RO filesystem startup and NFS netboot

[kleinem]

Hello,

i'm trying to configure my xbian to boot from NFS via a WAN Link, backed by cachefs.
Home will also be mounted via NFS in the future.
The goal is to eliminate SD card writes completely and have one generic Image (xbian filesystem) for multiple raspberrys.
The "identity" (hostname and other stuff) will be set via krb5 keytab during bootup

So for now, i just edited my fstab to look like this:

Code:

# UNCONFIGURED FSTAB FOR BASE SYSTEM
/dev/root             /home                   xbian   subvol=home/@,noatime,nobootwait           0       0
/dev/root             /lib/modules            xbian   ro,subvol=modules/@,noatime,nobootwait        0       0
/dev/root             /                       xbian   ro,noatime,nobootwait                         0       0
/dev/mmcblk0p1        /boot                   xbian   ro,nobootwait                              0       1
none            /run/user                       tmpfs                   noauto                  0       0
none            /run/shm                        tmpfs                   noauto                  0       0
none            /run/lock                       tmpfs                   noauto                  0       0
# custom
none        /var/log            tmpfs            nodev,nosuid,size=10%,mode=1755  0  0
LABEL=cachefs_usb       /var/cache/fscache      ext4                nofail,noatime,user_xattr              0       0

It is working surprisingly well so far BUT
1) Startup is way slower with / mounted ro only.
I suspect this being a result of some processes/scripts requiring write access and waiting to run into timeouts for this operation.

The problem is, i don't see which processes are hung.
Any ideas how i can get proper debugs, which processes require write access?
I'd like to see if i can eliminate their write access by changing startup parameters (logging etc)
Or create a tmpfs mountpoint/symlink if it is absolutely necessary

One of the few bootup messages i'm seeing, seems to be rpcbind/rpc.statd being hung...

2) /var/log does not get mounted after a reboot.
However a mount -a does mount it just fine. Ideas?
3) Is it possible to "Blacklist" the cachefs drive within Kodi, so it does not show up as available media source?

some dmesg output..

