File Permissions
Action | --- | r-- | -w- | --x | rw- | r-x | -wx | rwx | r-s |
read - cat file | no | yes | no | no | yes | yes | no | yes | |
write - ls /tmp >> file | no | no | yes | no | yes | no | yes | yes | |
write - ls /tmp > file | no | no | yes | no | yes | no | yes | yes | |
remove file | yes* | yes* | yes | yes* | yes | yes* | yes | yes | |
executing a script | no | no | no | no | no | yes | no | yes | yes** |
yes*: These files gave a "rm: remove write-protected file 'filename'?" error. Saying "yes" removes these files. Also performing a "rm -rf" file removes the file without any warning. The ability to remove a file is controlled at the directory level.
yes**: execute a file with permission of owner or group
Directory Permissions
Action | --- | r-- | -w- | --x | rw- | r-x | -wx | rwx |
cd into directory | no | no | no | yes | no | yes | yes | yes |
ls directory | no | yes* | no | no | yes* | yes | no | yes |
file name completion | no | yes | no | no | yes | yes | no | yes |
create new file in dir. | no | no | no | no | no | no | yes | yes |
read file in dir. | no | no | no | yes | no | yes | yes | yes |
modify file in dir. | no | no | no | yes | no | yes | yes | yes |
remove files | no | no | no | no | no | no | yes | yes |
execute script | no | no | no | yes | no | yes | yes | yes |
ls = yes* - Only the files are listed with error. No other file attributes are able to be listed. File name completion works in these cases as well.
t - Save text attribute (sticky bit): The user may delete or modify only those files in the directory that they own or have write permission for (/tmp).
s - Set group ID: files in that directory will have the group ownership as the directory, instead of than the group of the user that created the file
If you want to have full access to a directory with 2 different users in different groups make a new group and add both users.
addgroup newgroup
adduser user1 newgroup
adduser user2 newgroup
chown root:newgroup /directory
chmod 775 /directory
You do not need to use group ID (s-Flag).
You can use these commands to set 755 on directories and 644 on files
find -type f -exec chmod 644 {} \;
find -type d -exec chmod 755 {} \;
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sudo sysctl vm.block_dump=1
or
echo 1 > /proc/sys/vm/block_dump
tail -f /var/log/kern.log
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apt-get install ntfs-g3
/etc/group
+fuse:x:100:users
vol_id /dev/sda1
/etc/fstab
UUID=5EFC7B02FC7AD42D /media/usbhdd ntfs-3g rw,users,uid=1000,guid=1000,umask=007,locale=de_AT.utf8,force 0 0user can mount but not unmount
https://bugs.launchpad.net/ubuntu/+source/util-linux/+bug/71609/comments/7
wget http://launchpadlibrarian.net/7435949/u ... ount.patch
$ sudo apt-get update
$ sudo apt-get install build-essential
$ sudo apt-get build-dep mount
$ cd /tmp
$ apt-get source mount
$ cd util-linux-2.12r
$ ./debian/rules patch
$ patch -Np1 -i ../util-linux_user_mount.patch
$ ./configure
$ make lib
$ make -C mount
$ sudo chown root:root mount/umount
$ sudo chmod 4755 mount/umount
$ sudo mv mount/umount /bin
automount with udev:
06-usbsticks.rules
BUS=="usb", KERNEL=="sd*", SYSFS{serial}=="DEF10000CC2DAB6", NAME="%k", run+="/bin/mount /media/usbhdd"
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First computer where to redirect serial via TCP:
stty -F /dev/ttyS0 raw 9600 -echo
nc 192.168.0.1 1111 >/dev/ttyS0 </dev/ttyS0
Second computer receiving needs 2 serial's
stty -F /dev/ttyS0 raw 9600 -echo
stty -F /dev/ttyS1 raw 9600 -echo
nc -l -p 1111 >/dev/ttyS1 </dev/ttyS1
Now a programm can connect to /dev/ttyS0 and talks to out first computer.
