I want to monitor /var/log/syslog
for any changes in realtime (or within-a-few-seconds-of-time), but tail -f
won't update with any new changes.
I'm running Ubuntu-based Linux Mint 17 XFCE live now, but this hasn't worked on live iso's of Ubuntu, Xubuntu, or Linux Mint Mate either.
I've tried these:
$ tail -f /var/log/syslog
$ tail -f --retry -s 1 /var/log/syslog
$ tail --follow=name /var/log/syslog
$ tail --follow=name --retry /var/log/syslog
$ tail --follow=name --retry -s 1 /var/log/syslog
But it only initially outputs the last few lines of the file, then no updates when the file grows (when, for example, trying to mount an empty file gives about 15 lines of errors).
Actually, even trying to follow a test file in my home folder doesn't seem to work, running tail -f testfile
and then (in another terminal):
$ echo "new stuff" >> testfile
$ echo "new stuff2" >> testfile
$ echo "3" >> testfile
doesn't result in any updates to tail
either…
But if I put testfile
in /tmp
(mounted on a tmpfs) then it does follow the file's changes.
Why won't tail follow?
Is there something weird about running live, or overlayfs that cripples tail -f
? And any suggestions how to follow the log? (xwatch
works ok, anything better or in terminal?)
I've tried running strace tail -f -s 1 testfile
and here are the last couple lines of output, after it write(1,
's the existing couple lines of testfile
:
write(1, "new1\n", 5new1
) = 5
fstat64(3, {st_mode=S_IFREG|0644, st_size=22, ...}) = 0
fstatfs64(3, 84, {f_type=0x1021994, f_bsize=4096, f_blocks=968776, f_bfree=461437, f_bavail=461437, f_files=203469, f_ffree=190635, f_fsid={0, 0}, f_namelen=255, f_frsize=4096, f_flags=1056}) = 0
inotify_init() = 4
inotify_add_watch(4, "testfile", IN_MODIFY|IN_ATTRIB|IN_DELETE_SELF|IN_MOVE_SELF) = 1
fstat64(3, {st_mode=S_IFREG|0644, st_size=22, ...}) = 0
read(4,
Best Answer
tail
usesinotify
which does not work withoverlayfs
See this bug report and this discussion. @Xen2050 pointed out the---disable-inotify
switch totail
See this workaroundYou could use
apt-src
to install thecoreutils
source, and recompiletail
with-UHAVE_INOTIFY