Terminal

[ 0.000000] Kernel command line: selinux=0 usbcore.autosuspend=-1 dma.dmachans=0x7f35 bcm2708_fb.fbwidth=720 bcm2708_fb.fbheight=480 bcm2709.boardrev=0xa01041 bcm2709.serial=0x995a07c3 smsc95xx.macaddr=B8:27:EB:5A:07:C3 bcm2708_fb.fbswap=1 bcm2709.disk_led_gpio=47 bcm2709.disk_led_active_low=0 sdhci-bcm2708.emmc_clock_freq=250000000 vc_mem.mem_base=0x3dc00000 vc_mem.mem_size=0x3f000000 telnet zswap.enabled=1 zswap.compressor=lz4 sdhci-bcm2708.sync_after_dma=0 dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootflags=subvol=root/@,thread_pool=2,autodefrag,compress=lz4,commit=120 rootfstype=btrfs rootwait smsc95xx.turbo_mode=N noswap loglevel=3 mod_scsi.scan=sync partswap startevent=mountall nohdparm --startup-event mountall
[ 1.631113] Btrfs loaded
[ 1.631644] Waiting for root device /dev/mmcblk0p2...
[ 1.680424] mmc0: host does not support reading read-only switch, assuming write-enable
[ 1.683989] mmc0: new high speed SDHC card at address aaaa
[ 1.684310] mmcblk0: mmc0:aaaa SL08G 7.40 GiB
[ 1.685989] mmcblk0: p1 p2 p3
[ 1.735328] BTRFS: device label xbian devid 1 transid 363 /dev/root
[ 1.736868] BTRFS info (device mmcblk0p2): enabling auto defrag
[ 1.736893] BTRFS info (device mmcblk0p2): disk space caching is enabled
[ 1.736900] BTRFS: has skinny extents
[ 1.763016] BTRFS: detected SSD devices, enabling SSD mode
[ 1.787574] VFS: Mounted root (btrfs filesystem) on device 0:12.
[ 1.789350] devtmpfs: mounted
[ 1.789584] Freeing unused kernel memory: 192K (8066e000 - 8069e000)
[ 1.789591] BFS CPU scheduler v0.460 by Con Kolivas.
[ 1.800935] Indeed it is in host mode hprt0 = 00021501
[ 1.967584] usb 1-1: new high-speed USB device number 2 using dwc_otg
[ 1.967738] Indeed it is in host mode hprt0 = 00001101
[ 2.117136] random: init urandom read with 32 bits of entropy available
[ 2.147828] usb 1-1: New USB device found, idVendor=0424, idProduct=9514
[ 2.147848] usb 1-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 2.148551] hub 1-1:1.0: USB hub found
[ 2.148698] hub 1-1:1.0: 5 ports detected
[ 2.427740] usb 1-1.1: new high-speed USB device number 3 using dwc_otg
[ 2.521174] usb 1-1.1: New USB device found, idVendor=0424, idProduct=ec00
[ 2.521198] usb 1-1.1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
[ 2.523873] smsc95xx v1.0.4
[ 2.570066] smsc95xx 1-1.1:1.0 eth0: register 'smsc95xx' at usb-bcm2708_usb-1.1, smsc95xx USB 2.0 Ethernet, b8:27:eb:5a:07:c3
[ 2.647642] usb 1-1.5: new high-speed USB device number 4 using dwc_otg
[ 2.741303] usb 1-1.5: New USB device found, idVendor=0781, idProduct=5571
[ 2.741316] usb 1-1.5: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 2.741327] usb 1-1.5: Product: Cruzer Fit
[ 2.741336] usb 1-1.5: Manufacturer: SanDisk
[ 2.741347] usb 1-1.5: SerialNumber: 4C530001170129104171
[ 2.741961] usb-storage 1-1.5:1.0: USB Mass Storage device detected
[ 2.742402] scsi host0: usb-storage 1-1.5:1.0
[ 3.745302] scsi 0:0:0:0: Direct-Access SanDisk Cruzer Fit 1.27 PQ: 0 ANSI: 6
[ 3.747167] sd 0:0:0:0: [sda] 30529536 512-byte logical blocks: (15.6 GB/14.5 GiB)
[ 3.748835] sd 0:0:0:0: [sda] Write Protect is off
[ 3.748855] sd 0:0:0:0: [sda] Mode Sense: 43 00 00 00
[ 3.749179] sd 0:0:0:0: [sda] Write cache: disabled, read cache: enabled, doesn't support DPO or FUA
[ 3.764462] sda: unknown partition table
[ 3.766889] sd 0:0:0:0: [sda] Attached SCSI removable disk
[ 4.447423] BTRFS info (device mmcblk0p2): disk space caching is enabled
[ 5.294803] init: autofs main process (338) terminated with status 1
[ 5.295112] init: autofs main process ended, respawning
[ 5.414268] init: autofs main process (436) terminated with status 1
[ 5.414512] init: autofs main process ended, respawning
[ 5.457618] ------------[ cut here ]------------
[ 5.457688] WARNING: CPU: 3 PID: 429 at fs/sync.c:55 sync_filesystem+0xa4/0xac()
[ 5.457712] Modules linked in:
[ 5.457757] CPU: 3 PID: 429 Comm: mount Not tainted 3.18.8+ #1
[ 5.457812] [<80014334>] (unwind_backtrace) from [<800112fc>] (show_stack+0x10/0x14)
