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Write a file on a machine

Have Ysra write a whole text file on a machine after you approve the exact diff, with a backup and a check afterwards.

On this page

Writing a file puts a complete text file on a machine — an nginx site, a systemd unit, an application’s configuration — after you approve the exact content as a diff. Before you start, the machine must be in change mode. For a whole folder, see Deploy a folder.

Steps#

  1. Ask in a thread:

    › put this nginx site on web-01 as /etc/nginx/sites-available/app.conf

  2. Read the card. Its title is Write /path on machine? for a file that exists, or Create /path on machine? for a new one.

    The card shows Example
    What, size and mode Replaces /etc/nginx/sites-available/app.conf on web-01 · 812 bytes · mode 0644
    The diff Old and new line numbers
    On, Why, Expect, Undo As on any change card
    Backup The current file is kept as /path.ysra-bak.

  3. Choose Run it or Skip. Only you can answer; auto mode never does. On a production machine, a file that controls access (SSH files, sudoers) also needs the machine’s name typed.

The file is in place, and the write appears in the machine’s list of what ran as write /path and in the gateway’s log. There is no separate success message.

How the file is written#

Step Detail
In one step The new file replaces the old one whole; a half-written file is never left in place
Backup The old file is kept beside it as <path>.ysra-bak.<time>, for example app.conf.ysra-bak.20261006T115448
Check Ysra compares the file on the machine with what you approved, by checksum
Undo Copy the backup back, or ask Ysra to (it asks first)

Which approval kind it counts as#

For signed approvals:

File Kind
Most files config
SSH files, such as authorized_keys or sshd_config access
sudoers, passwd and similar users

If it doesn’t work#

Case Ysra says
A secret file That’s a secret file (keys, passwords, credentials); I don’t write those on machines.
A symbolic link /path is a link (to …); I write only the file itself, so name that instead.
Not a regular file /path isn’t a regular file, so I didn’t write it.
Content over 256 KB Refused. Split it, or copy the file yourself
A look-only machine web-01 is in observe mode, so I only look there. Switching it to change mode is your call (ysra machines mode web-01 change).
You chose Skip, or didn’t answer You didn’t approve that, so I didn’t write it.
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