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Attila Csipak
Asked: 2021-12-10 03:24:19 +0800 CST

systemd RequiresMountsFor multiline syntax

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I know that this is a valid systemd unit configuration file syntax:

[Unit]
RequiresMountsFor=/mnt/foo /mnt/bar
...

Recently, I've seen a multiline variant of the above:

[Unit]
RequiresMountsFor=/mnt/foo
RequiresMountsFor=/mnt/bar
...

Are these two syntaxes semantically equivalent?

I checked the RequiresMountsFor option in the systemd.unit manpage, which explicitly states: "Takes a space-separated list of absolute paths." Also there's a hint on similarities with Requires and After options. The Requires option's documentation explicitly states that the single-line and multi-line syntaxes are equivalent (for the Requires option): "This option may be specified more than once or multiple space-separated units may be specified in one option in which case requirement dependencies for all listed names will be created." So I'd guess that the same applies to RequiresMountsFor.

systemd

1 Answers

  1. Best Answer

    Looks like it’s equivalent indeed:

    # tee /run/systemd/system/serverfault-1085820.service >/dev/null << 'EOF'
[Unit]
RequiresMountsFor=/mnt/foo
RequiresMountsFor=/mnt/bar
[Service]
ExecStart=echo hi
EOF
# systemctl daemon-reload
# SYSTEMD_PAGER=cat systemctl show -p RequiresMountsFor serverfault-1085820.service 
RequiresMountsFor=/mnt/bar /mnt/foo

    This should probably be documented better in the manpage; it’s not true for all directives, as systemd.syntax(7) points out:

    Various settings are allowed to be specified more than once, in which case the interpretation depends on the setting. Often, multiple settings form a list, and setting to an empty value "resets", which means that previous assignments are ignored. When this is allowed, it is mentioned in the description of the setting.

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