| Message ID | 20210806192714.2562231-1-stijn@linux-ipv6.be |
|---|---|
| State | Changes Requested |
| Delegated to: | Stijn Tintel |
| Headers | show |
| Series | base-files: add option to make /var persistent | expand |
On 06/08/21 21:27, Stijn Tintel wrote: > In OpenWrt, /var is symlinked to /tmp by default. This is done to reduce > the amount of writes to the flash chip, which often don't have the > greatest durability. As a result, things like DHCP or UPnP lease files, > are not persistent across reboots. > > Since OpenWrt can run on devices with more durable storage, it makes > sense to have an option for a persistent /var. Add an option to make > /var persistent. When enabled, /var will no longer be symlinked to /tmp, > but /var/run will be symlink to /tmp/run, as it should contain only > files that should not be kept during reboot. The option is off by > default, to maintain the current behaviour. > Since it does not really need to recompile anything, I think it can/should be handled as a package, not as a compile option. When you install the package these operations are executed, if you remove the package they are undone. -Alberto
On 7/08/2021 02:56, Alberto Bursi wrote: > > > On 06/08/21 21:27, Stijn Tintel wrote: >> In OpenWrt, /var is symlinked to /tmp by default. This is done to reduce >> the amount of writes to the flash chip, which often don't have the >> greatest durability. As a result, things like DHCP or UPnP lease files, >> are not persistent across reboots. >> >> Since OpenWrt can run on devices with more durable storage, it makes >> sense to have an option for a persistent /var. Add an option to make >> /var persistent. When enabled, /var will no longer be symlinked to /tmp, >> but /var/run will be symlink to /tmp/run, as it should contain only >> files that should not be kept during reboot. The option is off by >> default, to maintain the current behaviour. >> > > Since it does not really need to recompile anything, I think it > can/should be handled as a package, not as a compile option. > > When you install the package these operations are executed, if you > remove the package they are undone. Removing /var at runtime, which basically happens when you remove the symlink, is very ugly and has a huge potential for breakage. Having it as a build option also avoids users from accidentally installing it as a package. If you disagree, please elaborate further, including measures to avoid random breakage caused by removing /var at runtime. Thanks, Stijn
On 07/08/21 02:46, Stijn Tintel wrote: > On 7/08/2021 02:56, Alberto Bursi wrote: >> >> >> On 06/08/21 21:27, Stijn Tintel wrote: >>> In OpenWrt, /var is symlinked to /tmp by default. This is done to reduce >>> the amount of writes to the flash chip, which often don't have the >>> greatest durability. As a result, things like DHCP or UPnP lease files, >>> are not persistent across reboots. >>> >>> Since OpenWrt can run on devices with more durable storage, it makes >>> sense to have an option for a persistent /var. Add an option to make >>> /var persistent. When enabled, /var will no longer be symlinked to /tmp, >>> but /var/run will be symlink to /tmp/run, as it should contain only >>> files that should not be kept during reboot. The option is off by >>> default, to maintain the current behaviour. >>> >> >> Since it does not really need to recompile anything, I think it >> can/should be handled as a package, not as a compile option. >> >> When you install the package these operations are executed, if you >> remove the package they are undone. > > Removing /var at runtime, which basically happens when you remove the > symlink, is very ugly and has a huge potential for breakage. Having it > as a build option also avoids users from accidentally installing it as a > package. If you disagree, please elaborate further, including measures > to avoid random breakage caused by removing /var at runtime. > My focus was more on "not using a compile option", I don't think it's necessary to do this at runtime. A simple measure to avoid breakage would be to add something that runs on boot (either initscript or preinitscript) to do these changes before any other service that needs that folder is started. So you install the package and then reboot. This approach also allows to make this a permanent change (not an optional package) and control this function with UCI config, just change the setting and reboot. IMHO this is good enough for most users, and much better than having to recompile or do the change manually. For the sake of completeness, (also shameless plug about my project): A more complex way to do it at runtime that avoids breakage is bind mounting the original folder somewhere else so you can sync the contents with the new/empty folder, then restarting all services that need it. See https://github.com/bobafetthotmail/folder2ram/blob/master/debian_package/sbin/folder2ram#L658 (the service restart is not included in that script since it has no way of knowing what services need the folders, this operation is left to the user or for OpenMediaVault it's handled by the plugin that also writes the configuration) > Thanks, > Stijn > > > _______________________________________________ > openwrt-devel mailing list > openwrt-devel@lists.openwrt.org > https://lists.openwrt.org/mailman/listinfo/openwrt-devel >
