# Replacing line using lineinfile results in multiple insertions even when line isn't present

**URL:** <https://forum.ansible.com/t/replacing-line-using-lineinfile-results-in-multiple-insertions-even-when-line-isnt-present/13663>\
**Category:** Ansible Project\
**Created:** [October 11, 2013, 2:18pm UTC](https://forum.ansible.com/t/replacing-line-using-lineinfile-results-in-multiple-insertions-even-when-line-isnt-present/13663 "2013-10-11T14:18:00Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Andrew\_Martin](https://avatars.discourse-cdn.com/v4/letter/a/77aa72/32.png) [@Andrew\_Martin](https://forum.ansible.com/u/Andrew_Martin)\
**Post date:** [October 11, 2013, 2:18pm UTC](https://forum.ansible.com/t/replacing-line-using-lineinfile-results-in-multiple-insertions-even-when-line-isnt-present/13663/1 "2013-10-11T14:18:00Z")

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Hello,

I am working on a playbook that would automatically add a bridge network device to /etc/network/interfaces (on Debian-based distributions); this new interface should replace the existing config for the specified ethX port (e.g. eth0).

Before playbook:

# The loopback network interface

auto lo  
iface lo inet loopback

auto eth0

iface eth0 inet dhcp

After playbook:

# The loopback network interface

auto lo  
iface lo inet loopback

# bridge interface for kvm

auto br0  
iface br0 inet dhcp  
bridge\_ports eth0  
bridge\_stp on  
bridge\_fd 0

I have a variable, interface\_num, defined to specify which eth device entry to modify, e.g. this example would replace settings for eth0 with br0:

interface\_comment: ‘# bridge interface for kvm’  
interface\_num: 0

Ideally I’d just match the two eth0 lines above and replace them with the 5 br0 lines using a single task, however added \n to the task appeared to make it no longer match. I did get it working using the following tasks, which first replaces the “auto eth0” line with a comment, then deletes the “iface eth0 inet dhcp” line, and finally uses the inserted comment as an anchor to insert each br0 line:

- name: remove existing ethX in /etc/network/interfaces (part 1)  
tag: networking  
lineinfile: dest=/etc/network/interfaces  
backup=yes  
regexp=“^auto eth${interface\_num}$”  
line=‘${interface\_comment}’  
state=present

- name: remove existing ethX in /etc/network/interfaces (part 2)  
tag: networking  
lineinfile: dest=/etc/network/interfaces  
backup=no  
regexp=‘^iface eth${interface\_num} inet [a-z]+$’  
state=absent

- name: add bridge interface to /etc/network/interfaces  
tag: networking  
lineinfile: dest=/etc/network/interfaces  
backup=no  
regexp=‘${item}’  
line=‘${item}’  
insertafter=‘${interface\_comment}’  
state=present

# insert the new bridge interface; the following lines must be in reverse order

with\_items:

- ’ bridge\_fd 0’
- ’ bridge\_stp on’
- ’ bridge\_ports eth${interface\_num}’
- ‘iface br${interface\_num} inet dhcp’
- ‘auto br${interface\_num}’  
notify: restart networking

This works, however if I run the playbook multiple times on the system, each time after the initial play the “remove existing ethX in /etc/network/interfaces (part 1)” task adds a new comment at the end of the file. Thus, running it 4 times would result in the following file:

# The loopback network interface

auto lo  
iface lo inet loopback

# bridge interface for kvm

auto br0  
iface br0 inet dhcp  
bridge\_ports eth0  
bridge\_stp on  
bridge\_fd 0

# bridge interface for kvm

# bridge interface for kvm

# bridge interface for kvm

Can someone help me determine why this task seems to be matching, even when “auto eth0” does not exist in the file, or do you have a suggestion about a better way to do this? I don’t want to use a template in this case because I don’t know if there will be other interfaces present in the file and prefer to just replace the lines associated with the desired interface.

Thanks,

Andrew Martin

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<div class="post-metadata">

**Author:** ![Andrew\_Martin](https://avatars.discourse-cdn.com/v4/letter/a/77aa72/32.png) [@Andrew\_Martin](https://forum.ansible.com/u/Andrew_Martin)\
**Post date:** [October 21, 2013, 2:25pm UTC](https://forum.ansible.com/t/replacing-line-using-lineinfile-results-in-multiple-insertions-even-when-line-isnt-present/13663/2 "2013-10-21T14:25:05Z")

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Any ideas on why this is occurring?

Thanks!

Andrew

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**Author:** ![PhilEv](https://avatars.discourse-cdn.com/v4/letter/p/ee59a6/32.png) [@PhilEv](https://forum.ansible.com/u/PhilEv)\
**Post date:** [October 22, 2013, 12:17pm UTC](https://forum.ansible.com/t/replacing-line-using-lineinfile-results-in-multiple-insertions-even-when-line-isnt-present/13663/3 "2013-10-22T12:17:11Z")

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Because, related to the first task that’s the way lineinfile works.  
If no match found but state=present the ‘line’ will be added

to avoid this just add

backrefs=yes

to the first task.

HTH

Phil.