looking for jail tutorial
bob at a1poweruser.com
bob at a1poweruser.com
Sun Apr 3 16:50:42 PDT 2005
You should search this lists archives for answers first.
In the list archives I found this.
http://subwiki.honeypot.net/cgi-bin/view/Freebsd/JailAdmin
http://jailnotes.cg.nu/
> Does anyone have any bright ideas for good file system layouts
when
> running multiple jails?
I won't say they are bright, but the ideas reflected in
this layout are working well for me:
/jails/ Home for most jail related material. Note I do not
backup /jails every night as I do other partitions.
(I do backup /data every night and you'll see below
how I make use of that in a jail.)
/jails is its own partition so if it fills, it will
not cause problems for the host system.
/jails/{jail_X}/
The root for one specific jail. Of course if you
have sets of jails, then /jails/jail_A/{cell_1,cell_2}
and /jails/jail_B/{cell_10,cell_11} where cell_#
is actually the root directory works well for
keeping them well organized.
/jails/etc/rc.d/
Startup scripts (e.g. jail_X.sh) for all jails.
If you augment $local_startup in /etc/rc.conf to
include /jails/etc/rc.d then all the jails will be
started automatically.
/jails/bin/
Jail management scripts.
.../bin/JAIL_CTL.sh A generic start, stop, enter, trace,
ps script. Each jail's startup
script sets a bunch of environment
variables and then calls JAIL_CTL.
.../bin/jail_clone duplicates a jail.
.../bin/jail_ps runs ps for all the processes in
a specific jail.
/jails/var/trace/
Home for kdump traces of jail execution.
/jails/template/
A reference jail that I can clone in a few minutes
time. Much easier then running (make world) every
time I need a new jail.
/data/jails/{jail_X}/
If there is a /data/jails/{jail_X} present, then
it is automatically mounted as /jails/{jail_X}/data
when the jail is started. That way the /data
directory in a jail can be treated separately then
from the rest of the jail.
One caveat if you do this. Multiple jails, each
with their own uid space, will rapidly overlap in
the host's uid space. To avoid this, my jail creation
script hashes the jail's IP address to create a
(relatively) unique starting point for that jail's
uids. That starting uid is placed in the jail's
/etc/adduser.conf as $uid_start. This minimizes the
chances that uids will collide.
/data/jails/{jail_X}/home/
Symlink to /data/home (in the jail of course). If
/data/jails/{jail_X} is mounted on the jail's /data,
then the home partition in the jail is actually
coming from /data of the host and therefore will
be backed up on a regular basis.
/data/jails/{jail_X}/proc/
If it is present, then /proc is mounted on this
directory when a jail is started and unmounted when
it is stopped.
> How do I stop /var/log in one the jails from filling up the whole
drive
> and affecting the rest without giving each jail it's own
partition?
>
> Is it possible to some how set a quota on how large a particular
> directory can get?
About all I can think of is to make a directory, and all its
subordinate directories, owned by a specific user. You can
then have per user quotas.
For the specific example of /var/log, you'd have to set the
user to be root_X. If you then set the user-ID-on-execution
bit (see chmod(1) or chmod(2)) for /var/log so all new files
and directories created under it would also be owned by root_X.
I suspect you'd have to pre-populate your /var/log directory
and chown everything to root_X. If you then change everything
there to have world write permissions then root in the jail
can update the files. Having world write access is a bad
idea, but it's your trade-off to consider.
managing passwd in a jailed env.
Well i have the answer. just ran across the pw
command, and looked it up. guess what i found.
pw -V etcdir
daoh!
pw -V /usr/jail1/etc adduser bubba
daoh, daoh!!
pw -V /usr/jail1/etc usermod bubba -h 0
New password for user bubba:
dd if=/dev/daoh of=/dev/stdout bs=1048576 count=1
so to some up, pw does everything i need to manage
users in a jail, from outside of the jail.
i knew there was something out there to do this with.
-----Original Message-----
From: owner-freebsd-questions at freebsd.org
[mailto:owner-freebsd-questions at freebsd.org]On Behalf Of Bill Ding
Sent: Sunday, April 03, 2005 7:23 PM
To: freebsd-questions at freebsd.org
Subject: looking for jail tutorial
Hello,
Running 5.3-p6 on a box with two NICs.
I'm new to the list and FreeBSD in general. I'm trying
to find more documentation on jail(8) than is offered
in the man page. (I checked the Handbook but couldn't
find anything about jails. Did I miss it?) For
instance, the man page says:
NOTE: It is important that only appropriate device
nodes in devfs be exposed to a jail; access to disk
devices in the jail may permit processes in the jail
to
bypass the jail sandboxing by modifying files outside
of the jail.
How do I know what the "appropriate device nodes" are
for a given jail? I want to run four jails: two
webservers, DNS, mail. After testing, the DNS and
email jails will be shutdown and the services moved to
separate machines.
Also, do I configure identical Hosts files on each?
Should the jails be on different subnets for added
security or can they all be on the same subnet as the
host machine?
Any help you can give would be appreciated!
Thanx,
Bill
The word 'politics' describes the situation so well:
'poli' meaning 'many' and 'tics' meaning 'bloodsucking
creatures'.
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