On 7/08/2021 10:05, Alberto Bursi wrote: > > > On 07/08/21 02:46, Stijn Tintel wrote: >> On 7/08/2021 02:56, Alberto Bursi wrote: >>> >>> >>> On 06/08/21 21:27, Stijn Tintel wrote: >>>> In OpenWrt, /var is symlinked to /tmp by default. This is done to >>>> reduce >>>> the amount of writes to the flash chip, which often don't have the >>>> greatest durability. As a result, things like DHCP or UPnP lease >>>> files, >>>> are not persistent across reboots. >>>> >>>> Since OpenWrt can run on devices with more durable storage, it makes >>>> sense to have an option for a persistent /var. Add an option to make >>>> /var persistent. When enabled, /var will no longer be symlinked to >>>> /tmp, >>>> but /var/run will be symlink to /tmp/run, as it should contain only >>>> files that should not be kept during reboot. The option is off by >>>> default, to maintain the current behaviour. >>>> >>> >>> Since it does not really need to recompile anything, I think it >>> can/should be handled as a package, not as a compile option. >>> >>> When you install the package these operations are executed, if you >>> remove the package they are undone. >> >> Removing /var at runtime, which basically happens when you remove the >> symlink, is very ugly and has a huge potential for breakage. Having it >> as a build option also avoids users from accidentally installing it as a >> package. If you disagree, please elaborate further, including measures >> to avoid random breakage caused by removing /var at runtime. >> > > My focus was more on "not using a compile option", I don't think it's > necessary to do this at runtime. > > A simple measure to avoid breakage would be to add something that runs > on boot (either initscript or preinitscript) to do these changes > before any other service that needs that folder is started. > So you install the package and then reboot. > > This approach also allows to make this a permanent change (not an > optional package) and control this function with UCI config, just > change the setting and reboot. > > IMHO this is good enough for most users, and much better than having > to recompile or do the change manually. > > > For the sake of completeness, (also shameless plug about my project): > A more complex way to do it at runtime that avoids breakage is bind > mounting the original folder somewhere else so you can sync the > contents with the new/empty folder, then restarting all services that > need it. > See > https://github.com/bobafetthotmail/folder2ram/blob/master/debian_package/sbin/folder2ram#L658 > > (the service restart is not included in that script since it has no > way of knowing what services need the folders, this operation is left > to the user or for OpenMediaVault it's handled by the plugin that also > writes the configuration) > Appreciate the input. It still sounds overly complex compared to my suggestion, especially for something that most users will probably not use. I don't feel comfortable implementing something like that. I'll just keep using my patch locally then, as I have done for almost five years. Thanks, Stijn
The sender domain has a DMARC Reject/Quarantine policy which disallows sending mailing list messages using the original "From" header. To mitigate this problem, the original message has been wrapped automatically by the mailing list software. On 8/7/21 10:40 AM, Stijn Tintel wrote: > > On 7/08/2021 10:05, Alberto Bursi wrote: >> >> >> On 07/08/21 02:46, Stijn Tintel wrote: >>> On 7/08/2021 02:56, Alberto Bursi wrote: >>>> >>>> >>>> On 06/08/21 21:27, Stijn Tintel wrote: >>>>> In OpenWrt, /var is symlinked to /tmp by default. This is done to >>>>> reduce >>>>> the amount of writes to the flash chip, which often don't have the >>>>> greatest durability. As a result, things like DHCP or UPnP lease >>>>> files, >>>>> are not persistent across reboots. >>>>> >>>>> Since OpenWrt can run on devices with more durable storage, it makes >>>>> sense to have an option for a persistent /var. Add an option to make >>>>> /var persistent. When enabled, /var will no longer be symlinked to >>>>> /tmp, >>>>> but /var/run will be symlink to /tmp/run, as it should contain only >>>>> files that should not be kept during reboot. The option is off by >>>>> default, to maintain the current behaviour. >>>>> >>>> >>>> Since it does not really need to recompile anything, I think it >>>> can/should be handled as a package, not as a compile option. >>>> >>>> When you install the package these operations are executed, if you >>>> remove the package they are undone. >>> >>> Removing /var at runtime, which basically happens when you remove the >>> symlink, is very ugly and has a huge potential for breakage. Having it >>> as a build option also avoids users from accidentally installing it as a >>> package. If you disagree, please elaborate further, including measures >>> to avoid random breakage caused by removing /var at runtime. >>> >> >> My focus was more on "not using a compile option", I don't think it's >> necessary to do this at runtime. >> >> A simple measure to avoid breakage would be to add something that runs >> on boot (either initscript or preinitscript) to do these changes >> before any other service that needs that folder is started. >> So you install the package and then reboot. >> >> This approach also allows to make this a permanent change (not an >> optional package) and control this function with UCI config, just >> change the setting and reboot. >> >> IMHO this is good enough for most users, and much better than having >> to recompile or do the change manually. >> >> >> For the sake of completeness, (also shameless plug about my project): >> A more complex way to do it at runtime that avoids breakage is bind >> mounting the original folder somewhere else so you can sync the >> contents with the new/empty folder, then restarting all services that >> need it. >> See >> https://github.com/bobafetthotmail/folder2ram/blob/master/debian_package/sbin/folder2ram#L658 >> >> (the service restart is not included in that script since it has no >> way of knowing what services need the folders, this operation is left >> to the user or for OpenMediaVault it's handled by the plugin that also >> writes the configuration) >> > > Appreciate the input. It still sounds overly complex compared to my > suggestion, especially for something that most users will probably not > use. I don't feel comfortable implementing something like that. I'll > just keep using my patch locally then, as I have done for almost five > years. > I would love to see your patch it in de main tree. It is a nice addition for everyone using extroot (like me). Even without extroot and current flashes, it might be worthwile to enable this and make thinks like dhcp leases persistent. In a soho network, they don't change that often to wear out a flash. > Thanks, > Stijn > > > _______________________________________________ > openwrt-devel mailing list > openwrt-devel@lists.openwrt.org > https://lists.openwrt.org/mailman/listinfo/openwrt-devel
On 07/08/21 10:40, Stijn Tintel wrote: > > On 7/08/2021 10:05, Alberto Bursi wrote: >> >> >> On 07/08/21 02:46, Stijn Tintel wrote: >>> On 7/08/2021 02:56, Alberto Bursi wrote: >>>> >>>> >>>> On 06/08/21 21:27, Stijn Tintel wrote: >>>>> In OpenWrt, /var is symlinked to /tmp by default. This is done to >>>>> reduce >>>>> the amount of writes to the flash chip, which often don't have the >>>>> greatest durability. As a result, things like DHCP or UPnP lease >>>>> files, >>>>> are not persistent across reboots. >>>>> >>>>> Since OpenWrt can run on devices with more durable storage, it makes >>>>> sense to have an option for a persistent /var. Add an option to make >>>>> /var persistent. When enabled, /var will no longer be symlinked to >>>>> /tmp, >>>>> but /var/run will be symlink to /tmp/run, as it should contain only >>>>> files that should not be kept during reboot. The option is off by >>>>> default, to maintain the current behaviour. >>>>> >>>> >>>> Since it does not really need to recompile anything, I think it >>>> can/should be handled as a package, not as a compile option. >>>> >>>> When you install the package these operations are executed, if you >>>> remove the package they are undone. >>> >>> Removing /var at runtime, which basically happens when you remove the >>> symlink, is very ugly and has a huge potential for breakage. Having it >>> as a build option also avoids users from accidentally installing it as a >>> package. If you disagree, please elaborate further, including measures >>> to avoid random breakage caused by removing /var at runtime. >>> >> >> My focus was more on "not using a compile option", I don't think it's >> necessary to do this at runtime. >> >> A simple measure to avoid breakage would be to add