Tag Archives: Jailer

Antranig Vartanian ✔

March 29, 2023

After weeks of thinking, I decided that I need to fork Jailer. Yes, I want to fork my own code. There are two reasons to do this.

  1. Keep the promise of Jailer being “very compatible with FreeBSD”
  2. Have a new version that pushes these limits of compatibility.

The fork is going to be named bant, which is Armenian for jail. I think we’re all tired of Greek names at this point 🙂

I’ll share the details of bant as soon as I have a prototype, which means at least couple of weeks.

Meanwhile, Jailer will be the very-compatible-with-FreeBSD version, that doesn’t brake things and allows new users to use Jails with ease.

Fingers crossed…

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Antranig Vartanian ✔

March 29, 2023

Code cleanup is hard. I’ve been trying to make Jailer’s code simpler, more modular for hours now, and the more I try to simplify it, the harder it is.

My biggest issue right now is this massive complex code that does image management. The end goal is to make it so simple, that anyone with basic knowledge if shell can understand it.

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Design Guidelines vs Pushing The Limits

One of the design guidelines of Jailer is don’t break FreeBSD. As in if someone installed and used Jailer, and then deleted the Jailer binary and libraries, their Jails would still run without any issues. We do this with minimal intervention, for example, jailer init patches FreeBSD’s /etc/rc.d/jail, but in a way that you wouldn’t feel the difference much. We don’t create new rc.conf variables, we just change couple of loops. In a way, you can keep these changes even if you delete Jailer so your system would be much improved. Obviously, we do sent these patches to FreeBSD src.

But I’m in front of an issue right now. On one side, I want to keep these guidelines, on the other, pushing the limit will allow me to improve Jailer way more than I expected.

These are the things that I think about before sleep, or during the shower. I gave a promise, that I will not break the Jail ecosystem. But what if, just what if, the ecosystem was broken in the first place?

Some of you might know, that we’ve been working on integrating libucl with Jail. The experiments have been going well, in such that I feel I want to integrate these experiments with Jailer already, even before they get into FreeBSD (and they might even not get in at all).

My dream of Jailer and its ecosystem is complex. I feel that these integration would do good on the long-term, but I want to keep the short term alive as well.

One idea is to fork Jailer, keep two versions of it. One version that’s FreeBSD compliant, and another one that is pushing the limits.

This is going to be an interesting week…

That’s all folks…

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Call For Testing: Jailer v0.1.1

Well, it’s finally here! After a week of sleepless work, I cleaned up the Jailer codebase and added many features (and removed some as well!) that I wanted since last year 🙂

If you are reading this, please consider testing Jailer on FreeBSD. The codebase is at illuria/jailer.

The README.md should have all the info that you need to run Jailer.

If find any issues, please report to illuria/jailer/issues or you can email me personally at antranigv [at] freebsd [dot] am

Here’s the roadmap for what’s coming next

  1. Complete NetGraph support using jng.
  2. Jailerfile, which will be something similar to Dockerfile, allowing developers to create consistent images.
  3. jailerd and jailerctl, for remote jailer automation. This will be an open-source port of what illuria has already developed.
  4. Distributed Jailer, where jailerctl list will show not just what’s on a remote machine, but on a remote datacenter, inspired by Triton. Again, we have this at illuria, but we need to create an open-source port.

This release is dedicated to

Thank you for reading 🙂

That’s all folks…

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Antranig Vartanian ✔

March 3, 2023

I’ve been working very intensively with Jailer the last couple of days.

The first thing I added, which I personally needed it is a dry run, where Jailer says what it would do. Here’s an example.

Screenshot 2023 03 02 at 8 48 08 PM

by adding -D Jailer would display what it would do, including post the jail.conf file, ZFS commands and any network setup commands.

A while back kfv has made a jailer init

subcommand that initializes the system. Things like rc.conf variables, ZFS datasets and applying our own patches. I just added some coloring and confirmation to that!

Screenshot 2023 03 03 at 3 27 35 PM

I think I will be making an official Jailer v0.1.0 release in the coming days!

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VoidLinux in FreeBSD Jail; with init

Two important things happened this week for me.

First, Faraz asked me if I can rename my Jail manager to something other than Jailio because he got that domain for his Jailer manager already. So I named it

Second, I was able to run a complete Linux system using Jailer. While the repo for Jailer is not released yet (we are auditing for possible security issues), I would like to share how I was able to run VoidLinux in a Jail.

Since Jailer is not announced yet, I will give the examples using jail.conf, as most people either are or should be familiar with its concepts.

I went with VoidLinux because I am able to run the init process without its need to be running as PID1.

