Hi Coiby,
it's a little bit frustrating to have those limitations but
unfortunately it's the best that can be achieved with a reasonable
effort...
There are a few typos. But other than that
Reviewed-by: Philipp Rudo <prudo(a)redhat.com>
On Mon, 21 Feb 2022 15:21:14 +0800
Coiby Xu <coxu(a)redhat.com> wrote:
When updating kernel arg in /etc/default/grub, grubby will replace
the
given arg with new value if the arg is the last one. If given arg isn't
the last one, it would insert it in the end. So it's quite likely there are
multiple values for the same kernel arg. e.g
GRUB_CMDLINE_LINUX="crashkernel=110M crashkernel=220M fadump=on
crashkernel=330M".
So all values should be removed when removing a kernel arg from
/etc/default/grub.
Now _update_kernel_cmdline_in_grub_etc_default is split into
{_add,_remove}_kernel_arg_in_grub_etc_default to address this case.
How about:
When updating the kernel command line in /etc/default/grub, grubby only
replaces a given entry if it is the last entry on the command line.
In all other cases it appends a new entry to it. This behavior makes it
quite likely that there are multiple entries of the same parameter on
the command line, e.g.
GRUB_CMDLINE_LINUX="crashkernel=110M crashkernel=220M fadump=on
crashkernel=330M".
In such an situation _update_kernel_cmdline_in_grub_etc_default only
updates/removes the first entry. Which is usually not what you
want as the kernel (for crashkernel) takes the last entry it can find.
Thus make sure the case with multiple entries of the same parameter is
handled properly. To make implementation easier split
_update_kernel_cmdline_in_grub_etc_default into
{_add,_remove}_kernel_arg_in_grub_etc_default.
Note
1. to be consist with grubby, _add_kernel_arg_in_grub_etc_default will
always make sure the new value appears in the end
2. sed command group and conditional control hasn't bee used to get rid of
grep.
s/hasn't bee/has been/
3. Fully supporting kernel cmdline as documented in
Documentation/admin-guide/kernel-parameters.rst is complex and in
foreseeable future a full implementation is not needed. So simply
document the unsupported cases instead.
Reported-by: Philipp Rudo <prudo(a)redhat.com>
Suggested-by: Philipp Rudo <prudo(a)redhat.com>
Signed-off-by: Coiby Xu <coxu(a)redhat.com>
---
kdumpctl | 85 ++++++++++++++++++++++++++++++++++++++++++++++----------
1 file changed, 70 insertions(+), 15 deletions(-)
diff --git a/kdumpctl b/kdumpctl
index 9fd76ac..d9edc4b 100755
--- a/kdumpctl
+++ b/kdumpctl
@@ -1399,25 +1399,77 @@ _get_all_kernels_from_grubby()
}
GRUB_ETC_DEFAULT="/etc/default/grub"
-# modify the kernel command line parameter in default grub conf
+# Add a kernel arguement in default grub conf
+#
+# As is the same with grubby, this function would replace the given parameter
+# with new value if given parameter appears in the end. Otherwise, it insert
+# the entry in the end.
+#
+# Note as similar to grubby, this function doesn't address the following cases
+# either,
+# 1. The kernel ignores everything on the command line after a '--'. So
+# simply adding the the new entry to the end will fail if the cmdline
s/the the/the/
+# contains a --.
+# 2. If the value for a parameter contains spaces it can be quoted using
+# double quotes, for example param="value with spaces". This will
+# break the [^[:space:]\"] regex for the value.
+# 3. Dashes and underscores in the parameter name are equivalent. So
+# some_parameter and some-parameter are identical.
