Bug#862013: initramfs-tools-core: /run tmpfs size hardcoded at 10% RAM, but 16.0 MiB free required in /run/systemd

[Benjamin Drung]

Hi,

Using 10% of RAM for /run is a good default, but not suitable for all
systems. 10% might be too small for system with less memory (e.g.
virtual machine with 160 MiB RAM) or too big (VM host with 256/512 GiB
RAM). A too small /run partition leads to not enough space on it. If
the
/run partition is huge, systemd's journald will consume lot of memory,
because it defaults to using at most 15% of the respective file system
of /run/log/journal.

Adjusting the size of /run via an entry in /etc/fstab is not sufficient
since journald calculates it limits before systemd remounts /run with
the small size. Therefore journald could occupy the full /run partition
with its logs.

Allow specifying the size of /run by adding a RUNSIZE configuration
variable and a ramsize= boot argument. Mounting /run must be done after
reading the configuration.

A tested patch is attached and I created a merge proposal:
https://salsa.debian.org/kernel-team/initramfs-tools/merge_requests/2

-- 
Benjamin Drung
System Developer
Debian & Ubuntu Developer

ProfitBricks GmbH
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Email: benjamin.dr...@profitbricks.com
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Geschäftsführer: Achim Weiss, Matthias Steinberg, Christoph SteffensFrom 6569b72cad0145843b55022fa6bc9e00a75a6d79 Mon Sep 17 00:00:00 2001
From: Benjamin Drung 
Date: Tue, 15 May 2018 12:12:56 +0200
Subject: [PATCH] Make size of /run configurable

Using 10% of RAM for /run is a good default, but not suitable for all
systems. 10% might be too small for system with less memory (e.g.
virtual machine with 160 MiB RAM) or too big (VM host with 256/512 GiB
RAM). A too small /run partition leads to not enough space on it. If the
/run partition is huge, systemd's journald will consume lot of memory,
because it defaults to using at most 15% of the respective file system
of /run/log/journal.

Adjusting the size of /run via an entry in /etc/fstab is not sufficient
since journald calculates it limits before systemd remounts /run with
the small size. Therefore journald could occupy the full /run partition
with its logs.

Allow specifying the size of /run by adding a RUNSIZE configuration
variable and a ramsize= boot argument. Mounting /run must be done after
reading the configuration.

Closes: #862013
Signed-off-by: Benjamin Drung 
---
 conf/initramfs.conf | 11 +++
 init| 19 ++-
 initramfs-tools.8   |  7 +++
 3 files changed, 32 insertions(+), 5 deletions(-)

diff --git a/conf/initramfs.conf b/conf/initramfs.conf
index f0f5071..da862bc 100644
--- a/conf/initramfs.conf
+++ b/conf/initramfs.conf
@@ -62,3 +62,14 @@ DEVICE=
 
 NFSROOT=auto
 
+#
+# RUNSIZE: ...
+#
+# The size of the /run mount point in bytes, and rounded up to entire pages.
+# This option accepts a suffix % to limit the instance to that percentage of
+# your physical RAM or a suffix k, m or g for Ki, Mi, Gi (binary kilo (kibi),
+# binary mega (mebi) and binary giga (gibi)).
+# Overridden by optional ramsize= bootarg
+#
+
+RUNSIZE=10%
diff --git a/init b/init
index 8a40b42..aa2fae6 100755
--- a/init
+++ b/init
@@ -33,8 +33,6 @@ export quiet
 mount -t devtmpfs -o nosuid,mode=0755 udev /dev
 mkdir /dev/pts
 mount -t devpts -o noexec,nosuid,gid=5,mode=0620 devpts /dev/pts || true
-mount -t tmpfs -o "noexec,nosuid,size=10%,mode=0755" tmpfs /run
-mkdir -m 0755 /run/initramfs
 