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What i want from a raid1:
notiy if a disk fails
This is done by mdadm
boot degraded with only one disk
boot degraded does not work with ubuntu, because mdadm does not start a degraded raid
my workaround is to add a bootmenue entry in grub
title Ubuntu, kernel 2.6.20-16-generic (raid defect)
root (hd0,1)
kernel /boot/vmlinuz-2.6.20-16-generic root=/dev/md1 ro raid_degraded
initrd /boot/initrd.img-2.6.20-16-generic
and make an initrd (update-innitramfs -u) with /etc/initramfs-tools/scripts/init-premount/raid_degraded
#!/bin/sh
set -eu
PREREQ="udev"
prereqs()
{
echo "$PREREQ"
}
case ${1:-} in
prereqs)
prereqs
exit 0
;;
*)
. /scripts/functions
;;
esac
if [ -e /scripts/local-top/md ]; then
log_warning_msg "old md initialisation script found, getting out of its way..."
exit 1
fi
MDADM=$(command -v mdadm)
[ -x $MDADM ] || exit 0
if grep raid_degraded /proc/cmdline 2>/dev/null; then
echo "MD_DEGRADED_ARGS=' '" >> /conf/md.conf
fi
exit 0
reported to ubuntu https://bugs.launchpad.net/ubuntu/+source/mdadm/+bug/120375
easy change disk if one disk fails
Threrefore i made a script doing partitioning, adding to raid and installing bootloader of the new disk
#!/bin/sh
if grep -q sda /proc/mdstat; then
SRC_DISK=/dev/sda
DST_DISK=/dev/sdb
else
SRC_DISK=/dev/sdb
DST_DISK=/dev/sda
fi
if ! sfdisk -l 2>/dev/null | grep -q $SRC_DISK; then
echo $SRC_DISK not found
exit 1
fi
if ! sfdisk -l 2>/dev/null | grep -q $DST_DISK; then
echo $DST_DISK not found
exit 1
fi
sfdisk -d $SRC_DISK | sfdisk $DST_DISK
mdadm /dev/md0 -a ${DST_DISK}1
mdadm /dev/md1 -a ${DST_DISK}2
cat /proc/mdstat
/usr/sbin/grub --batch --device-map=/dev/null <<EOF
device (hd0) $DST_DISK
root (hd0,1)
setup (hd0)
quit
EOF
exit 0
set uuid
ubuntu cannot boot if any uuid of any disk is different - solution set uuid:
mdadm --stop /dev/md0
madmd --assemble --verbose /dev/md0 /dev/hda1 /dev/hdb1 \
--update=uuid --uuid=xxxxxxxx:xxxxxxxx:xxxxxxxx:xxxxxxxx
newer versions of mdadm should be able to set uuid with --create
why is my raid1 so slow ?
Reading from my raid1 is as fast as a single sata disc:
hdparm -t /dev/sda1
/dev/sda1:
Timing buffered disk reads: 172 MB in 3.00 seconds = 57.27 MB/sec
hdparm -t /dev/sdb1
/dev/sdb1:
Timing buffered disk reads: 172 MB in 3.01 seconds = 57.20 MB/sec
hdparm -t /dev/md0
/dev/md0:
Timing buffered disk reads: 172 MB in 3.00 seconds = 57.29 MB/sec
i tried
* different motherboard with a different sata onboard controller but also the same results
* different ubuntu kernels: 2.6.17, 2.60.20 and from gutsy 2.6.22rc
* different images:
linux-image-2.6.20-16-generic 2.6.20-16.29
linux-image-2.6.20-16-lowlatency 2.6.20-16.29
linux-image-2.6.20-16-server 2.6.20-16.29
* also a raid1 with PATA Disks
reported to ubuntu https://bugs.launchpad.net/ubuntu/+source/mdadm/+bug/120378
can anybody explain me why?
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