Let’s start, shall we?

First, ZFS dataset for our jail!

zfs create zroot/jails/voidlinux

Next we need to fetch the base system of VoidLinux. Luckily they do provide it on their website.

fetch https://alpha.de.repo.voidlinux.org/live/current/void-x86_64-ROOTFS-20210218.tar.xz

Now we can extract this into our dataset

tar xf void-x86_64-ROOTFS-20210218.tar.xz -C /usr/local/jails/voidlinux/

You might get an error that ./usr/bin/iputils-ping: Cannot restore extended attributes: security.capability, which is fine, I think?

If you are on FreeBSD 12.2-RELEASE or later, now you need to enable the Linuxulator.

service linux enable; service linux start

Now you can at least chroot into the system.

chroot /usr/local/jails/voidlinux/ /bin/bash

If everything is fine until now, perfect.

Now we need to add a root user into the system.

root@host:~ # cd /usr/local/jails/voidlinux/etc/
root@host:/usr/local/jails/voidlinux/etc # echo "root::0:0::0:0:Charlie &:/root:/bin/bash" > master.passwd
root@host:/usr/local/jails/voidlinux/etc # pwd_mkdb -d ./ -p master.passwd
pwd_mkdb: warning, unknown root shell

Execute the rest of the commands in Void.

root@host:~ # chroot /usr/local/jails/voidlinux/ /bin/bash
bash-5.1# cd /etc/
bash-5.1# pwconv 
bash-5.1# grpconv 
bash-5.1# passwd 
New password: 
Retype new password: 
passwd: password updated successfully
bash-5.1# exit

If all went fine, then the system is ready to be run as a Jail!

First we need to make an fstab for the system.

Create a file at /usr/local/jails/voidlinux/etc/fstab.pre and insert the following inside

devfs       /usr/local/jails/voidlinux/dev      devfs           rw                      0   0
tmpfs       /usr/local/jails/voidlinux/dev/shm  tmpfs           rw,size=1g,mode=1777    0   0
fdescfs     /usr/local/jails/voidlinux/dev/fd   fdescfs         rw,linrdlnk             0   0
linprocfs   /usr/local/jails/voidlinux/proc     linprocfs       rw                      0   0
linsysfs    /usr/local/jails/voidlinux/sys      linsysfs        rw                      0   0
/tmp        /usr/local/jails/voidlinux/tmp      nullfs          rw                      0   0

Next, let’s create a loopback interface for networking. Oh yes, VNET is not supported yet, but I’m working on a patch 🙂

ifconfig lo1 create
ifconfig lo1 inet up # sorry, was unavailable :P

Okay, time to create our Jail conf!


voidlinux {
    $id     = "1";
    $ipaddr = "";
    $mask   = "";
    $domain = "srv0.bsd.am";
    devfs_ruleset  = 4;
    mount.fstab = "${path}/etc/fstab.pre";

    exec.start     = "/bin/sh /etc/runit/2 &";
    exec.stop      = "/bin/sh /etc/runit/3";

    ip4.addr      = "${ipaddr}";
    interface     = "lo1";
    host.hostname = "${name}.${domain}";
    path = "/usr/local/jails/voidlinux";
    exec.consolelog = "/var/log/jail-${name}.log";

Let’s check?

# jls
   JID  IP Address      Hostname                      Path
     1    voidlinux.srv0.bsd.am         /usr/local/jails/voidlinux

And the process tree?

# ps auxd -J voidlinux
root 35182  0.0  0.1 2320 1428  -  SsJ  21:09   0:00.12 runsvdir -P /run/runit/runsvdir/current log: ot set SO_PASSCRED: Protocol not available\ncould not set SO_PASSCRED: Protocol
root 35190  0.0  0.1 2168 1376  -  SsJ  21:09   0:00.02 - runsv agetty-tty6
root 35397  0.0  0.1 2412 1704  -  SsJ  21:10   0:00.00 `-- agetty tty6 38400 linux
root 35191  0.0  0.1 2168 1376  -  SsJ  21:09   0:00.02 - runsv agetty-tty1
root 35396  0.0  0.1 2412 1704  -  SsJ  21:10   0:00.00 `-- agetty --noclear tty1 38400 linux
root 35192  0.0  0.1 2168 1376  -  SsJ  21:09   0:00.02 - runsv agetty-tty5
root 35398  0.0  0.1 2412 1704  -  SsJ  21:10   0:00.01 `-- agetty tty5 38400 linux
root 35193  0.0  0.1 2168 1376  -  SsJ  21:09   0:00.02 - runsv agetty-tty2
root 35393  0.0  0.1 2412 1704  -  SsJ  21:10   0:00.00 `-- agetty tty2 38400 linux
root 35194  0.0  0.1 2168 1396  -  RsJ  21:09   0:00.12 - runsv udevd
root 35195  0.0  0.1 2168 1376  -  SsJ  21:09   0:00.02 - runsv agetty-tty3
root 35394  0.0  0.1 2412 1704  -  SsJ  21:10   0:00.00 `-- agetty tty3 38400 linux
root 35196  0.0  0.1 2168 1376  -  SsJ  21:09   0:00.02 - runsv agetty-tty4
root 35390  0.0  0.1 2412 1704  -  SsJ  21:10   0:00.00 `-- agetty tty4 38400 linux