+# 4. multiple variables have the same name but with different values
+# e.g. efivar_ssdt
How about:
4. Some parameters, e.g. efivar_ssdt, can be given multiple times.
Thanks
Philipp
+# Besides, this function doesn't support adding a kernel
parameter
+# that doesn't have a value
#
# $1: the name of the kernel command line parameter
# $2: new value. If empty, the parameter would be removed
-_update_kernel_cmdline_in_grub_etc_default()
+_add_kernel_arg_in_grub_etc_default()
{
- local _para=$1 _val=$2 _para_val _regex
+ local _para=$1 _val=$2 _para_val
- if [[ -n $_val ]]; then
- _para_val="$_para=$_val"
+ if [[ -z $_val ]]; then
+ derror "value not specified for $_para"
+ return 1
fi
- _regex='^(GRUB_CMDLINE_LINUX=.*)([[:space:]"])'"$_para"'=[^[:space:]"]*(.*)$'
- if grep -q -E "$_regex" "$GRUB_ETC_DEFAULT"; then
- sed -i -E
's/'"$_regex"'/\1\2'"$_para_val"'\3/'
"$GRUB_ETC_DEFAULT"
- elif [[ -n $_para_val ]]; then
- # If the kernel parameter doesn't exist, put it in the first
- sed -i -E 's/^(GRUB_CMDLINE_LINUX=")/\1'"$_para_val"'
/' "$GRUB_ETC_DEFAULT"
- fi
+ _para_val="$_para=$_val"
+ # Update the command line /etc/default/grub, i.e.
+ # on the line that starts with 'GRUB_CMDLINE_LINUX=',
+ # 1) if given parameter appear in the end, replace it with new entry
+ # 2) otherwise, insert the entry in the end
+ sed -i -E "/^GRUB_CMDLINE_LINUX=/ {
+
s/([[:space:]\"])${_para}=[^[:space:]\"]*[[:space:]]*\"$/\1${_para_val}\"/;
+ # t: jump to a label only if a s/// command has succeeded.
+ # Since there is no label, it would jump to the end i.e.
+ # skip the last command if the parameter already exists
+ t;
+ s/\"$/ ${_para_val}\"/
+ }" "$GRUB_ETC_DEFAULT"
+}
+
+# Remove a kernel argument from default grub conf
+#
+# Note removing a kernel parameter that doesn't have a value isn't supported
+# e.g. quiet.
+#
+# $1: the name of the kernel parameter
+_remove_kernel_arg_in_grub_etc_default()
+{
+ local _para=$1
+
+ # On the line that starts with 'GRUB_CMDLINE_LINUX=' do
+ # 1) remove $para=$val if the it's the first arg
+ # 2) remove all occurences of $para=$val
+ # 3) remove duplicate spaces left over by 1) or 2)
+ # 4) remove space at the beginning of the string left over by 1) or 2)
+ # 5) remove space at the end of the string left over by 1) or 2)
+ sed -i -E "/^GRUB_CMDLINE_LINUX=/ {
+ s/\"${_para}=[^[:space:]\"]*/\"/g;
+ s/[[:space:]]+${_para}=[^[:space:]\"]*/ /g;
+ s/[[:space:]]+/ /g;
+ s/(\")[[:space:]]+/\1/g;
+ s/[[:space:]]+(\")/\1/g;
+ }" "$GRUB_ETC_DEFAULT"
}
reset_crashkernel()
@@ -1496,10 +1548,13 @@ reset_crashkernel()
# - set the dump mode as kdump for non-ppc64le cases
# - retrieved the default crashkernel value for given dump mode
if [[ $_grubby_kernel_path == ALL && -n $_dump_mode ]]; then
- _update_kernel_cmdline_in_grub_etc_default crashkernel "$_crashkernel"
+ _add_kernel_arg_in_grub_etc_default crashkernel "$_crashkernel"
# remove the fadump if fadump is disabled
- [[ $_fadump_val == off ]] && _fadump_val=""
- _update_kernel_cmdline_in_grub_etc_default fadump "$_fadump_val"
+ if [[ $_fadump_val == off ]]; then
+ _remove_kernel_arg_in_grub_etc_default fadump
+ else
+ _add_kernel_arg_in_grub_etc_default fadump "$_fadump_val"
+ fi
fi
# If kernel-path not specified, either