Debian

How to disable ipv6 in Debian

Evan Davies

Nov 17, 2012 • 1 min read

Here are simple steps to disable ipv6 in Debian:

Comment out anything related to ipv6 in /etc/hosts
SSH. Ensure AddressFamily inet is set in/etc/ssh/sshd_config. Restart ssh.
BIND. Ensure listen-on-v6 { none; }; in/etc/bind/named.conf.options. Restart bind9.
NTP. Ensure -4 option is set in /etc/default/ntp (e.g. NTPD_OPTS=’-4 -g’). Restart ntp.
APACHE2. Ensure Listen 0.0.0.0:80 in/etc/apache2/ports.conf file. Restart apache2.

RPCBIND (rpc.statd, rpc.mountd). Comment out the appropriate entries in /etc/netconfig:

udp        tpi_clts      v     inet     udp     - -
tcp        tpi_cots_ord  v     inet     tcp     - -
#udp6       tpi_clts      v     inet6    udp    - -
#tcp6       tpi_cots_ord  v     inet6    tcp    - -
rawip      tpi_raw       -     inet      -      - -
local      tpi_cots_ord  -     loopback  -      - -
unix       tpi_cots_ord  -     loopback  -      - -

PostgreSQL 9. Ensure ipv4 in listen_addresses (file/etc/postgresql/9.1/main/postgresql.conf):
```
# - Connection Settings
listen_addresses = '0.0.0.0'
```
Comment out lines related to ipv6 (file/etc/postgresql/9.1/main/pg_hba.conf):
```
# IPv6 local connections:
#host  all     all     ::1/128   md5
```
Restart postgresql.

Disable ipv6 in kernel:

echo net.ipv6.conf.all.disable_ipv6=1 \
> /etc/sysctl.d/disableipv6.conf

Disable ipv6 in kernel modules (file/etc/modprobe.d/aliases.conf):
```
# alias net-pf-10 ipv6
alias net-pf-10 off
alias ipv6 off
```

The next time the system boots it will have ipv6 disabled. Let verify it with:

netstat -tunlp

Here is a sample output:

Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address           Foreign Address   State    PID/Program name
tcp        0      0 192.168.10.2:53         0.0.0.0:*         LISTEN      895/named       
tcp        0      0 127.0.0.1:53            0.0.0.0:*         LISTEN      895/named       
tcp        0      0 0.0.0.0:22              0.0.0.0:*         LISTEN      734/sshd        
tcp        0      0 127.0.0.1:953           0.0.0.0:*         LISTEN      895/named       
udp        0      0 192.168.10.2:53         0.0.0.0:*                     895/named       
udp        0      0 127.0.0.1:53            0.0.0.0:*                     895/named