that device was mounted on mountpoint and a left arrow to indicate that mountpoint was mounted on device.

mount [args ...]

Wrapper for mount(8) with the -F parameter set to the internal fstab(5) file. mount(8) is run from the host but the working directory is set to the jail directory.

remove [all|nro nro]

Remove a given entry.

all

Remove all entries.

nro nro

Remove the entry specified by nro.

set -d device -m mountpoint [-E|-e] [-p] [-D dump] [-N name] [-n [auto|nro]] [-o options] [-P pass] [-t type]

Configure a new or existing entry.

-d device

Special device or remote file system to be mounted.

If you are configuring an entry that already has this value, it becomes optional, so you can ignore it if you wish.

Depending on type, this may have a special meaning. See PSEUDO-FILESYSTEMS.

-m mountpoint

Mount point for the file system.

If you are configuring an entry that already has this value, it becomes optional, so you can ignore it if you wish.

Depending on type, this may have a special meaning. See PSEUDO-FILESYSTEMS.

[-E|-e]

Enable (-E) or disable (-e) this entry.

-p

Deprecated. Currently this is a no-op parameter.

-D dump

Used for these file systems by the dump(8) command to determine which file systems need to be dumped. The default is 0.

-N name

Entry description.

-n [auto|nro]

Identifier. An identifier is composed of a positive number. Use auto (default) to get the lowest identifier value.

-o options

Mount options associated with the file system. The default is rw.

-P pass

Used by the fsck(8) and quotacheck(8) programs to determine the order in which file system and quota checks are done at reboot time. The default is 0.

-t type

Type of file system. The default is nullfs.

See PSEUDO-FILESYSTEMS.

umount args ...

Wrapper for umount(8) with the -F parameter set to the internal fstab(5) file. umount(8) is run from the host but the working directory is set to the jail directory.

KEYWORDS

enabled

Shows 1 if the entry is enabled, 0 if it is not.

nro

Identifier.

name

Entry description.

device

Special device or remote file system to be mounted.

mountpoint

Mount point for the file system.

type

Type of file system.

options

Mount options associated with the file system.

dump

Used for these file systems by the dump(8) command to determine which file systems need to be dumped.

pass

Used by the fsck(8) and quotacheck(8) programs to determine the order in which file system and quota checks are done at reboot time.

PSEUDO-FILESYSTEMS

A pseudo-filesystem, at least in AppJail, is a file system that does not exist on your system, but performs a specific task. Except for nullfs(5), the following are considered pseudo-filesystems.

nullfs

As mentioned, nullfs(5) is not a pseudo-filesystem since it exists on your system and can be used via mount_nullfs(5), but it treats device and mountpoint with special meaning.

If device is a file, an empty file is created and mountpoint is used as the pathname. The same thing happens when device is a directory, but a directory is created instead of a file. An error occurs when mountpoint exists but is not the same file type as device.

An error occurs when device does not exist.

<pseudofs>

<pseudofs> is a pseudo-filesystem that moves files from mountpoint to device before mounting device on mountpoint using nullfs(5). The goal is to create the illusion that two directories overlap like unionfs(5) does, but we are actually manipulating a single file or directory.

The reason to use this pseudo-filesystem is when we need to mount a file or directory from the host to the jail, but the file or directory inside the jail has content, so if we simply use nullfs, the lower layer will “disappear” when the upper layer is mounted.

Before this pseudo-filesystem does its job, it also does what nullfs describes.

<volumefs>

<volumefs> is a pseudo-filesystem that does what <pseudofs> or nullfs do, plus it can change the owner, group and file mode of a file or directory. The user creates a volume using appjail-volume(1), sets the file system type to <volumefs> and sets the mountpoint to the volume name; appjail fstab will use the volume name to get the necessary properties such as uid, gid, file mode and mountpoint.

The purpose of this pseudo-filesystem is to take away the responsibility of teaching the user what properties a mountpoint should have, since applications inside a jail may have different requirements, it is not feasible for the user to do this job. The developer of a Makejail, commonly through an image, specifies which volumes the Makejail should use and the user only needs to know which volume names they should use.

nullfs:reverse, <pseudofs>:reverse

Using the :reverse prefix for nullfs and <pseudofs> file systems, device is mountpoint and mountpoint is device.

EXIT STATUS

The appjail fstab utility exits 0 on success, and >0 if an error occurs.

SEE ALSO

appjail-volume(1) sysexits(3) fstab(5) nullfs(5) unionfs(5) mount(8) mount_nullfs(8) mount_unionfs(8)

AUTHORS

Jesús Daniel Colmenares Oviedo <DtxdF@disroot.org>