something that runs >> on boot (either initscript or preinitscript) to do these changes >> before any other service that needs that folder is started. >> So you install the package and then reboot. >> >> This approach also allows to make this a permanent change (not an >> optional package) and control this function with UCI config, just >> change the setting and reboot. >> >> IMHO this is good enough for most users, and much better than having >> to recompile or do the change manually. >> >> >> For the sake of completeness, (also shameless plug about my project): >> A more complex way to do it at runtime that avoids breakage is bind >> mounting the original folder somewhere else so you can sync the >> contents with the new/empty folder, then restarting all services that >> need it. >> See >> https://github.com/bobafetthotmail/folder2ram/blob/master/debian_package/sbin/folder2ram#L658 >> >> (the service restart is not included in that script since it has no >> way of knowing what services need the folders, this operation is left >> to the user or for OpenMediaVault it's handled by the plugin that also >> writes the configuration) >> > > Appreciate the input. It still sounds overly complex compared to my > suggestion, especially for something that most users will probably not > use. I don't feel comfortable implementing something like that. I'll > just keep using my patch locally then, as I have done for almost five > years. > I'm not stopping you, I'm just voicing my opinion. Having this as a compile option is still better than nothing, please don't drop this just because of my feedback. -Alberto
Hi, > --- a/config/Config-images.in > +++ b/config/Config-images.in > @@ -303,4 +303,10 @@ menu "Target Images" > it will be mounted by PARTUUID which makes the kernel > find the > appropriate disk automatically. > > + config TARGET_ROOTFS_PERSIST_VAR > + bool "Make /var persistent" > + default n > + help > + Do not symlink /var to /tmp, so that its content will > + persist across reboots. I'd add information about /var/run here as well, just add something like "(/var/run will still be linked to /tmp/run)" ... Otherwise, the description would be misleading. Best Adrian > endmenu > diff --git a/package/base-files/Makefile b/package/base-files/Makefile index > 5f816a0d1b..687fbc5f78 100644 > --- a/package/base-files/Makefile > +++ b/package/base-files/Makefile > @@ -172,8 +172,13 @@ define Package/base-files/install > mkdir -p $(1)/www > mkdir -p $(1)/root > $(LN) /proc/mounts $(1)/etc/mtab > +ifeq ($(CONFIG_TARGET_ROOTFS_PERSIST_VAR),n) > rm -f $(1)/var > $(LN) tmp $(1)/var > +else > + mkdir $(1)/var > + $(LN) /tmp/run $(1)/var/run > +endif > mkdir -p $(1)/etc > $(LN) /tmp/resolv.conf /tmp/TZ /tmp/localtime $(1)/etc/ > > -- > 2.31.1 > > > _______________________________________________ > openwrt-devel mailing list > openwrt-devel@lists.openwrt.org > https://lists.openwrt.org/mailman/listinfo/openwrt-devel
diff --git a/config/Config-images.in b/config/Config-images.in index 4a7f08824b..dc68fade3c 100644 --- a/config/Config-images.in +++ b/config/Config-images.in @@ -303,4 +303,10 @@ menu "Target Images" it will be mounted by PARTUUID which makes the kernel find the appropriate disk automatically. + config TARGET_ROOTFS_PERSIST_VAR + bool "Make /var persistent" + default n + help + Do not symlink /var to /tmp, so that its content will + persist across reboots. endmenu diff --git a/package/base-files/Makefile b/package/base-files/Makefile index 5f816a0d1b..687fbc5f78 100644 --- a/package/base-files/Makefile +++ b/package/base-files/Makefile @@ -172,8 +172,13 @@ define Package/base-files/install mkdir -p $(1)/www mkdir -p $(1)/root $(LN) /proc/mounts $(1)/etc/mtab +ifeq ($(CONFIG_TARGET_ROOTFS_PERSIST_VAR),n) rm -f $(1)/var $(LN) tmp $(1)/var +else + mkdir $(1)/var + $(LN) /tmp/run $(1)/var/run +endif mkdir -p $(1)/etc $(LN) /tmp/resolv.conf /tmp/TZ /tmp/localtime $(1)/etc/
In OpenWrt, /var is symlinked to /tmp by default. This is done to reduce the amount of writes to the flash chip, which often don't have the greatest durability. As a result, things like DHCP or UPnP lease files, are not persistent across reboots. Since OpenWrt can run on devices with more durable storage, it makes sense to have an option for a persistent /var. Add an option to make /var persistent. When enabled, /var will no longer be symlinked to /tmp, but /var/run will be symlink to /tmp/run, as it should contain only files that should not be kept during reboot. The option is off by default, to maintain the current behaviour. Signed-off-by: Stijn Tintel <stijn@linux-ipv6.be> --- config/Config-images.in | 6 ++++++ package/base-files/Makefile | 5 +++++ 2 files changed, 11 insertions(+)