 # Export the dpkg architecture
 export DPKG_ARCH=
@@ -101,6 +99,9 @@ for x in $(cat /proc/cmdline); do
 			;;
 		esac
 		;;
+	runsize=*)
+		RUNSIZE="${x#runsize=}"
+		;;
 	nfsroot=*)
 		NFSROOT="${x#nfsroot=}"
 		;;
@@ -147,9 +148,9 @@ for x in $(cat /proc/cmdline); do
 		debug=y
 		quiet=n
 		if [ -n "${netconsole}" ]; then
-			exec >/dev/kmsg 2>&1
+			log_output=/dev/kmsg
 		else
-			exec >/run/initramfs/initramfs.debug 2>&1
+			log_output=/run/initramfs/initramfs.debug
 		fi
 		set -x
 		;;
@@ -169,7 +170,7 @@ for x in $(cat /proc/cmdline); do
 		;;
 	netconsole=*)
 		netconsole=${x#netconsole=}
-		[ "x$debug" = "xy" ] && exec >/dev/kmsg 2>&1
+		[ "x$debug" = "xy" ] && log_output=/dev/kmsg
 		;;
 	BOOTIF=*)
 		BOOTIF=${x#BOOTIF=}
@@ -201,6 +202,14 @@ else
 	resume=${RESUME:-}
 fi
 
+mount -t tmpfs -o "noexec,nosuid,size=${RUNSIZE:-10%},mode=0755" tmpfs /run
+mkdir -m 0755 /run/initramfs
+
+if [ -n "$log_output" ]; then
+	exec >$log_output 2>&1
+	unset log_output
+fi
+
 maybe_break top
 
 # Don't do log messages here to avoid confusing graphical boots
diff --git a/initramfs-tools.8 b/initramfs-tools.8
index 0eee050..61a2fcb 100644
--- a/initramfs-tools.8
+++ b/initramfs-tools.8
@@ -88,6 +88,13 @@ mounts the rootfs read-only.
 \fB\fI rw
 mounts the rootfs read-write.
 
+.TP
+\fB\fI ramsize
+The size of the /run mount point in bytes, and rounded up to entire pages.
+This option accepts a suffix % to limit the instance to that percentage of
+your 

Bug#862013: initramfs-tools-core: /run tmpfs size hardcoded at 10% RAM, but 16.0 MiB free required in /run/systemd

[José M Cerqueira Esteves]

Thanks for the suggestions!

On the subject of RAM requirements, for i386 systems (the case in my
original message) a minimum of 128 MB is still mentioned in  
https://www.debian.org/releases/stable/i386/ch03s04.html.en
Thus it might make sense to automatically cater for such low-mem i386
systems, or at least mention those fstab adjustments in the
installation instructions.

Best regards
J Esteves

Bug#862013: initramfs-tools-core: /run tmpfs size hardcoded at 10% RAM, but 16.0 MiB free required in /run/systemd

[Russell Coker]

On Tuesday, 27 June 2017 4:19:56 AM AEST Michael Biebl wrote:
> > Now what can we do about /dev and /sys/fs/cgroup neither of which needs to
> > be  24G in size on a system with 48G of RAM?  Should I open a new bug
> > report about this?
> 
> What exactly would that solve?
> Neither of those are writable by the user.

In the past I've dealt with buggy scripts running as root, either writing to 
the wrong name of a device or writing to a device that wasn't there.

https://www-uxsup.csx.cam.ac.uk/misc/horror.txt

See Mike Stefanik's entry in the above file for an example.

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My Main Blog http://etbe.coker.com.au/
My Documents Bloghttp://doc.coker.com.au/

Bug#862013: initramfs-tools-core: /run tmpfs size hardcoded at 10% RAM, but 16.0 MiB free required in /run/systemd

[Michael Biebl]

Am 27.06.2017 um 04:03 schrieb Russell Coker:

> Now what can we do about /dev and /sys/fs/cgroup neither of which needs to be 
> 24G in size on a system with 48G of RAM?  Should I open a new bug report 
> about 
> this?

What exactly would that solve?
Neither of those are writable by the user.

Michael
-- 
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universe are pointed away from Earth?