You may jexec now 🙂

# jexec voidlinux /bin/bash
bash-5.1# uname -a
Linux voidlinux.srv0.bsd.am 3.2.0 FreeBSD 12.2-RELEASE-p6 GENERIC x86_64 GNU/Linux

Let’s check networking?

bash-5.1# ping -c 1
ping: WARNING: setsockopt(ICMP_FILTER): Protocol not available
PING ( 56(84) bytes of data.
64 bytes from icmp_seq=1 ttl=64 time=0.069 ms

--- ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.069/0.069/0.069/0.000 ms

There you go! Well, things that are related to netlink might not work, but other than that it’s okay.

I did have some problems while installing packages, something about too many levels of symbolic links. Here’s the exact output when I was trying to install the curl package

[*] Unpacking packages
libev-4.33_1: unpacking ...
ERROR: libev-4.33_1: [unpack] failed to extract file `./usr/lib/libev.so.4': Too many levels of symbolic links
ERROR: libev-4.33_1: [unpack] failed to extract files: Too many levels of symbolic links
ERROR: libev-4.33_1: [unpack] failed to unpack files from archive: Too many levels of symbolic links
Transaction failed! see above for errors.

Now, I did not find the time to fix this yet, but if you have any idea, please let me know or comment below 🙂

So, what do we have here? A Linux Jail, running VoidLinux, with init, so you can also run services, and basic networking for it.

That’s all folks…

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Two Colons Equals Modules

Days ago I tweeted a shell function which is part of jailio’s code base. Jailio is a project I’ve been working on for the last 6 months. As the name implies, it’s a container management software for FreeBSD Jails.

It has two unique things compared to other Jail management software. First of all, it has no dependencies, it’s written purely in Shell. You can say the same about BastilleBSD, however, Jailio’s second unique thing is that it uses base tools only and requires the base system only. For example, you need to have bastille_enable in BastilleBSD, it also uses its own config files, etc. In Jailio, you need to have jail_enable, because technically Jailio automates jail.conf files. It also uses my patch to automate the jail.confs in /etc/jail.conf.d.

Anyway, back to our topic about Colons and Modules.

I like modules, I got introduced to them when I started programming in school. In Syria, we learn programming at 7th grade but in our school we started a year early, so 6th grade. We always start with block diagrams and then Turbo Pascal!

Yes, 16-bit Turbo Pascal was my first programming language and it had the concept of modules which we called Units.

And then you have languages like C or Shell which don’t have modules. If you use modules you KNOW that it’s hard not to use modules after that.

While reading the source code of vm-bhyve I learned that you can use two colons (::) as part of the function name, which can give you an amazing new superpower to take over the world write cleaner code.

For me this was a life-changer. I write a LOT of Shell code. I ship them to production too. No, you don’t need to write everything in a fancy new language and run it on kubernetes, you can always use simple languages like Shell and run them in a FreeBSD Jail. Or in my case, write in Shell to automate FreeBSD Jails.

Here’s an example code with “modules” in Shell. Note, this works in FreeBSD’s shell, I have not tested other Shells yet.



. ./mod1.sh




  printf "Here I am, rock you like a hurricane\n"
antranigv@pingvinashen:~ % ./main.sh 
Here I am, Rock you like a hurricane

As you can see it all relies on the concept that the function name itself has two colons in its name.

Here’s the code from jailio that I tweeted.

  expr $(
    ( grep -s '$id' /etc/jail.conf.d/* || echo '$id = "0";' ) |
    awk -F '[="]' '{print $3}' |
    sort -h |
    tail -1
  ) + 1

After tweeting the code above Annatar replied that this should NOT work elsewhere and that’s how I got introduced to The Heirloom Project which provides traditional implementations of the original Unix tools from the original Unix source code.

Hopefully, I will see more people using “modules” in Shell scripts. Hopefully this trick works in other Shell implementations like Bash and zsh.

That’s all folks.

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