Firejail: Firejail does not work with a custom hosts file
When running firejail with a custom hosts file:
$ firejail --noprofile --private --hosts-file=hosts firefox -no-remote
it reports the following errors:
Parent pid 32480, child pid 32481
Error: invalid /etc/hosts file
Error: proc 32480 cannot sync with peer: unexpected EOF
Peer 32481 unexpectedly exited with status 1
My hosts file contains only:
127.0.0.1 sample.localhost
Even with an empty file, it report the same errors.
Firejail Version: 0.9.58
Linux Distribution: NixOS 19.03
rmrgh
All 6 comments
Can't reproduce with firejail 0.9.61 under Fedora 29.
$ firejail --private --noprofile --hosts-file=hfile firefox-wayland -no-remote
… No Error about hosts
$ cat hfile
127.0.0.1 some.localhost
rusty-snake
on 11 Jun 2019
I even just tried firejail --hosts-file=/dev/null and it worked.
chiraag-nataraj
on 11 Jun 2019
There could be two reasons it to fail: if the host file is a symbolic link, or if the user doesn't have read access to the file. Also, try to put a full path for the host file, something like "--host-file=/home/username/hostfile". Works fine on 0.9.58, that code didn't change in ages.
netblue30
on 11 Jun 2019
I've tried with a VoidLinux installation with firejail version 0.9.60 and it worked just fine. I think it's something specific for NixOS since the /etc/hosts present on it is a symbolic link and can't be directly manipulated (readonly). But since i'm providing a custom hosts file it shouldn't present this error. Does firejail check the system /etc/hosts at some moment when running with --hosts?
rmrgh
on 11 Jun 2019
I've tested on my VoidLinux installation by moving the /etc/hosts file to a different location and symblinking it back to /etc/hosts and the same error showed up.
rmrgh
on 11 Jun 2019
I got the same issue on Arch with firejail 0.9.62. The file is no symlink and readable by the user.
$ touch /home/michi/empty
$ chmod 777 /home/michi/empty
$ firejail --noprofile --hosts-file=/home/michi/empty
Parent pid 87979, child pid 87980
Error: invalid /etc/hosts file
Error: proc 87979 cannot sync with peer: unexpected EOF
Peer 87980 unexpectedly exited with status 1
Nudin
on 31 Mar 2020
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Most helpful comment
There could be two reasons it to fail: if the host file is a symbolic link, or if the user doesn't have read access to the file. Also, try to put a full path for the host file, something like "--host-file=/home/username/hostfile". Works fine on 0.9.58, that code didn't change in ages.