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Bug#862013: initramfs-tools-core: /run tmpfs size hardcoded at 10% RAM, but 16.0 MiB free required in /run/systemd

[Russell Coker]

For /run specifying the number of inodes is also a good idea.  For a system 
with 160M of RAM it will default to 20480 inodes which may be more than you 
want on a system with less than the recommended amount of RAM.

tmpfs /run tmpfs nosuid,noexec,size=20M,nr_inodes=4096 0  0

The above might be more suitable for the use of J M Cerqueira Esteves.

Thanks Michael for suggesting the use of /etc/fstab, I've tested it and it 
solves the issue of /run.

Now what can we do about /dev and /sys/fs/cgroup neither of which needs to be 
24G in size on a system with 48G of RAM?  Should I open a new bug report about 
this?

-- 
My Main Blog http://etbe.coker.com.au/
My Documents Bloghttp://doc.coker.com.au/

Bug#862013: initramfs-tools-core: /run tmpfs size hardcoded at 10% RAM, but 16.0 MiB free required in /run/systemd

[Michael Biebl]

Am 27.06.2017 um 02:08 schrieb Michael Biebl:
> You can add a entry to /etc/fstab which specifies the desired amount of
> RAM for /run.
> systemd will remount /run with the size you set very early during boot.
> I don't think a separate config option is necessary.

Something like this in /etc/fstab should do the trick

tmpfs /run tmpfs nosuid,noexec,size=20M 0  0

Michael
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Bug#862013: initramfs-tools-core: /run tmpfs size hardcoded at 10% RAM, but 16.0 MiB free required in /run/systemd

[Michael Biebl]

On Sun, 07 May 2017 13:38:11 +0100 J M Cerqueira Esteves
 wrote:
> Package: initramfs-tools-core
> Version: 0.130
> Severity: important
> 
> In a virtual machine with 160 MiB RAM, running a freshly installed Debian 
> stretch system (i686),

Since wheezy, the minimum requiremensts are 256M of RAM:
https://www.debian.org/releases/wheezy/amd64/ch03s04.html.en

> got messages like this logged from (at least) sh and ifup:
> 
>"Failed to reload daemon: Refusing to reload, not enough space available 
> on /run/systemd.
> Currently, 15.6M are free, but a safety buffer of 16.0M is enforced."
> 
> I noticed that /usr/share/initramfs-tools/init  mounts /run specifying 
> "size=10%".
> 
> To prevent this issue in machines low on RAM, it would be nice for the /run 
> tmpfs size
> to be automatically set taking into account systemd's minimum requirement.  
> Or, at least,
> to have this size as a nicely (/etc/...) configurable parameter with some 
> warning on README.

You can add a entry to /etc/fstab which specifies the desired amount of
RAM for /run.
systemd will remount /run with the size you set very early during boot.
I don't think a separate config option is necessary.

Michael
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Bug#862013: initramfs-tools-core: /run tmpfs size hardcoded at 10% RAM, but 16.0 MiB free required in /run/systemd

[J M Cerqueira Esteves]

Package: initramfs-tools-core
Version: 0.130
Severity: important

In a virtual machine with 160 MiB RAM, running a freshly installed Debian 
stretch system (i686),
got messages like this logged from (at least) sh and ifup:

   "Failed to reload daemon: Refusing to reload, not enough space available on 
/run/systemd.
Currently, 15.6M are free, but a safety buffer of 16.0M is enforced."

I noticed that /usr/share/initramfs-tools/init  mounts /run specifying 
"size=10%".

To prevent this issue in machines low on RAM, it would be nice for the /run 
tmpfs size
to be automatically set taking into account systemd's minimum requirement.  Or, 
at least,
to have this size as a nicely (/etc/...) configurable parameter with some 
warning on README.

-- System Information:
Debian Release: 9.0
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: i386
 (i686)

Kernel: Linux 4.9.0-2-686-pae (SMP w/1 CPU core)
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages initramfs-tools-core depends on:
ii  cpio 2.11+dfsg-6
ii  klibc-utils  2.0.4-9
ii  kmod 23-2
ii  udev 232-22

Versions of packages initramfs-tools-core recommends:
ii  busybox  1:1.22.0-19+b3

Versions of packages initramfs-tools-core suggests:
ii  bash-completion  1:2.1-4.3

-- no debconf information