[Mellanox] mlnx-fw-manager.service: escape backslashes in ExecCondition to silence systemd parser warning

[yizhenzha]

Why I did it

https://github.com/sonic-net/sonic-buildimage/pull/26549 added an ExecCondition to platform/mellanox/files/mlnx-fw-manager.service:

ExecCondition=/bin/grep -qv '\<SONIC_BOOT_TYPE=fastfast\>' /proc/cmdline

systemd's unit-file parser treats \ as an escape character and does not recognize \< or \>, so on every boot and on every systemctl daemon-reload it logs the following warning, polluting syslog:

systemd[1]: /usr/lib/systemd/system/mlnx-fw-manager.service:25: Ignoring unknown escape sequences: "<SONIC_BOOT_TYPE=fastfast>"

How I did it

• Escaped the backslashes in the ExecCondition so that systemd hands the literal \< / \> word-boundary anchors through to grep:

ExecCondition=/bin/grep -qv '\\<SONIC_BOOT_TYPE=fastfast\\>' /proc/cmdline

• \\ is a documented systemd escape that resolves to a single \, so the argv[] passed to /bin/grep is byte-identical to the previous version. Only the parser warning is removed; runtime behavior is unchanged.

How to verify it

### test before fix applies, warning produced
$ sudo cp /tmp/mlnx-fw-manager.service.old /usr/lib/systemd/system/mlnx-fw-manager.service 
$ sudo systemd-analyze verify /usr/lib/systemd/system/mlnx-fw-manager.service 2>&1 | tee /tmp/sd-old.log 
/usr/lib/systemd/system/mlnx-fw-manager.service:25: Ignoring unknown escape sequences: "<SONIC_BOOT_TYPE=fastfast>" 
$ grep -q 'Ignoring unknown escape' /tmp/sd-old.log && echo 'OLD: WARNING REPRODUCED (expected)' || echo 'OLD: NO WARNING (unexpected)' 
OLD: WARNING REPRODUCED (expected)

### test after fix applied, warning disappear
$ sudo cp /tmp/mlnx-fw-manager.service.new /usr/lib/systemd/system/mlnx-fw-manager.service 
$ sudo systemd-analyze verify /usr/lib/systemd/system/mlnx-fw-manager.service 2>&1 | tee /tmp/sd-new.log 
$ grep -q 'Ignoring unknown escape' /tmp/sd-new.log && echo 'NEW: WARNING (unexpected) - FAIL' || echo 'NEW: NO WARNING (expected) - PASS' 
NEW: NO WARNING (expected) - PASS

Additional checks performed on the same DUT (parity / no behavior change):

• systemctl show mlnx-fw-manager.service -p ExecCondition for OLD and NEW produces a byte-identical argv[] (/bin/grep -qv \<SONIC_BOOT_TYPE=fastfast\> /proc/cmdline); diff of the two outputs is empty.
• systemctl start mlnx-fw-manager.service reports Result=success, ConditionResult=yes, ActiveState=active, SubState=exited with both forms.
• Direct grep -qv regression with the parsed pattern returns 1 / 0 / 0 / 0 for cmdlines SONIC_BOOT_TYPE=fastfast / =fast / =fastfastX / no_match_here under both forms — word-boundary semantics preserved.

Which release branch to backport (provide reason below if selected)

• 201811
• 201911
• 202012
• 202106
• 202111
• 202205
• 202211
• 202305
• 202311
• 202405
• 202411

(Backport is only relevant to branches that already carry PR #26549. Tick the matching release branches if needed.)

Description for the changelog

[mellanox] Fix systemd "Ignoring unknown escape sequences" warning in mlnx-fw-manager.service by doubling the backslashes in the ExecCondition word-boundary anchors.

Summary by CodeRabbit

• Bug Fixes
  • Fixed Mellanox firmware manager service condition so it correctly detects and skips execution when the system boot type indicates a fast boot.
  • Improved reliability of firmware manager startup behavior during special boot scenarios to prevent unintended runs.

[mssonicbld]

/azp run Azure.sonic-buildimage

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