[ 5.457844] [<800112fc>] (show_stack) from [<804d9568>] (dump_stack+0x80/0xcc)
[ 5.457873] [<804d9568>] (dump_stack) from [<80028180>] (warn_slowpath_common+0x64/0x88)
[ 5.457900] [<80028180>] (warn_slowpath_common) from [<800281c0>] (warn_slowpath_null+0x1c/0x24)
[ 5.457922] [<800281c0>] (warn_slowpath_null) from [<800f8a88>] (sync_filesystem+0xa4/0xac)
[ 5.457947] [<800f8a88>] (sync_filesystem) from [<801da3e0>] (btrfs_remount+0x60/0x45c)
[ 5.457968] [<801da3e0>] (btrfs_remount) from [<801db070>] (btrfs_mount+0x894/0x918)
[ 5.457996] [<801db070>] (btrfs_mount) from [<800d5570>] (mount_fs+0x14/0xc4)
[ 5.458022] [<800d5570>] (mount_fs) from [<800ec6f0>] (vfs_kern_mount+0x4c/0xec)
[ 5.458045] [<800ec6f0>] (vfs_kern_mount) from [<800eed6c>] (do_mount+0x180/0x970)
[ 5.458065] [<800eed6c>] (do_mount) from [<800ef870>] (SyS_mount+0x74/0xa0)
[ 5.458087] [<800ef870>] (SyS_mount) from [<8000e560>] (ret_fast_syscall+0x0/0x30)
[ 5.458099] ---[ end trace 7c1c48559aa8b0b9 ]---
[ 5.458116] BTRFS info (device mmcblk0p2): disk space caching is enabled
[ 5.506700] init: autofs main process (453) terminated with status 1
[ 5.506923] init: autofs main process ended, respawning
[ 5.550369] init: xbian-failaccess main process (231) killed by TERM signal
[ 5.617471] smsc95xx 1-1.1:1.0 eth0: hardware isn't capable of remote wakeup
[ 5.627109] init: autofs main process (490) terminated with status 1
[ 5.627344] init: autofs main process ended, respawning
[ 5.705029] init: autofs main process (502) terminated with status 1
[ 5.705215] init: autofs main process ended, respawning
[ 5.789101] init: autofs main process (521) terminated with status 1
[ 5.789373] init: autofs main process ended, respawning
[ 5.871220] init: mountall main process (537) terminated with status 2
[ 5.880287] init: autofs main process (538) terminated with status 1
[ 5.880527] init: autofs main process ended, respawning
[ 6.010215] init: autofs main process (572) terminated with status 1
[ 6.010406] init: autofs main process ended, respawning
[ 6.084346] init: autofs main process (583) terminated with status 1
[ 6.084544] init: autofs main process ended, respawning
[ 6.159220] init: autofs main process (594) terminated with status 1
[ 6.159412] init: autofs main process ended, respawning
[ 6.234256] init: autofs main process (605) terminated with status 1
[ 6.234458] init: autofs respawning too fast, stopped
[ 7.229772] smsc95xx 1-1.1:1.0 eth0: link up, 100Mbps, full-duplex, lpa 0x41E1
[ 11.164443] random: nonblocking pool is initialized
[ 82.617365] vchiq: vchiq_init_state: slot_zero = 0xae080000, is_master = 0
[ 82.672032] udevd[870]: starting version 175
[ 82.948330] bcm2708_spi bcm2708_spi.0: master is unqueued, this is deprecated
[ 82.949071] bcm2708_spi bcm2708_spi.0: SPI Controller at 0x3f204000 (irq 80)
[ 82.962198] bcm2708_i2c_init_pinmode(1,2)
[ 82.962222] bcm2708_i2c_init_pinmode(1,3)
[ 82.962871] bcm2708_i2c bcm2708_i2c.1: BSC1 Controller at 0x3f804000 (irq 79) (baudrate 100000)
[ 83.340942] pcm512x 1-004d: Failed to reset device: -5
[ 83.341020] pcm512x: probe of 1-004d failed with error -5
[ 83.341384] pcm512x 1-004c: Failed to reset device: -5
[ 83.341443] pcm512x: probe of 1-004c failed with error -5
[ 88.915776] init: anacron main process (1475) terminated with status 1
[ 89.038669] EXT4-fs (sda): mounted filesystem with ordered data mode. Opts: user_xattr
[ 89.159693] FS-Cache: Loaded
[ 89.165342] CacheFiles: Loaded
[ 89.320285] FS-Cache: Cache "mycache" added (type cachefiles)
[ 89.320306] CacheFiles: File cache on sda registered
[ 92.297334] init: wait-for-state (xbmcxbmc-loaded) main process (1285) killed by TERM signal
[ 99.350988] init: xbmc-failed-start main process (800) killed by TERM signal
[ 99.372008] init: wait-for-state (zram-swapxbmc-done) main process (1211) killed by TERM signal
[ 99.573027] Adding 250876k swap on /dev/mmcblk0p3. Priority:0 extents:1 across:250876k SSFS
[ 104.553610] init: anacron main process (1926) terminated with status 1

[deHakkelaar]

Maybe of help:
http://wiki.xbian.org/doku.php/installation_nfs